[libc++] Replace several uses of 0 by nullptr

[brucem]

More nullptr usage.

[dim]

LGTM minus a few nits, though it would be nice if you can verify that all the changed headers still compile in -std=c++98 and/or -std=gnu++98 mode.

include/functional

1718

The cast can be removed now.

include/valarray

805

Missed __end here?

[jroelofs]

Is it worth adding -Werror=zero-as-null-pointer-constant to the build?

[EricWF]

So my main concern with this patch is that nullptr is actually #defined'ed in C++03 mode. That definition comes from the __nullptr header, and therefore we would need to add that header to each include which uses it. Which kind of sucks.

[dim]

In D43159#1004625, @EricWF wrote:

So my main concern with this patch is that nullptr is actually #defined'ed in C++03 mode. That definition comes from the __nullptr header, and therefore we would need to add that header to each include which uses it. Which kind of sucks.

Indeed, but isn't nullptr used in many headers already? And as far as I can see, none of those includes <__nullptr> explicitly, so the definition must come from some transitive include.

[brucem]

Addressed minor issues.

• Addressed missing __end_ initialization from valarray.
• Removed cast that was no longer needed.
• Added nullptr usage to include/regex.

[brucem]

In D43159#1004639, @dim wrote:

In D43159#1004625, @EricWF wrote:

So my main concern with this patch is that nullptr is actually #defined'ed in C++03 mode. That definition comes from the __nullptr header, and therefore we would need to add that header to each include which uses it. Which kind of sucks.

Indeed, but isn't nullptr used in many headers already? And as far as I can see, none of those includes <__nullptr> explicitly, so the definition must come from some transitive include.

It is handled in the wrapper around stddef.h so it all should just work.

[brucem]

In D43159#1004617, @jroelofs wrote:

Is it worth adding -Werror=zero-as-null-pointer-constant to the build?

I'll look at this as a follow up.

[brucem]

Can we revive this review? I'd still like to land this ...

[mclow.lists]

In D43159#1526170, @brucem wrote:

Can we revive this review? I'd still like to land this ...

What was the result of testing with -std=c++98 and/or -std=gnu++98 ?
The code changes look fine; but as @EricWF said....

[brucem]

Updated to current master and added more nullptr usage.

[brucem]

Remove CMakeLists.txt change.

[zoecarver]

include/memory

1259

This could be nullptr too.

[brucem]

More nullptr-ification.

[brucem]

include/memory

1259

This pointed out a number of things that could be fixed, so did that and updated.

[brucem]

In D43159#1526215, @mclow.lists wrote:

What was the result of testing with -std=c++98 and/or -std=gnu++98 ?
The code changes look fine; but as @EricWF said....

It seems to work for me in -std=c++98 ...

I responded to the point that @EricWF made before ... the __nullptr header is included by the wrapper around stddef.h ... and these aren't the first / only usages of nullptr in the headers.

[brucem]

Updating to current master.

[brucem]

In addition to my previous explanation for the concerns about using nullptr more ... it should be noted that many of these files already use nullptr.

[ldionne]

I'm fine with this given what the author said about nullptr already being used in those headers.

[mclow.lists]

Did you try to build libc++ or run the tests before submitting this?

include/__threading_support

323

This one is wrong.

[mclow.lists]

In <algorithm>, you missed a couple of (value_type*)0. Line 3356, 3369, 3486 and 3499.

[mclow.lists]

include/algorithm

4431

I'm not really a fan of casting nullptr to a value_type *. This change doesn't seem to add anything to the code; it's just longer.

The call to __incr doesn't use the pointer at all. Maybe a better approach is to change

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY void __incr(_Tp*) _NOEXCEPT
    {__incr(integral_constant<bool, is_trivially_destructible<_Tp>::value>());}

to:

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY void __incr() _NOEXCEPT
    {__incr(integral_constant<bool, is_trivially_destructible<_Tp>::value>());}

and remove the nullptrs from the calls in <algorithm>
Alternately, add an overload of __incr that takes a nullptr_t.

[ldionne]

I agree with Marshall's requests.

[mclow.lists]

include/__threading_support

323

__libcpp_thread_t is an alias for an operating-system specific type.
On Mac OS, it is a pointer to some Darwin-specific type.
On Ubuntu, it is a const unsigned long.

You can't compare it to nullptr.

[ldionne]

include/__threading_support

323

I think the comparison should be *__t == __libcpp_thread_t().

[ldionne]

Ping -- is there still interest in moving forward with this? If so, please address the comments and update the patch, otherwise you can abandon the revision to clean up the libc++ review queue.

[ldionne]

Rebase onto master

[ldionne]

Address review comments.

[ldionne]

I'll ship this if CI passes, since I addressed all comments we had originally.

[curdeius]

libcxx/include/memory

4371 ↗

(On Diff #307402)

Unneeded chang for use_count(). It's a long.

[curdeius]

libcxx/include/functional

1759 ↗

(On Diff #307402)

All uses of __f_ should also use nullptr. If my search counted correctly, there are 15 of them in __value_func.

libcxx/include/locale

4335 ↗

(On Diff #307402)

You missed this one.

4340 ↗

(On Diff #307402)

And here.

[ldionne]

Apply review comments. Thanks for the catches!

[curdeius]

LGTM!

include/__locale

 class _LIBCPP_TYPE_VIS ctype<char>
     : public locale::facet, public ctype_base
 {
     const mask* __tab_;
     bool        __del_;
 public:
     typedef char char_type;
 
-    explicit ctype(const mask* __tab = 0, bool __del = false, size_t __refs = 0);
+    explicit ctype(const mask* __tab = nullptr, bool __del = false, size_t __refs = 0);
 
     _LIBCPP_INLINE_VISIBILITY
     bool is(mask __m, char_type __c) const
     {
         return isascii(__c) ? (__tab_[static_cast<int>(__c)] & __m) !=0 : false;
     }
 
     _LIBCPP_INLINE_VISIBILITY

include/__sso_allocator

public:
 
     _LIBCPP_INLINE_VISIBILITY __sso_allocator() throw() : __allocated_(false) {}
     _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator&) throw() : __allocated_(false) {}
     template <class _Up> _LIBCPP_INLINE_VISIBILITY __sso_allocator(const __sso_allocator<_Up, _Np>&) throw()
          : __allocated_(false) {}
 private:
     __sso_allocator& operator=(const __sso_allocator&);
 public:
-    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = 0)
+    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, typename __sso_allocator<void, _Np>::const_pointer = nullptr)
     {
         if (!__allocated_ && __n <= _Np)
         {
             __allocated_ = true;
             return (pointer)&buf_;
         }
         return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
     }

include/__string

 char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
 {
     for (; __n; --__n)
     {
         if (eq(*__s, __a))
             return __s;
         ++__s;
     }
-    return 0;
+    return nullptr;
 }
 
 inline
 char16_t*
 char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
     char_type* __r = __s1;
     if (__s1 < __s2)

 char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
 {
     for (; __n; --__n)
     {
         if (eq(*__s, __a))
             return __s;
         ++__s;
     }
-    return 0;
+    return nullptr;
 }
 
 inline
 char32_t*
 char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
     char_type* __r = __s1;
     if (__s1 < __s2)

 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
 __str_find(const _CharT *__p, _SizeT __sz, 
              _CharT __c, _SizeT __pos) _NOEXCEPT
 {
     if (__pos >= __sz)
         return __npos;
     const _CharT* __r = _Traits::find(__p + __pos, __sz - __pos, __c);
-    if (__r == 0)
+    if (__r == nullptr)
         return __npos;
     return static_cast<_SizeT>(__r - __p);
 }
 
 template <class _CharT, class _Traits>
 inline _LIBCPP_CONSTEXPR_AFTER_CXX11 const _CharT *
 __search_substring(const _CharT *__first1, const _CharT *__last1,
                    const _CharT *__first2, const _CharT *__last2) {
__search_substring(const _CharT *__first1, const _CharT *__last1,
   while (true) {
     __len1 = __last1 - __first1;
     // Check whether __first1 still has at least __len2 bytes.
     if (__len1 < __len2)
       return __last1;
 
     // Find __f2 the first byte matching in __first1.
     __first1 = _Traits::find(__first1, __len1 - __len2 + 1, __f2);
-    if (__first1 == 0)
+    if (__first1 == nullptr)
       return __last1;
 
     // It is faster to compare from the first byte of __first1 even if we
     // already know that it matches the first byte of __first2: this is because
     // __first2 is most likely aligned, as it is user's "pattern" string, and
     // __first1 + 1 is most likely not aligned, as the match is in the middle of
     // the string.
     if (_Traits::compare(__first1, __first2, __len2) == 0)

 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
 __str_find_first_not_of(const _CharT *__p, _SizeT __sz,
                     const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
 {
     if (__pos < __sz)
     {
         const _CharT* __pe = __p + __sz;
         for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
-            if (_Traits::find(__s, __n, *__ps) == 0)
+            if (_Traits::find(__s, __n, *__ps) == nullptr)
                 return static_cast<_SizeT>(__ps - __p);
     }
     return __npos;
 }
 
 
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY

 __str_find_last_not_of(const _CharT *__p, _SizeT __sz,
                    const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
 {
     if (__pos < __sz)
         ++__pos;
     else
         __pos = __sz;
     for (const _CharT* __ps = __p + __pos; __ps != __p;)
-        if (_Traits::find(__s, __n, *--__ps) == 0)
+        if (_Traits::find(__s, __n, *--__ps) == nullptr)
             return static_cast<_SizeT>(__ps - __p);
     return __npos;
 }
 
 
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
 __str_find_last_not_of(const _CharT *__p, _SizeT __sz,

include/__threading_support

 // Returns non-zero if t1 < t2, otherwise 0
 bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
   return t1 < t2;
 }
 
 // Thread
 bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
-  return *__t == 0;
+  return *__t == nullptr;
 }
 
 int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
                            void *__arg)
 {
-  return pthread_create(__t, 0, __func, __arg);
+  return pthread_create(__t, nullptr, __func, __arg);
 }
 
 __libcpp_thread_id __libcpp_thread_get_current_id()
 {
   return pthread_self();
 }
 
 __libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
 {
   return *__t;
 }
 
 int __libcpp_thread_join(__libcpp_thread_t *__t)
 {
-  return pthread_join(*__t, 0);
+  return pthread_join(*__t, nullptr);
 }
 
 int __libcpp_thread_detach(__libcpp_thread_t *__t)
 {
   return pthread_detach(*__t);
 }
 
 void __libcpp_thread_yield()

include/algorithm

 {
     typedef typename iterator_traits<_BirdirectionalIterator>::value_type value_type;
     if (__first1 != __last1)
     {
         __destruct_n __d(0);
         unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
         value_type* __last2 = __first2;
         ::new(__last2) value_type(_VSTD::move(*__first1));
-        __d.__incr((value_type*)0);
+        __d.__incr((value_type*)nullptr);
         for (++__last2; ++__first1 != __last1; ++__last2)
         {
             value_type* __j2 = __last2;
             value_type* __i2 = __j2;
             if (__comp(*__first1, *--__i2))
             {
                 ::new(__j2) value_type(_VSTD::move(*__i2));
-                __d.__incr((value_type*)0);
+                __d.__incr((value_type*)nullptr);
                 for (--__j2; __i2 != __first2 && __comp(*__first1,  *--__i2); --__j2)
                     *__j2 = _VSTD::move(*__i2);
                 *__j2 = _VSTD::move(*__first1);
             }
             else
             {
                 ::new(__j2) value_type(_VSTD::move(*__first1));
-                __d.__incr((value_type*)0);
+                __d.__incr((value_type*)nullptr);
             }
         }
         __h.release();
     }
 }
 
 template <class _Compare, class _RandomAccessIterator>
 void
__buffered_inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
                 typename iterator_traits<_BidirectionalIterator>::value_type* __buff)
 {
     typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
     __destruct_n __d(0);
     unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
     if (__len1 <= __len2)
     {
         value_type* __p = __buff;
-        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)0), (void) ++__i, ++__p)
+        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)nullptr), (void) ++__i, ++__p)
             ::new(__p) value_type(_VSTD::move(*__i));
         __half_inplace_merge(__buff, __p, __middle, __last, __first, __comp);
     }
     else
     {
         value_type* __p = __buff;
-        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)0), (void) ++__i, ++__p)
+        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)nullptr), (void) ++__i, ++__p)
             ::new(__p) value_type(_VSTD::move(*__i));
         typedef reverse_iterator<_BidirectionalIterator> _RBi;
         typedef reverse_iterator<value_type*> _Rv;
         __half_inplace_merge(_Rv(__p), _Rv(__buff),
                              _RBi(__middle), _RBi(__first),
                              _RBi(__last), __invert<_Compare>(__comp));
     }
 }

 {
     typedef typename iterator_traits<_InputIterator1>::value_type value_type;
     __destruct_n __d(0);
     unique_ptr<value_type, __destruct_n&> __h(__result, __d);
     for (; true; ++__result)
     {
         if (__first1 == __last1)
         {
-            for (; __first2 != __last2; ++__first2, ++__result, __d.__incr((value_type*)0))
+            for (; __first2 != __last2; ++__first2, ++__result, __d.__incr((value_type*)nullptr))
                 ::new (__result) value_type(_VSTD::move(*__first2));
             __h.release();
             return;
         }
         if (__first2 == __last2)
         {
-            for (; __first1 != __last1; ++__first1, ++__result, __d.__incr((value_type*)0))
+            for (; __first1 != __last1; ++__first1, ++__result, __d.__incr((value_type*)nullptr))
                 ::new (__result) value_type(_VSTD::move(*__first1));
             __h.release();
             return;
         }
         if (__comp(*__first2, *__first1))
         {
             ::new (__result) value_type(_VSTD::move(*__first2));
-            __d.__incr((value_type*)0);
+            __d.__incr((value_type*)nullptr);
             ++__first2;
         }
         else
         {
             ::new (__result) value_type(_VSTD::move(*__first1));
-            __d.__incr((value_type*)0);
+            __d.__incr((value_type*)nullptr);
             ++__first1;
         }
     }
 }
 
 template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
 void
 __merge_move_assign(_InputIterator1 __first1, _InputIterator1 __last1,
case 1:
         ::new(__first2) value_type(_VSTD::move(*__first1));
         return;
     case 2:
         __destruct_n __d(0);
         unique_ptr<value_type, __destruct_n&> __h2(__first2, __d);
         if (__comp(*--__last1, *__first1))
         {
             ::new(__first2) value_type(_VSTD::move(*__last1));
-            __d.__incr((value_type*)0);
+            __d.__incr((value_type*)nullptr);
             ++__first2;
             ::new(__first2) value_type(_VSTD::move(*__first1));
         }
         else
         {
             ::new(__first2) value_type(_VSTD::move(*__first1));
-            __d.__incr((value_type*)0);
+            __d.__incr((value_type*)nullptr);
             ++__first2;
             ::new(__first2) value_type(_VSTD::move(*__last1));
         }
         __h2.release();
         return;
     }
     if (__len <= 8)
     {
__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
     }
     typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
     _RandomAccessIterator __m = __first + __l2;
     if (__len <= __buff_size)
     {
         __destruct_n __d(0);
         unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
         __stable_sort_move<_Compare>(__first, __m, __comp, __l2, __buff);
-        __d.__set(__l2, (value_type*)0);
+        __d.__set(__l2, (value_type*)nullptr);
         __stable_sort_move<_Compare>(__m, __last, __comp, __len - __l2, __buff + __l2);
-        __d.__set(__len, (value_type*)0);
+        __d.__set(__len, (value_type*)nullptr);
         __merge_move_assign<_Compare>(__buff, __buff + __l2, __buff + __l2, __buff + __len, __first, __comp);
 //         __merge<_Compare>(move_iterator<value_type*>(__buff),
 //                           move_iterator<value_type*>(__buff + __l2),
 //                           move_iterator<_RandomAccessIterator>(__buff + __l2),
 //                           move_iterator<_RandomAccessIterator>(__buff + __len),
 //                           __first, __comp);
         return;
     }

include/bitset

protected:
     typedef __bit_iterator<__bitset, true>             const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __bitset() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     explicit _LIBCPP_CONSTEXPR __bitset(unsigned long long) _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY reference __make_ref(size_t) _NOEXCEPT
-        {return reference(0, 1);}
+        {return reference(nullptr, 1);}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR const_reference __make_ref(size_t) const _NOEXCEPT
-        {return const_reference(0, 1);}
+        {return const_reference(nullptr, 1);}
     _LIBCPP_INLINE_VISIBILITY iterator __make_iter(size_t) _NOEXCEPT
-        {return iterator(0, 0);}
+        {return iterator(nullptr, 0);}
     _LIBCPP_INLINE_VISIBILITY const_iterator __make_iter(size_t) const _NOEXCEPT
-        {return const_iterator(0, 0);}
+        {return const_iterator(nullptr, 0);}
 
     _LIBCPP_INLINE_VISIBILITY void operator&=(const __bitset&) _NOEXCEPT {}
     _LIBCPP_INLINE_VISIBILITY void operator|=(const __bitset&) _NOEXCEPT {}
     _LIBCPP_INLINE_VISIBILITY void operator^=(const __bitset&) _NOEXCEPT {}
 
     _LIBCPP_INLINE_VISIBILITY void flip() _NOEXCEPT {}
 
     _LIBCPP_INLINE_VISIBILITY unsigned long to_ulong() const {return 0;}

include/chrono

#endif
     template <class _Rep2>
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
         explicit duration(const _Rep2& __r,
             typename enable_if
             <
                is_convertible<_Rep2, rep>::value &&
                (treat_as_floating_point<rep>::value ||
                !treat_as_floating_point<_Rep2>::value)
-            >::type* = 0)
+            >::type* = nullptr)
                 : __rep_(__r) {}
 
     // conversions
     template <class _Rep2, class _Period2>
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
         duration(const duration<_Rep2, _Period2>& __d,
             typename enable_if
             <
                 __no_overflow<_Period2, period>::value && (
                 treat_as_floating_point<rep>::value ||
                 (__no_overflow<_Period2, period>::type::den == 1 &&
                  !treat_as_floating_point<_Rep2>::value))
-            >::type* = 0)
+            >::type* = nullptr)
                 : __rep_(_VSTD::chrono::duration_cast<duration>(__d).count()) {}
 
     // observer
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR rep count() const {return __rep_;}
 
     // arithmetic
 
public:
 
     // conversions
     template <class _Duration2>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     time_point(const time_point<clock, _Duration2>& t,
         typename enable_if
         <
             is_convertible<_Duration2, duration>::value
-        >::type* = 0)
+        >::type* = nullptr)
             : __d_(t.time_since_epoch()) {}
 
     // observer
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 duration time_since_epoch() const {return __d_;}
 
     // arithmetic
 

include/fstream

private:
   bool __always_noconv_;
 
   bool __read_mode();
   void __write_mode();
 };
 
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>::basic_filebuf()
-    : __extbuf_(0),
-      __extbufnext_(0),
-      __extbufend_(0),
+    : __extbuf_(nullptr),
+      __extbufnext_(nullptr),
+      __extbufend_(nullptr),
       __ebs_(0),
-      __intbuf_(0),
+      __intbuf_(nullptr),
       __ibs_(0),
-      __file_(0),
+      __file_(nullptr),
       __cv_(nullptr),
       __st_(),
       __st_last_(),
       __om_(0),
       __cm_(0),
       __owns_eb_(false),
       __owns_ib_(false),
       __always_noconv_(false)
 {
     if (has_facet<codecvt<char_type, char, state_type> >(this->getloc()))
     {
         __cv_ = &use_facet<codecvt<char_type, char, state_type> >(this->getloc());
         __always_noconv_ = __cv_->always_noconv();
     }
-    setbuf(0, 4096);
+    setbuf(nullptr, 4096);
 }
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>::basic_filebuf(basic_filebuf&& __rhs)
     : basic_streambuf<_CharT, _Traits>(__rhs)
 {
else if (__rhs.eback())
         if (__rhs.eback() == __rhs.__intbuf_)
             this->setg(__intbuf_, __intbuf_ + (__rhs.gptr() - __rhs.eback()),
                                   __intbuf_ + (__rhs.egptr() - __rhs.eback()));
         else
             this->setg((char_type*)__extbuf_,
                        (char_type*)__extbuf_ + (__rhs.gptr() - __rhs.eback()),
                        (char_type*)__extbuf_ + (__rhs.egptr() - __rhs.eback()));
     }
-    __rhs.__extbuf_ = 0;
-    __rhs.__extbufnext_ = 0;
-    __rhs.__extbufend_ = 0;
+    __rhs.__extbuf_ = nullptr;
+    __rhs.__extbufnext_ = nullptr;
+    __rhs.__extbufend_ = nullptr;
     __rhs.__ebs_ = 0;
     __rhs.__intbuf_ = 0;
     __rhs.__ibs_ = 0;
-    __rhs.__file_ = 0;
+    __rhs.__file_ = nullptr;
     __rhs.__st_ = state_type();
     __rhs.__st_last_ = state_type();
     __rhs.__om_ = 0;
     __rhs.__cm_ = 0;
     __rhs.__owns_eb_ = false;
     __rhs.__owns_ib_ = false;
     __rhs.setg(0, 0, 0);
     __rhs.setp(0, 0);
swap(basic_filebuf<_CharT, _Traits>& __x, basic_filebuf<_CharT, _Traits>& __y)
     __x.swap(__y);
 }
 
 template <class _CharT, class _Traits>
 inline
 bool
 basic_filebuf<_CharT, _Traits>::is_open() const
 {
-    return __file_ != 0;
+    return __file_ != nullptr;
 }
 
 template <class _CharT, class _Traits>
 const char* basic_filebuf<_CharT, _Traits>::__make_mdstring(
     ios_base::openmode __mode) _NOEXCEPT {
   switch (__mode & ~ios_base::ate) {
   case ios_base::out:
   case ios_base::out | ios_base::trunc:
const char* basic_filebuf<_CharT, _Traits>::__make_mdstring(
   _LIBCPP_UNREACHABLE();
 }
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode)
 {
-    basic_filebuf<_CharT, _Traits>* __rt = 0;
-    if (__file_ == 0)
+    basic_filebuf<_CharT, _Traits>* __rt = nullptr;
+    if (__file_ == nullptr)
     {
       if (const char* __mdstr = __make_mdstring(__mode)) {
         __rt = this;
         __file_ = fopen(__s, __mdstr);
         if (__file_) {
           __om_ = __mode;
           if (__mode & ios_base::ate) {
             if (fseek(__file_, 0, SEEK_END)) {
               fclose(__file_);
-              __file_ = 0;
-              __rt = 0;
+              __file_ = nullptr;
+              __rt = nullptr;
             }
           }
         } else
-          __rt = 0;
+          __rt = nullptr;
       }
     }
     return __rt;
 }
 
 template <class _CharT, class _Traits>
 _LIBCPP_INLINE_VISIBILITY basic_filebuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::__open(int __fd, ios_base::openmode __mode) {
-  basic_filebuf<_CharT, _Traits>* __rt = 0;
-  if (__file_ == 0) {
+  basic_filebuf<_CharT, _Traits>* __rt = nullptr;
+  if (__file_ == nullptr) {
     if (const char* __mdstr = __make_mdstring(__mode)) {
       __rt = this;
       __file_ = fdopen(__fd, __mdstr);
       if (__file_) {
         __om_ = __mode;
         if (__mode & ios_base::ate) {
           if (fseek(__file_, 0, SEEK_END)) {
             fclose(__file_);
-            __file_ = 0;
-            __rt = 0;
+            __file_ = nullptr;
+            __rt = nullptr;
           }
         }
       } else
-        __rt = 0;
+        __rt = nullptr;
     }
   }
   return __rt;
 }
 
 #ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
 // This is basically the same as the char* overload except that it uses _wfopen
 // and long mode strings.
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::open(const wchar_t* __s, ios_base::openmode __mode)
 {
-    basic_filebuf<_CharT, _Traits>* __rt = 0;
-    if (__file_ == 0)
+    basic_filebuf<_CharT, _Traits>* __rt = nullptr;
+    if (__file_ == nullptr)
     {
         __rt = this;
         const wchar_t* __mdstr;
         switch (__mode & ~ios_base::ate)
         {
         case ios_base::out:
         case ios_base::out | ios_base::trunc:
             __mdstr = L"w";
if (__file_ == nullptr)
         case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
             __mdstr = L"w+b";
             break;
         case ios_base::in | ios_base::out | ios_base::app | ios_base::binary:
         case ios_base::in | ios_base::app | ios_base::binary:
             __mdstr = L"a+b";
             break;
         default:
-            __rt = 0;
+            __rt = nullptr;
             break;
         }
         if (__rt)
         {
             __file_ = _wfopen(__s, __mdstr);
             if (__file_)
             {
                 __om_ = __mode;
                 if (__mode & ios_base::ate)
                 {
                     if (fseek(__file_, 0, SEEK_END))
                     {
                         fclose(__file_);
-                        __file_ = 0;
-                        __rt = 0;
+                        __file_ = nullptr;
+                        __rt = nullptr;
                     }
                 }
             }
             else
-                __rt = 0;
+                __rt = nullptr;
         }
     }
     return __rt;
 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 basic_filebuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mode)
 {
     return open(__s.c_str(), __mode);
 }
 #endif
 
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::close()
 {
-    basic_filebuf<_CharT, _Traits>* __rt = 0;
+    basic_filebuf<_CharT, _Traits>* __rt = nullptr;
     if (__file_)
     {
         __rt = this;
         unique_ptr<FILE, int(*)(FILE*)> __h(__file_, fclose);
         if (sync())
-            __rt = 0;
+            __rt = nullptr;
         if (fclose(__h.release()) == 0)
-            __file_ = 0;
+            __file_ = nullptr;
         else
-            __rt = 0;
+            __rt = nullptr;
         setbuf(0, 0);
     }
     return __rt;
 }
 
 template <class _CharT, class _Traits>
 typename basic_filebuf<_CharT, _Traits>::int_type
 basic_filebuf<_CharT, _Traits>::underflow()
 {
-    if (__file_ == 0)
+    if (__file_ == nullptr)
         return traits_type::eof();
     bool __initial = __read_mode();
     char_type __1buf;
-    if (this->gptr() == 0)
+    if (this->gptr() == nullptr)
         this->setg(&__1buf, &__1buf+1, &__1buf+1);
     const size_t __unget_sz = __initial ? 0 : min<size_t>((this->egptr() - this->eback()) / 2, 4);
     int_type __c = traits_type::eof();
     if (this->gptr() == this->egptr())
     {
         memmove(this->eback(), this->egptr() - __unget_sz, __unget_sz * sizeof(char_type));
         if (__always_noconv_)
         {
if (this->gptr() == this->egptr())
                     __c = traits_type::to_int_type(*this->gptr());
                 }
             }
         }
     }
     else
         __c = traits_type::to_int_type(*this->gptr());
     if (this->eback() == &__1buf)
-        this->setg(0, 0, 0);
+        this->setg(nullptr, nullptr, nullptr);
     return __c;
 }
 
 template <class _CharT, class _Traits>
 typename basic_filebuf<_CharT, _Traits>::int_type
 basic_filebuf<_CharT, _Traits>::pbackfail(int_type __c)
 {
     if (__file_ && this->eback() < this->gptr())
basic_filebuf<_CharT, _Traits>::pbackfail(int_type __c)
     }
     return traits_type::eof();
 }
 
 template <class _CharT, class _Traits>
 typename basic_filebuf<_CharT, _Traits>::int_type
 basic_filebuf<_CharT, _Traits>::overflow(int_type __c)
 {
-    if (__file_ == 0)
+    if (__file_ == nullptr)
         return traits_type::eof();
     __write_mode();
     char_type __1buf;
     char_type* __pb_save = this->pbase();
     char_type* __epb_save = this->epptr();
     if (!traits_type::eq_int_type(__c, traits_type::eof()))
     {
-        if (this->pptr() == 0)
+        if (this->pptr() == nullptr)
             this->setp(&__1buf, &__1buf+1);
         *this->pptr() = traits_type::to_char_type(__c);
         this->pbump(1);
     }
     if (this->pptr() != this->pbase())
     {
         if (__always_noconv_)
         {
basic_filebuf<_CharT, _Traits>::overflow(int_type __c)
     }
     return traits_type::not_eof(__c);
 }
 
 template <class _CharT, class _Traits>
 basic_streambuf<_CharT, _Traits>*
 basic_filebuf<_CharT, _Traits>::setbuf(char_type* __s, streamsize __n)
 {
-    this->setg(0, 0, 0);
-    this->setp(0, 0);
+    this->setg(nullptr, nullptr, nullptr);
+    this->setp(nullptr, nullptr);
     if (__owns_eb_)
         delete [] __extbuf_;
     if (__owns_ib_)
         delete [] __intbuf_;
     __ebs_ = __n;
     if (__ebs_ > sizeof(__extbuf_min_))
     {
         if (__always_noconv_ && __s)
if (!__always_noconv_)
         {
             __intbuf_ = new char_type[__ibs_];
             __owns_ib_ = true;
         }
     }
     else
     {
         __ibs_ = 0;
-        __intbuf_ = 0;
+        __intbuf_ = nullptr;
         __owns_ib_ = false;
     }
     return this;
 }
 
 template <class _CharT, class _Traits>
 typename basic_filebuf<_CharT, _Traits>::pos_type
 basic_filebuf<_CharT, _Traits>::seekoff(off_type __off, ios_base::seekdir __way,
                                         ios_base::openmode)
 {
     if (!__cv_)
         __throw_bad_cast();
 
     int __width = __cv_->encoding();
-    if (__file_ == 0 || (__width <= 0 && __off != 0) || sync())
+    if (__file_ == nullptr || (__width <= 0 && __off != 0) || sync())
         return pos_type(off_type(-1));
     // __width > 0 || __off == 0
     int __whence;
     switch (__way)
     {
     case ios_base::beg:
         __whence = SEEK_SET;
         break;
#endif
     __r.state(__st_);
     return __r;
 }
 
 template <class _CharT, class _Traits>
 typename basic_filebuf<_CharT, _Traits>::pos_type
 basic_filebuf<_CharT, _Traits>::seekpos(pos_type __sp, ios_base::openmode)
 {
-    if (__file_ == 0 || sync())
+    if (__file_ == nullptr || sync())
         return pos_type(off_type(-1));
 #if defined(_LIBCPP_HAS_NO_OFF_T_FUNCTIONS)
     if (fseek(__file_, __sp, SEEK_SET))
         return pos_type(off_type(-1));
 #else
     if (fseeko(__file_, __sp, SEEK_SET))
         return pos_type(off_type(-1));
 #endif
     __st_ = __sp.state();
     return __sp;
 }
 
 template <class _CharT, class _Traits>
 int
 basic_filebuf<_CharT, _Traits>::sync()
 {
-    if (__file_ == 0)
+    if (__file_ == nullptr)
         return 0;
     if (!__cv_)
         __throw_bad_cast();
 
     if (__cm_ & ios_base::out)
     {
         if (this->pptr() != this->pbase())
             if (overflow() == traits_type::eof())
#if defined(_LIBCPP_HAS_NO_OFF_T_FUNCTIONS)
             return -1;
 #else
         if (fseeko(__file_, -__c, SEEK_CUR))
             return -1;
 #endif
         if (__update_st)
             __st_ = __state;
         __extbufnext_ = __extbufend_ = __extbuf_;
-        this->setg(0, 0, 0);
+        this->setg(nullptr, nullptr, nullptr);
         __cm_ = 0;
     }
     return 0;
 }
 
 template <class _CharT, class _Traits>
 void
 basic_filebuf<_CharT, _Traits>::imbue(const locale& __loc)
 {
     sync();
     __cv_ = &use_facet<codecvt<char_type, char, state_type> >(__loc);
     bool __old_anc = __always_noconv_;
     __always_noconv_ = __cv_->always_noconv();
     if (__old_anc != __always_noconv_)
     {
-        this->setg(0, 0, 0);
-        this->setp(0, 0);
+        this->setg(nullptr, nullptr, nullptr);
+        this->setp(nullptr, nullptr);
         // invariant, char_type is char, else we couldn't get here
         if (__always_noconv_)  // need to dump __intbuf_
         {
             if (__owns_eb_)
                 delete [] __extbuf_;
             __owns_eb_ = __owns_ib_;
             __ebs_ = __ibs_;
             __extbuf_ = (char*)__intbuf_;
             __ibs_ = 0;
-            __intbuf_ = 0;
+            __intbuf_ = nullptr;
             __owns_ib_ = false;
         }
         else  // need to obtain an __intbuf_.
         {     // If __extbuf_ is user-supplied, use it, else new __intbuf_
             if (!__owns_eb_ && __extbuf_ != __extbuf_min_)
             {
                 __ibs_ = __ebs_;
                 __intbuf_ = (char_type*)__extbuf_;

 }
 
 template <class _CharT, class _Traits>
 bool
 basic_filebuf<_CharT, _Traits>::__read_mode()
 {
     if (!(__cm_ & ios_base::in))
     {
-        this->setp(0, 0);
+        this->setp(nullptr, nullptr);
         if (__always_noconv_)
             this->setg((char_type*)__extbuf_,
                        (char_type*)__extbuf_ + __ebs_,
                        (char_type*)__extbuf_ + __ebs_);
         else
             this->setg(__intbuf_, __intbuf_ + __ibs_, __intbuf_ + __ibs_);
         __cm_ = ios_base::in;
         return true;
     }
     return false;
 }
 
 template <class _CharT, class _Traits>
 void
 basic_filebuf<_CharT, _Traits>::__write_mode()
 {
     if (!(__cm_ & ios_base::out))
     {
-        this->setg(0, 0, 0);
+        this->setg(nullptr, nullptr, nullptr);
         if (__ebs_ > sizeof(__extbuf_min_))
         {
             if (__always_noconv_)
                 this->setp((char_type*)__extbuf_,
                            (char_type*)__extbuf_ + (__ebs_ - 1));
             else
                 this->setp(__intbuf_, __intbuf_ + (__ibs_ - 1));
         }
         else
-            this->setp(0, 0);
+            this->setp(nullptr, nullptr);
         __cm_ = ios_base::out;
     }
 }
 
 // basic_ifstream
 
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS basic_ifstream

 }
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 template <class _CharT, class _Traits>
 inline
 basic_ifstream<_CharT, _Traits>::basic_ifstream(const char* __s, ios_base::openmode __mode)
     : basic_istream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::in) == 0)
+    if (__sb_.open(__s, __mode | ios_base::in) == nullptr)
         this->setstate(ios_base::failbit);
 }
 
 #ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
 template <class _CharT, class _Traits>
 inline
 basic_ifstream<_CharT, _Traits>::basic_ifstream(const wchar_t* __s, ios_base::openmode __mode)
     : basic_istream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::in) == 0)
+    if (__sb_.open(__s, __mode | ios_base::in) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 basic_ifstream<_CharT, _Traits>::basic_ifstream(const string& __s, ios_base::openmode __mode)
     : basic_istream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::in) == 0)
+    if (__sb_.open(__s, __mode | ios_base::in) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline

 }
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 template <class _CharT, class _Traits>
 inline
 basic_ofstream<_CharT, _Traits>::basic_ofstream(const char* __s, ios_base::openmode __mode)
     : basic_ostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::out) == 0)
+    if (__sb_.open(__s, __mode | ios_base::out) == nullptr)
         this->setstate(ios_base::failbit);
 }
 
 #ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
 template <class _CharT, class _Traits>
 inline
 basic_ofstream<_CharT, _Traits>::basic_ofstream(const wchar_t* __s, ios_base::openmode __mode)
     : basic_ostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::out) == 0)
+    if (__sb_.open(__s, __mode | ios_base::out) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 basic_ofstream<_CharT, _Traits>::basic_ofstream(const string& __s, ios_base::openmode __mode)
     : basic_ostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode | ios_base::out) == 0)
+    if (__sb_.open(__s, __mode | ios_base::out) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline

 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 void
 basic_ofstream<_CharT, _Traits>::close()
 {
-    if (__sb_.close() == 0)
+    if (__sb_.close() == nullptr)
         this->setstate(ios_base::failbit);
 }
 
 // basic_fstream
 
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS basic_fstream
     : public basic_iostream<_CharT, _Traits>

 }
 
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 template <class _CharT, class _Traits>
 inline
 basic_fstream<_CharT, _Traits>::basic_fstream(const char* __s, ios_base::openmode __mode)
     : basic_iostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode) == 0)
+    if (__sb_.open(__s, __mode) == nullptr)
         this->setstate(ios_base::failbit);
 }
 
 #ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
 template <class _CharT, class _Traits>
 inline
 basic_fstream<_CharT, _Traits>::basic_fstream(const wchar_t* __s, ios_base::openmode __mode)
     : basic_iostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode) == 0)
+    if (__sb_.open(__s, __mode) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 basic_fstream<_CharT, _Traits>::basic_fstream(const string& __s, ios_base::openmode __mode)
     : basic_iostream<char_type, traits_type>(&__sb_)
 {
-    if (__sb_.open(__s, __mode) == 0)
+    if (__sb_.open(__s, __mode) == nullptr)
         this->setstate(ios_base::failbit);
 }
 #endif
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline

 }
 #endif
 
 template <class _CharT, class _Traits>
 inline
 void
 basic_fstream<_CharT, _Traits>::close()
 {
-    if (__sb_.close() == 0)
+    if (__sb_.close() == nullptr)
         this->setstate(ios_base::failbit);
 }
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
 #endif  // _LIBCPP_FSTREAM

include/functional

 #ifndef _LIBCPP_NO_RTTI
 
 template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
 const void*
 __func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target(const type_info& __ti) const _NOEXCEPT
 {
     if (__ti == typeid(_Fp))
         return &__f_.__target();
-    return (const void*)0;
+    return nullptr;
 }
 
 template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
 const std::type_info&
 __func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
 {
     return typeid(_Fp);
 }

include/ios

 }
 
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_ios<_CharT, _Traits>::init(basic_streambuf<char_type, traits_type>* __sb)
 {
     ios_base::init(__sb);
-    __tie_ = 0;
+    __tie_ = nullptr;
     __fill_ = traits_type::eof();
 }
 
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>*
 basic_ios<_CharT, _Traits>::tie() const
 {

 
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_ios<_CharT, _Traits>::move(basic_ios& __rhs)
 {
     ios_base::move(__rhs);
     __tie_ = __rhs.__tie_;
-    __rhs.__tie_ = 0;
+    __rhs.__tie_ = nullptr;
     __fill_ = __rhs.__fill_;
 }
 
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_ios<_CharT, _Traits>::swap(basic_ios& __rhs) _NOEXCEPT
 {

include/istream

basic_istream<_CharT, _Traits>::putback(char_type __c)
     this->clear(__state);
     sentry __sen(*this, true);
     if (__sen)
     {
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
-            if (this->rdbuf() == 0 || this->rdbuf()->sputbackc(__c) == traits_type::eof())
+            if (this->rdbuf() == nullptr || this->rdbuf()->sputbackc(__c) == traits_type::eof())
                 __state |= ios_base::badbit;
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
             __state |= ios_base::badbit;
             this->__setstate_nothrow(__state);
             if (this->exceptions() & ios_base::badbit)
basic_istream<_CharT, _Traits>::unget()
     this->clear(__state);
     sentry __sen(*this, true);
     if (__sen)
     {
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
-            if (this->rdbuf() == 0 || this->rdbuf()->sungetc() == traits_type::eof())
+            if (this->rdbuf() == nullptr || this->rdbuf()->sungetc() == traits_type::eof())
                 __state |= ios_base::badbit;
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
             __state |= ios_base::badbit;
             this->__setstate_nothrow(__state);
             if (this->exceptions() & ios_base::badbit)
basic_istream<_CharT, _Traits>::sync()
     int __r = 0;
     sentry __sen(*this, true);
     if (__sen)
     {
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
-            if (this->rdbuf() == 0)
+            if (this->rdbuf() == nullptr)
                 return -1;
             if (this->rdbuf()->pubsync() == -1)
             {
                 __state |= ios_base::badbit;
                 return -1;
             }
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }

include/iterator

 
 
 template <class _Tp>
 struct __has_iterator_category
 {
 private:
     struct __two {char __lx; char __lxx;};
     template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::iterator_category* = 0);
+    template <class _Up> static char __test(typename _Up::iterator_category* = nullptr);
 public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
+    static const bool value = sizeof(__test<_Tp>(nullptr)) == 1;
 };
 
 template <class _Iter, bool> struct __iterator_traits_impl {};
 
 template <class _Iter>
 struct __iterator_traits_impl<_Iter, true>
 {
     typedef typename _Iter::difference_type   difference_type;

 public:
     typedef _CharT char_type;
     typedef _Traits traits_type;
     typedef basic_istream<_CharT,_Traits> istream_type;
 private:
     istream_type* __in_stream_;
     _Tp __value_;
 public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istream_iterator() : __in_stream_(0), __value_() {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istream_iterator() : __in_stream_(nullptr), __value_() {}
     _LIBCPP_INLINE_VISIBILITY istream_iterator(istream_type& __s) : __in_stream_(_VSTD::addressof(__s))
         {
             if (!(*__in_stream_ >> __value_))
-                __in_stream_ = 0;
+                __in_stream_ = nullptr;
         }
 
     _LIBCPP_INLINE_VISIBILITY const _Tp& operator*() const {return __value_;}
     _LIBCPP_INLINE_VISIBILITY const _Tp* operator->() const {return _VSTD::addressof((operator*()));}
     _LIBCPP_INLINE_VISIBILITY istream_iterator& operator++()
         {
             if (!(*__in_stream_ >> __value_))
-                __in_stream_ = 0;
+                __in_stream_ = nullptr;
             return *this;
         }
     _LIBCPP_INLINE_VISIBILITY istream_iterator  operator++(int)
         {istream_iterator __t(*this); ++(*this); return __t;}
 
     template <class _Up, class _CharU, class _TraitsU, class _DistanceU>
     friend _LIBCPP_INLINE_VISIBILITY
     bool
public:
     typedef _CharT char_type;
     typedef _Traits traits_type;
     typedef basic_ostream<_CharT,_Traits> ostream_type;
 private:
     ostream_type* __out_stream_;
     const char_type* __delim_;
 public:
     _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s) _NOEXCEPT
-        : __out_stream_(_VSTD::addressof(__s)), __delim_(0) {}
+        : __out_stream_(_VSTD::addressof(__s)), __delim_(nullptr) {}
     _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s, const _CharT* __delimiter) _NOEXCEPT
         : __out_stream_(_VSTD::addressof(__s)), __delim_(__delimiter) {}
     _LIBCPP_INLINE_VISIBILITY ostream_iterator& operator=(const _Tp& __value_)
         {
             *__out_stream_ << __value_;
             if (__delim_)
                 *__out_stream_ << __delim_;
             return *this;
private:
     public:
         _LIBCPP_INLINE_VISIBILITY char_type operator*() const {return __keep_;}
     };
 
     _LIBCPP_INLINE_VISIBILITY
     bool __test_for_eof() const
     {
         if (__sbuf_ && traits_type::eq_int_type(__sbuf_->sgetc(), traits_type::eof()))
-            __sbuf_ = 0;
-        return __sbuf_ == 0;
+            __sbuf_ = nullptr;
+        return __sbuf_ == nullptr;
     }
 public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istreambuf_iterator() _NOEXCEPT : __sbuf_(0) {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR istreambuf_iterator() _NOEXCEPT : __sbuf_(nullptr) {}
     _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(istream_type& __s) _NOEXCEPT
         : __sbuf_(__s.rdbuf()) {}
     _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(streambuf_type* __s) _NOEXCEPT
         : __sbuf_(__s) {}
     _LIBCPP_INLINE_VISIBILITY istreambuf_iterator(const __proxy& __p) _NOEXCEPT
         : __sbuf_(__p.__sbuf_) {}
 
     _LIBCPP_INLINE_VISIBILITY char_type  operator*() const

 public:
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(ostream_type& __s) _NOEXCEPT
         : __sbuf_(__s.rdbuf()) {}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator(streambuf_type* __s) _NOEXCEPT
         : __sbuf_(__s) {}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator=(_CharT __c)
         {
             if (__sbuf_ && traits_type::eq_int_type(__sbuf_->sputc(__c), traits_type::eof()))
-                __sbuf_ = 0;
+                __sbuf_ = nullptr;
             return *this;
         }
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator*()     {return *this;}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator++()    {return *this;}
     _LIBCPP_INLINE_VISIBILITY ostreambuf_iterator& operator++(int) {return *this;}
-    _LIBCPP_INLINE_VISIBILITY bool failed() const _NOEXCEPT {return __sbuf_ == 0;}
+    _LIBCPP_INLINE_VISIBILITY bool failed() const _NOEXCEPT {return __sbuf_ == nullptr;}
 
     template <class _Ch, class _Tr>
     friend
     _LIBCPP_HIDDEN
     ostreambuf_iterator<_Ch, _Tr>
     __pad_and_output(ostreambuf_iterator<_Ch, _Tr> __s,
                      const _Ch* __ob, const _Ch* __op, const _Ch* __oe,
                      ios_base& __iob, _Ch __fl);

 #endif
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         __get_db()->__insert_i(this);
 #endif
     }
     template <class _Up> _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
         __wrap_iter(const __wrap_iter<_Up>& __u,
-            typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = 0) _NOEXCEPT
+            typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = nullptr) _NOEXCEPT
             : __i(__u.base())
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         __get_db()->__iterator_copy(this, &__u);
 #endif
     }
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG

include/locale

 {
     typedef typename iterator_traits<_InputIterator>::value_type _CharT;
     size_t __nkw = static_cast<size_t>(_VSTD::distance(__kb, __ke));
     const unsigned char __doesnt_match = '\0';
     const unsigned char __might_match = '\1';
     const unsigned char __does_match = '\2';
     unsigned char __statbuf[100];
     unsigned char* __status = __statbuf;
-    unique_ptr<unsigned char, void(*)(void*)> __stat_hold(0, free);
+    unique_ptr<unsigned char, void(*)(void*)> __stat_hold(nullptr, free);
     if (__nkw > sizeof(__statbuf))
     {
         __status = (unsigned char*)malloc(__nkw);
-        if (__status == 0)
+        if (__status == nullptr)
             __throw_bad_alloc();
         __stat_hold.reset(__status);
     }
     size_t __n_might_match = __nkw;  // At this point, any keyword might match
     size_t __n_does_match = 0;       // but none of them definitely do
     // Initialize all statuses to __might_match, except for "" keywords are __does_match
     unsigned char* __st = __status;
     for (_ForwardIterator __ky = __kb; __ky != __ke; ++__ky, (void) ++__st)
num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     char __nar[__nbuf];
     char* __nb = __nar;
     int __nc;
     if (__specify_precision)
         __nc = __libcpp_snprintf_l(__nb, __nbuf, _LIBCPP_GET_C_LOCALE, __fmt,
                                    (int)__iob.precision(), __v);
     else
         __nc = __libcpp_snprintf_l(__nb, __nbuf, _LIBCPP_GET_C_LOCALE, __fmt, __v);
-    unique_ptr<char, void(*)(void*)> __nbh(0, free);
+    unique_ptr<char, void(*)(void*)> __nbh(nullptr, free);
     if (__nc > static_cast<int>(__nbuf-1))
     {
         if (__specify_precision)
             __nc = __libcpp_asprintf_l(&__nb, _LIBCPP_GET_C_LOCALE, __fmt, (int)__iob.precision(), __v);
         else
             __nc = __libcpp_asprintf_l(&__nb, _LIBCPP_GET_C_LOCALE, __fmt, __v);
-        if (__nb == 0)
+        if (__nb == nullptr)
             __throw_bad_alloc();
         __nbh.reset(__nb);
     }
     char* __ne = __nb + __nc;
     char* __np = this->__identify_padding(__nb, __ne, __iob);
     // Stage 2 - Widen __nar while adding thousands separators
     char_type __o[2*(__nbuf-1) - 1];
     char_type* __ob = __o;
num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     char __nar[__nbuf];
     char* __nb = __nar;
     int __nc;
     if (__specify_precision)
         __nc = __libcpp_snprintf_l(__nb, __nbuf, _LIBCPP_GET_C_LOCALE, __fmt,
                                    (int)__iob.precision(), __v);
     else
         __nc = __libcpp_snprintf_l(__nb, __nbuf, _LIBCPP_GET_C_LOCALE, __fmt, __v);
-    unique_ptr<char, void(*)(void*)> __nbh(0, free);
+    unique_ptr<char, void(*)(void*)> __nbh(nullptr, free);
     if (__nc > static_cast<int>(__nbuf-1))
     {
         if (__specify_precision)
             __nc = __libcpp_asprintf_l(&__nb, _LIBCPP_GET_C_LOCALE, __fmt, (int)__iob.precision(), __v);
         else
             __nc = __libcpp_asprintf_l(&__nb, _LIBCPP_GET_C_LOCALE, __fmt, __v);
-        if (__nb == 0)
+        if (__nb == nullptr)
             __throw_bad_alloc();
         __nbh.reset(__nb);
     }
     char* __ne = __nb + __nc;
     char* __np = this->__identify_padding(__nb, __ne, __iob);
     // Stage 2 - Widen __nar while adding thousands separators
     char_type __o[2*(__nbuf-1) - 1];
     char_type* __ob = __o;
money_get<_CharT, _InputIterator>::do_get(iter_type __b, iter_type __e,
     if (__do_get(__b, __e, __intl, __loc, __iob.flags(), __err, __neg, __ct,
                  __wb, __wn, __we))
     {
         const char __src[] = "0123456789";
         char_type __atoms[sizeof(__src)-1];
         __ct.widen(__src, __src + (sizeof(__src)-1), __atoms);
         char __nbuf[__bz];
         char* __nc = __nbuf;
-        unique_ptr<char, void(*)(void*)> __h(0, free);
+        unique_ptr<char, void(*)(void*)> __h(nullptr, free);
         if (__wn - __wb.get() > __bz-2)
         {
             __h.reset((char*)malloc(static_cast<size_t>(__wn - __wb.get() + 2)));
-            if (__h.get() == 0)
+            if (__h.get() == nullptr)
                 __throw_bad_alloc();
             __nc = __h.get();
         }
         if (__neg)
             *__nc++ = '-';
         for (const char_type* __w = __wb.get(); __w < __wn; ++__w, ++__nc)
             *__nc = __src[find(__atoms, _VSTD::end(__atoms), *__w) - __atoms];
         *__nc = char();

 {
     // convert to char
     const size_t __bs = 100;
     char __buf[__bs];
     char* __bb = __buf;
     char_type __digits[__bs];
     char_type* __db = __digits;
     size_t __n = static_cast<size_t>(snprintf(__bb, __bs, "%.0Lf", __units));
-    unique_ptr<char, void(*)(void*)> __hn(0, free);
+    unique_ptr<char, void(*)(void*)> __hn(nullptr, free);
     unique_ptr<char_type, void(*)(void*)> __hd(0, free);
     // secure memory for digit storage
     if (__n > __bs-1)
     {
         __n = static_cast<size_t>(__libcpp_asprintf_l(&__bb, _LIBCPP_GET_C_LOCALE, "%.0Lf", __units));
-        if (__bb == 0)
+        if (__bb == nullptr)
             __throw_bad_alloc();
         __hn.reset(__bb);
         __hd.reset((char_type*)malloc(__n * sizeof(char_type)));
         if (__hd == nullptr)
             __throw_bad_alloc();
         __db = __hd.get();
     }
     // gather info
private:
     ios_base::openmode __cm_;
     bool __owns_eb_;
     bool __owns_ib_;
     bool __always_noconv_;
 
     wbuffer_convert(const wbuffer_convert&);
     wbuffer_convert& operator=(const wbuffer_convert&);
 public:
-    _LIBCPP_EXPLICIT_AFTER_CXX11 wbuffer_convert(streambuf* __bytebuf = 0,
+    _LIBCPP_EXPLICIT_AFTER_CXX11 wbuffer_convert(streambuf* __bytebuf = nullptr,
             _Codecvt* __pcvt = new _Codecvt, state_type __state = state_type());
     ~wbuffer_convert();
 
     _LIBCPP_INLINE_VISIBILITY
     streambuf* rdbuf() const {return __bufptr_;}
     _LIBCPP_INLINE_VISIBILITY
     streambuf* rdbuf(streambuf* __bytebuf)
     {
private:
     bool __read_mode();
     void __write_mode();
     wbuffer_convert* __close();
 };
 
 template <class _Codecvt, class _Elem, class _Tr>
 wbuffer_convert<_Codecvt, _Elem, _Tr>::
     wbuffer_convert(streambuf* __bytebuf, _Codecvt* __pcvt, state_type __state)
-    : __extbuf_(0),
-      __extbufnext_(0),
-      __extbufend_(0),
+    : __extbuf_(nullptr),
+      __extbufnext_(nullptr),
+      __extbufend_(nullptr),
       __ebs_(0),
       __intbuf_(0),
       __ibs_(0),
       __bufptr_(__bytebuf),
       __cv_(__pcvt),
       __st_(__state),
       __cm_(0),
       __owns_eb_(false),

include/memory

 };
 
 template <class _Tp, class _Up, bool = __has_rebind<_Tp, _Up>::value>
 struct __has_rebind_other
 {
 private:
     struct __two {char __lx; char __lxx;};
     template <class _Xp> static __two __test(...);
     template <class _Xp> static char __test(typename _Xp::template rebind<_Up>::other* = 0);
 public:
     static const bool value = sizeof(__test<_Tp>(0)) == 1;
 };
 
 template <class _Tp, class _Up>
 struct __has_rebind_other<_Tp, _Up, false>
 {
     static const bool value = false;
public:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     allocator(const allocator<_Up>&) _NOEXCEPT {}
 
     _LIBCPP_INLINE_VISIBILITY pointer address(reference __x) const _NOEXCEPT
         {return _VSTD::addressof(__x);}
     _LIBCPP_INLINE_VISIBILITY const_pointer address(const_reference __x) const _NOEXCEPT
         {return _VSTD::addressof(__x);}
     _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
-    pointer allocate(size_type __n, allocator<void>::const_pointer = 0)
+    pointer allocate(size_type __n, allocator<void>::const_pointer = nullptr)
         {
         if (__n > max_size())
             __throw_length_error("allocator<T>::allocate(size_t n)"
                                  " 'n' exceeds maximum supported size");
         return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
         }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) _NOEXCEPT
         {_VSTD::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));}
public:
     allocator() _NOEXCEPT {}
 
     template <class _Up>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     allocator(const allocator<_Up>&) _NOEXCEPT {}
 
     _LIBCPP_INLINE_VISIBILITY const_pointer address(const_reference __x) const _NOEXCEPT
         {return _VSTD::addressof(__x);}
-    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, allocator<void>::const_pointer = 0)
+    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, allocator<void>::const_pointer = nullptr)
     {
         if (__n > max_size())
             __throw_length_error("allocator<const T>::allocate(size_t n)"
                                  " 'n' exceeds maximum supported size");
         return static_cast<pointer>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
     }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type __n) _NOEXCEPT
         {_VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p), __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));}
public:
 
     _LIBCPP_INLINE_VISIBILITY _Tp& operator*() const throw()
         {return *__ptr_;}
     _LIBCPP_INLINE_VISIBILITY _Tp* operator->() const throw() {return __ptr_;}
     _LIBCPP_INLINE_VISIBILITY _Tp* get() const throw() {return __ptr_;}
     _LIBCPP_INLINE_VISIBILITY _Tp* release() throw()
     {
         _Tp* __t = __ptr_;
-        __ptr_ = 0;
+        __ptr_ = nullptr;
         return __t;
     }
     _LIBCPP_INLINE_VISIBILITY void reset(_Tp* __p = 0) throw()
     {
         if (__ptr_ != __p)
             delete __ptr_;
         __ptr_ = __p;
     }
private:
     template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
 };
 
 
 template<class _Tp>
 inline
 _LIBCPP_CONSTEXPR
 shared_ptr<_Tp>::shared_ptr() _NOEXCEPT
-    : __ptr_(0),
-      __cntrl_(0)
+    : __ptr_(nullptr),
+      __cntrl_(nullptr)
 {
 }
 
 template<class _Tp>
 inline
 _LIBCPP_CONSTEXPR
 shared_ptr<_Tp>::shared_ptr(nullptr_t) _NOEXCEPT
-    : __ptr_(0),
-      __cntrl_(0)
+    : __ptr_(nullptr),
+      __cntrl_(nullptr)
 {
 }
 
 template<class _Tp>
 template<class _Yp>
 shared_ptr<_Tp>::shared_ptr(_Yp* __p,
                             typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
     : __ptr_(__p)
catch (...)
         throw;
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 template<class _Tp>
 template<class _Dp>
 shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d)
-    : __ptr_(0)
+    : __ptr_(nullptr)
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         typedef typename __shared_ptr_default_allocator<_Tp>::type _AllocT;
         typedef __shared_ptr_pointer<nullptr_t, _Dp, _AllocT > _CntrlBlk;
         __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
catch (...)
         throw;
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 template<class _Tp>
 template<class _Dp, class _Alloc>
 shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d, _Alloc __a)
-    : __ptr_(0)
+    : __ptr_(nullptr)
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         typedef __shared_ptr_pointer<nullptr_t, _Dp, _Alloc> _CntrlBlk;
         typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
         typedef __allocator_destructor<_A2> _D2;

 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template<class _Tp>
 inline
 shared_ptr<_Tp>::shared_ptr(shared_ptr&& __r) _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
-    __r.__ptr_ = 0;
-    __r.__cntrl_ = 0;
+    __r.__ptr_ = nullptr;
+    __r.__cntrl_ = nullptr;
 }
 
 template<class _Tp>
 template<class _Yp>
 inline
 shared_ptr<_Tp>::shared_ptr(shared_ptr<_Yp>&& __r,
                             typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
-    __r.__ptr_ = 0;
-    __r.__cntrl_ = 0;
+    __r.__ptr_ = nullptr;
+    __r.__cntrl_ = nullptr;
 }
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template<class _Tp>
 template<class _Yp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
     template <class _Up> friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
 };
 
 template<class _Tp>
 inline
 _LIBCPP_CONSTEXPR
 weak_ptr<_Tp>::weak_ptr() _NOEXCEPT
-    : __ptr_(0),
-      __cntrl_(0)
+    : __ptr_(nullptr),
+      __cntrl_(nullptr)
 {
 }
 
 template<class _Tp>
 inline
 weak_ptr<_Tp>::weak_ptr(weak_ptr const& __r) _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)

 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template<class _Tp>
 inline
 weak_ptr<_Tp>::weak_ptr(weak_ptr&& __r) _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
-    __r.__ptr_ = 0;
-    __r.__cntrl_ = 0;
+    __r.__ptr_ = nullptr;
+    __r.__cntrl_ = nullptr;
 }
 
 template<class _Tp>
 template<class _Yp>
 inline
 weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp>&& __r,
                         typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
 {
-    __r.__ptr_ = 0;
-    __r.__cntrl_ = 0;
+    __r.__ptr_ = nullptr;
+    __r.__cntrl_ = nullptr;
 }
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template<class _Tp>
 weak_ptr<_Tp>::~weak_ptr()
 {
     if (__cntrl_)

include/regex

public:
     static const regex_constants::syntax_option_type awk = regex_constants::awk;
     static const regex_constants::syntax_option_type grep = regex_constants::grep;
     static const regex_constants::syntax_option_type egrep = regex_constants::egrep;
 
     // construct/copy/destroy:
     _LIBCPP_INLINE_VISIBILITY
     basic_regex()
         : __flags_(regex_constants::ECMAScript), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {}
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_regex(const value_type* __p, flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {
         if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
         __parse(__p, __p + __traits_.length(__p));
         }
 
     _LIBCPP_INLINE_VISIBILITY
     basic_regex(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {
         if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
         __parse(__p, __p + __len);
         }
 
 //     basic_regex(const basic_regex&) = default;
 //     basic_regex(basic_regex&&) = default;
     template <class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY
         explicit basic_regex(const basic_string<value_type, _ST, _SA>& __p,
                              flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {
         if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
         __parse(__p.begin(), __p.end());
         }
 
     template <class _ForwardIterator>
         _LIBCPP_INLINE_VISIBILITY
         basic_regex(_ForwardIterator __first, _ForwardIterator __last,
                     flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {
         if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
         __parse(__first, __last);
         }
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_regex(initializer_list<value_type> __il,
                 flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
-          __end_(0)
+          __end_(nullptr)
         {
         if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
         __parse(__il.begin(), __il.end());
         }
 #endif  // _LIBCPP_CXX03_LANG
 
 //    ~basic_regex() = default;
 

include/sstream

virtual pos_type seekoff(off_type __off, ios_base::seekdir __way,
                              ios_base::openmode __wch = ios_base::in | ios_base::out);
     inline _LIBCPP_INLINE_VISIBILITY
     virtual pos_type seekpos(pos_type __sp,
                              ios_base::openmode __wch = ios_base::in | ios_base::out);
 };
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(ios_base::openmode __wch)
-    : __hm_(0),
+    : __hm_(nullptr),
       __mode_(__wch)
 {
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(const string_type& __s,
                              ios_base::openmode __wch)
     : __str_(__s.get_allocator()),
-      __hm_(0),
+      __hm_(nullptr),
       __mode_(__wch)
 {
     str(__s);
 }
 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
basic_stringbuf<_CharT, _Traits, _Allocator>::str() const
     return string_type(__str_.get_allocator());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 void
 basic_stringbuf<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 {
     __str_ = __s;
-    __hm_ = 0;
+    __hm_ = nullptr;
     if (__mode_ & ios_base::in)
     {
         __hm_ = const_cast<char_type*>(__str_.data()) + __str_.size();
         this->setg(const_cast<char_type*>(__str_.data()),
                    const_cast<char_type*>(__str_.data()),
                    __hm_);
     }
     if (__mode_ & ios_base::out)
basic_stringbuf<_CharT, _Traits, _Allocator>::seekoff(off_type __off,
     default:
         return pos_type(-1);
     }
     __noff += __off;
     if (__noff < 0 || __hm < __noff)
         return pos_type(-1);
     if (__noff != 0)
     {
-        if ((__wch & ios_base::in) && this->gptr() == 0)
+        if ((__wch & ios_base::in) && this->gptr() == nullptr)
             return pos_type(-1);
-        if ((__wch & ios_base::out) && this->pptr() == 0)
+        if ((__wch & ios_base::out) && this->pptr() == nullptr)
             return pos_type(-1);
     }
     if (__wch & ios_base::in)
         this->setg(this->eback(), this->eback() + __noff, __hm_);
     if (__wch & ios_base::out)
     {
         this->setp(this->pbase(), this->epptr());
         this->pbump(__noff);

include/streambuf

 
 template <class _CharT, class _Traits>
 basic_streambuf<_CharT, _Traits>::~basic_streambuf()
 {
 }
 
 template <class _CharT, class _Traits>
 basic_streambuf<_CharT, _Traits>::basic_streambuf()
-    : __binp_(0),
-      __ninp_(0),
-      __einp_(0),
-      __bout_(0),
-      __nout_(0),
-      __eout_(0)
+    : __binp_(nullptr),
+      __ninp_(nullptr),
+      __einp_(nullptr),
+      __bout_(nullptr),
+      __nout_(nullptr),
+      __eout_(nullptr)
 {
 }
 
 template <class _CharT, class _Traits>
 basic_streambuf<_CharT, _Traits>::basic_streambuf(const basic_streambuf& __sb)
     : __loc_(__sb.__loc_),
       __binp_(__sb.__binp_),
       __ninp_(__sb.__ninp_),

include/string

 template<class charT, class traits, class Allocator, class Predicate>
 void erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred); // C++20
 
 typedef basic_string<char>    string;
 typedef basic_string<wchar_t> wstring;
 typedef basic_string<char16_t> u16string;
 typedef basic_string<char32_t> u32string;
 
-int                stoi  (const string& str, size_t* idx = 0, int base = 10);
-long               stol  (const string& str, size_t* idx = 0, int base = 10);
-unsigned long      stoul (const string& str, size_t* idx = 0, int base = 10);
-long long          stoll (const string& str, size_t* idx = 0, int base = 10);
-unsigned long long stoull(const string& str, size_t* idx = 0, int base = 10);
-
-float       stof (const string& str, size_t* idx = 0);
-double      stod (const string& str, size_t* idx = 0);
-long double stold(const string& str, size_t* idx = 0);
+int                stoi  (const string& str, size_t* idx = nullptr, int base = 10);
+long               stol  (const string& str, size_t* idx = nullptr, int base = 10);
+unsigned long      stoul (const string& str, size_t* idx = nullptr, int base = 10);
+long long          stoll (const string& str, size_t* idx = nullptr, int base = 10);
+unsigned long long stoull(const string& str, size_t* idx = nullptr, int base = 10);
+
+float       stof (const string& str, size_t* idx = nullptr);
+double      stod (const string& str, size_t* idx = nullptr);
+long double stold(const string& str, size_t* idx = nullptr);
 
 string to_string(int val);
 string to_string(unsigned val);
 string to_string(long val);
 string to_string(unsigned long val);
 string to_string(long long val);
 string to_string(unsigned long long val);
 string to_string(float val);
 string to_string(double val);
 string to_string(long double val);
 
-int                stoi  (const wstring& str, size_t* idx = 0, int base = 10);
-long               stol  (const wstring& str, size_t* idx = 0, int base = 10);
-unsigned long      stoul (const wstring& str, size_t* idx = 0, int base = 10);
-long long          stoll (const wstring& str, size_t* idx = 0, int base = 10);
-unsigned long long stoull(const wstring& str, size_t* idx = 0, int base = 10);
-
-float       stof (const wstring& str, size_t* idx = 0);
-double      stod (const wstring& str, size_t* idx = 0);
-long double stold(const wstring& str, size_t* idx = 0);
+int                stoi  (const wstring& str, size_t* idx = nullptr, int base = 10);
+long               stol  (const wstring& str, size_t* idx = nullptr, int base = 10);
+unsigned long      stoul (const wstring& str, size_t* idx = nullptr, int base = 10);
+long long          stoll (const wstring& str, size_t* idx = nullptr, int base = 10);
+unsigned long long stoull(const wstring& str, size_t* idx = nullptr, int base = 10);
+
+float       stof (const wstring& str, size_t* idx = nullptr);
+double      stod (const wstring& str, size_t* idx = nullptr);
+long double stold(const wstring& str, size_t* idx = nullptr);
 
 wstring to_wstring(int val);
 wstring to_wstring(unsigned val);
 wstring to_wstring(long val);
 wstring to_wstring(unsigned long val);
 wstring to_wstring(long long val);
 wstring to_wstring(unsigned long long val);
 wstring to_wstring(float val);

 inline
 bool
 basic_string<_CharT, _Traits, _Allocator>::__invariants() const
 {
     if (size() > capacity())
         return false;
     if (capacity() < __min_cap - 1)
         return false;
-    if (data() == 0)
+    if (data() == nullptr)
         return false;
     if (data()[size()] != value_type(0))
         return false;
     return true;
 }
 
 // __clear_and_shrink
 

 typedef basic_string<char8_t> u8string;
 #endif
 
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 typedef basic_string<char16_t> u16string;
 typedef basic_string<char32_t> u32string;
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 
-_LIBCPP_FUNC_VIS int                stoi  (const string& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS long               stol  (const string& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS unsigned long      stoul (const string& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS long long          stoll (const string& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS unsigned long long stoull(const string& __str, size_t* __idx = 0, int __base = 10);
-
-_LIBCPP_FUNC_VIS float       stof (const string& __str, size_t* __idx = 0);
-_LIBCPP_FUNC_VIS double      stod (const string& __str, size_t* __idx = 0);
-_LIBCPP_FUNC_VIS long double stold(const string& __str, size_t* __idx = 0);
+_LIBCPP_FUNC_VIS int                stoi  (const string& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS long               stol  (const string& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS unsigned long      stoul (const string& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS long long          stoll (const string& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS unsigned long long stoull(const string& __str, size_t* __idx = nullptr, int __base = 10);
+
+_LIBCPP_FUNC_VIS float       stof (const string& __str, size_t* __idx = nullptr);
+_LIBCPP_FUNC_VIS double      stod (const string& __str, size_t* __idx = nullptr);
+_LIBCPP_FUNC_VIS long double stold(const string& __str, size_t* __idx = nullptr);
 
 _LIBCPP_FUNC_VIS string to_string(int __val);
 _LIBCPP_FUNC_VIS string to_string(unsigned __val);
 _LIBCPP_FUNC_VIS string to_string(long __val);
 _LIBCPP_FUNC_VIS string to_string(unsigned long __val);
 _LIBCPP_FUNC_VIS string to_string(long long __val);
 _LIBCPP_FUNC_VIS string to_string(unsigned long long __val);
 _LIBCPP_FUNC_VIS string to_string(float __val);
 _LIBCPP_FUNC_VIS string to_string(double __val);
 _LIBCPP_FUNC_VIS string to_string(long double __val);
 
-_LIBCPP_FUNC_VIS int                stoi  (const wstring& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS long               stol  (const wstring& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS unsigned long      stoul (const wstring& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS long long          stoll (const wstring& __str, size_t* __idx = 0, int __base = 10);
-_LIBCPP_FUNC_VIS unsigned long long stoull(const wstring& __str, size_t* __idx = 0, int __base = 10);
-
-_LIBCPP_FUNC_VIS float       stof (const wstring& __str, size_t* __idx = 0);
-_LIBCPP_FUNC_VIS double      stod (const wstring& __str, size_t* __idx = 0);
-_LIBCPP_FUNC_VIS long double stold(const wstring& __str, size_t* __idx = 0);
+_LIBCPP_FUNC_VIS int                stoi  (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS long               stol  (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS unsigned long      stoul (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS long long          stoll (const wstring& __str, size_t* __idx = nullptr, int __base = 10);
+_LIBCPP_FUNC_VIS unsigned long long stoull(const wstring& __str, size_t* __idx = nullptr, int __base = 10);
+
+_LIBCPP_FUNC_VIS float       stof (const wstring& __str, size_t* __idx = nullptr);
+_LIBCPP_FUNC_VIS double      stod (const wstring& __str, size_t* __idx = nullptr);
+_LIBCPP_FUNC_VIS long double stold(const wstring& __str, size_t* __idx = nullptr);
 
 _LIBCPP_FUNC_VIS wstring to_wstring(int __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(unsigned __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(long __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(unsigned long __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(long long __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(unsigned long long __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(float __val);

include/strstream

/*
     strstream synopsis
 
 class strstreambuf
     : public basic_streambuf<char>
 {
 public:
     explicit strstreambuf(streamsize alsize_arg = 0);
     strstreambuf(void* (*palloc_arg)(size_t), void (*pfree_arg)(void*));
-    strstreambuf(char* gnext_arg, streamsize n, char* pbeg_arg = 0);
+    strstreambuf(char* gnext_arg, streamsize n, char* pbeg_arg = nullptr);
     strstreambuf(const char* gnext_arg, streamsize n);
 
-    strstreambuf(signed char* gnext_arg, streamsize n, signed char* pbeg_arg = 0);
+    strstreambuf(signed char* gnext_arg, streamsize n, signed char* pbeg_arg = nullptr);
     strstreambuf(const signed char* gnext_arg, streamsize n);
-    strstreambuf(unsigned char* gnext_arg, streamsize n, unsigned char* pbeg_arg = 0);
+    strstreambuf(unsigned char* gnext_arg, streamsize n, unsigned char* pbeg_arg = nullptr);
     strstreambuf(const unsigned char* gnext_arg, streamsize n);
 
     strstreambuf(strstreambuf&& rhs);
     strstreambuf& operator=(strstreambuf&& rhs);
 
     virtual ~strstreambuf();
 
     void swap(strstreambuf& rhs);

 _LIBCPP_BEGIN_NAMESPACE_STD
 
 class _LIBCPP_TYPE_VIS strstreambuf
     : public streambuf
 {
 public:
     explicit strstreambuf(streamsize __alsize = 0);
     strstreambuf(void* (*__palloc)(size_t), void (*__pfree)(void*));
-    strstreambuf(char* __gnext, streamsize __n, char* __pbeg = 0);
+    strstreambuf(char* __gnext, streamsize __n, char* __pbeg = nullptr);
     strstreambuf(const char* __gnext, streamsize __n);
 
-    strstreambuf(signed char* __gnext, streamsize __n, signed char* __pbeg = 0);
+    strstreambuf(signed char* __gnext, streamsize __n, signed char* __pbeg = nullptr);
     strstreambuf(const signed char* __gnext, streamsize __n);
-    strstreambuf(unsigned char* __gnext, streamsize __n, unsigned char* __pbeg = 0);
+    strstreambuf(unsigned char* __gnext, streamsize __n, unsigned char* __pbeg = nullptr);
     strstreambuf(const unsigned char* __gnext, streamsize __n);
 
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     strstreambuf(strstreambuf&& __rhs);
     _LIBCPP_INLINE_VISIBILITY
     strstreambuf& operator=(strstreambuf&& __rhs);
 #endif  // _LIBCPP_CXX03_LANG

include/system_error

public:
 
     _LIBCPP_INLINE_VISIBILITY
     error_condition(int __val, const error_category& __cat) _NOEXCEPT
         : __val_(__val), __cat_(&__cat) {}
 
     template <class _Ep>
         _LIBCPP_INLINE_VISIBILITY
         error_condition(_Ep __e,
-              typename enable_if<is_error_condition_enum<_Ep>::value>::type* = 0
+              typename enable_if<is_error_condition_enum<_Ep>::value>::type* = nullptr
                                                                      ) _NOEXCEPT
             {*this = make_error_condition(__e);}
 
     _LIBCPP_INLINE_VISIBILITY
     void assign(int __val, const error_category& __cat) _NOEXCEPT
     {
         __val_ = __val;
         __cat_ = &__cat;
public:
 
     _LIBCPP_INLINE_VISIBILITY
     error_code(int __val, const error_category& __cat) _NOEXCEPT
         : __val_(__val), __cat_(&__cat) {}
 
     template <class _Ep>
         _LIBCPP_INLINE_VISIBILITY
         error_code(_Ep __e,
-                   typename enable_if<is_error_code_enum<_Ep>::value>::type* = 0
+                   typename enable_if<is_error_code_enum<_Ep>::value>::type* = nullptr
                                                                      ) _NOEXCEPT
             {*this = make_error_code(__e);}
 
     _LIBCPP_INLINE_VISIBILITY
     void assign(int __val, const error_category& __cat) _NOEXCEPT
     {
         __val_ = __val;
         __cat_ = &__cat;

include/valarray

 
 private:
     value_type* __begin_;
     value_type* __end_;
 
 public:
     // construct/destroy:
     _LIBCPP_INLINE_VISIBILITY
-    valarray() : __begin_(0), __end_(0) {}
+    valarray() : __begin_(nullptr), __end_(nullptr) {}
     inline _LIBCPP_HIDE_FROM_ABI_AFTER_V1
     explicit valarray(size_t __n);
     _LIBCPP_INLINE_VISIBILITY
     valarray(const value_type& __x, size_t __n);
     valarray(const value_type* __p, size_t __n);
     valarray(const valarray& __v);
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
__val_expr<_ValExpr>::operator valarray<__val_expr::result_type>() const
     return __r;
 }
 
 // valarray
 
 template <class _Tp>
 inline
 valarray<_Tp>::valarray(size_t __n)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
             _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
#ifndef _LIBCPP_NO_EXCEPTIONS
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 template <class _Tp>
 inline
 valarray<_Tp>::valarray(const value_type& __x, size_t __n)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     resize(__n, __x);
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(const value_type* __p, size_t __n)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
             _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
             for (size_t __n_left = __n; __n_left; ++__end_, ++__p, --__n_left)
                 ::new (__end_) value_type(*__p);
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
             __clear(__n);
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(const valarray& __v)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     if (__v.size())
     {
         __begin_ = __end_ = static_cast<value_type*>(
             _VSTD::__libcpp_allocate(__v.size() * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
valarray<_Tp>::valarray(valarray&& __v) _NOEXCEPT
     : __begin_(__v.__begin_),
       __end_(__v.__end_)
 {
     __v.__begin_ = __v.__end_ = nullptr;
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(initializer_list<value_type> __il)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     const size_t __n = __il.size();
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
 _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try

 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 #endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 valarray<_Tp>::valarray(const slice_array<value_type>& __sa)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     const size_t __n = __sa.__size_;
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
           _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
#ifndef _LIBCPP_NO_EXCEPTIONS
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(const gslice_array<value_type>& __ga)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     const size_t __n = __ga.__1d_.size();
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
            _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
#ifndef _LIBCPP_NO_EXCEPTIONS
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(const mask_array<value_type>& __ma)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     const size_t __n = __ma.__1d_.size();
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
            _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
#ifndef _LIBCPP_NO_EXCEPTIONS
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
     }
 }
 
 template <class _Tp>
 valarray<_Tp>::valarray(const indirect_array<value_type>& __ia)
-    : __begin_(0),
-      __end_(0)
+    : __begin_(nullptr),
+      __end_(nullptr)
 {
     const size_t __n = __ia.__1d_.size();
     if (__n)
     {
         __begin_ = __end_ = static_cast<value_type*>(
            _VSTD::__libcpp_allocate(__n * sizeof(value_type), _LIBCPP_ALIGNOF(value_type)));
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try

src/new.cpp

 
 _LIBCPP_WEAK
 void *
 operator new(std::size_t size) _THROW_BAD_ALLOC
 {
     if (size == 0)
         size = 1;
     void* p;
-    while ((p = ::malloc(size)) == 0)
+    while ((p = ::malloc(size)) == nullptr)
     {
         // If malloc fails and there is a new_handler,
         // call it to try free up memory.
         std::new_handler nh = std::get_new_handler();
         if (nh)
             nh();
         else
 #ifndef _LIBCPP_NO_EXCEPTIONS
             throw std::bad_alloc();
 #else
             break;
 #endif
     }
     return p;
 }
 
 _LIBCPP_WEAK
 void*
 operator new(size_t size, const std::nothrow_t&) _NOEXCEPT
 {
-    void* p = 0;
+    void* p = nullptr;
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         p = ::operator new(size);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)

 {
     return ::operator new(size);
 }
 
 _LIBCPP_WEAK
 void*
 operator new[](size_t size, const std::nothrow_t&) _NOEXCEPT
 {
-    void* p = 0;
+    void* p = nullptr;
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         p = ::operator new[](size);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)
#endif
     }
     return p;
 }
 
 _LIBCPP_WEAK
 void*
 operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
-    void* p = 0;
+    void* p = nullptr;
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         p = ::operator new(size, alignment);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)

 {
     return ::operator new(size, alignment);
 }
 
 _LIBCPP_WEAK
 void*
 operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
-    void* p = 0;
+    void* p = nullptr;
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
         p = ::operator new[](size, alignment);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)