Index: include/string
===================================================================
--- include/string
+++ include/string
@@ -22,7 +22,8 @@
 private:
     stateT st;
 public:
-    fpos(streamoff = streamoff());
+    fpos();
+    fpos(streamoff);
 
     operator streamoff() const;
 
@@ -30,13 +31,12 @@
     void state(stateT);
 
     fpos& operator+=(streamoff);
-    fpos  operator+ (streamoff) const;
+    fpos  operator+ (fpos&) const;
     fpos& operator-=(streamoff);
-    fpos  operator- (streamoff) const;
+    fpos  operator- (fpos&) const;
+    fpos& operator= (fpos);
 };
 
-template <class stateT> streamoff operator-(const fpos<stateT>& x, const fpos<stateT>& y);
-
 template <class stateT> bool operator==(const fpos<stateT>& x, const fpos<stateT>& y);
 template <class stateT> bool operator!=(const fpos<stateT>& x, const fpos<stateT>& y);
 
@@ -540,29 +540,26 @@
     _StateT __st_;
     streamoff __off_;
 public:
-    _LIBCPP_INLINE_VISIBILITY fpos(streamoff __off = streamoff()) : __st_(), __off_(__off) {}
+    _LIBCPP_INLINE_VISIBILITY fpos()                : __st_(), __off_(0    ) {}
+    _LIBCPP_INLINE_VISIBILITY fpos(streamoff __off) : __st_(), __off_(__off) {}
 
     _LIBCPP_INLINE_VISIBILITY operator streamoff() const {return __off_;}
 
     _LIBCPP_INLINE_VISIBILITY _StateT state() const {return __st_;}
     _LIBCPP_INLINE_VISIBILITY void state(_StateT __st) {__st_ = __st;}
 
-    _LIBCPP_INLINE_VISIBILITY fpos& operator+=(streamoff __off) {__off_ += __off; return *this;}
-    _LIBCPP_INLINE_VISIBILITY fpos  operator+ (streamoff __off) const {fpos __t(*this); __t += __off; return __t;}
-    _LIBCPP_INLINE_VISIBILITY fpos& operator-=(streamoff __off) {__off_ -= __off; return *this;}
-    _LIBCPP_INLINE_VISIBILITY fpos  operator- (streamoff __off) const {fpos __t(*this); __t -= __off; return __t;}
+    _LIBCPP_INLINE_VISIBILITY fpos& operator+=(streamoff __off)
+        {__off_ += __off; return *this;}
+    _LIBCPP_INLINE_VISIBILITY fpos operator+ (fpos<_StateT>& __rhs) const
+        {return fpos(__rhs.__off_ + __off_);}
+    _LIBCPP_INLINE_VISIBILITY fpos& operator-=(streamoff __off)
+        {__off_ -= __off; return *this;}
+    _LIBCPP_INLINE_VISIBILITY fpos operator- (fpos<_StateT>& __rhs) const
+        {return fpos(__off_ - __rhs.__off_);}
+    _LIBCPP_INLINE_VISIBILITY fpos& operator= (fpos<_StateT> __rhs)
+        {_VSTD::swap(__rhs.__off_, __off_); return *this;}
 };
 
-template <class _StateT>
-inline _LIBCPP_INLINE_VISIBILITY
-streamoff operator-(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
-    {return streamoff(__x) - streamoff(__y);}
-
-template <class _StateT>
-inline _LIBCPP_INLINE_VISIBILITY
-bool operator==(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
-    {return streamoff(__x) == streamoff(__y);}
-
 template <class _StateT>
 inline _LIBCPP_INLINE_VISIBILITY
 bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
@@ -627,13 +624,13 @@
 #else
 template <class _Iter, bool = __is_forward_iterator<_Iter>::value>
 struct __libcpp_string_gets_noexcept_iterator_impl : public _LIBCPP_BOOL_CONSTANT((
-    noexcept(++(declval<_Iter&>())) && 
-    is_nothrow_assignable<_Iter&, _Iter>::value && 
-    noexcept(declval<_Iter>() == declval<_Iter>()) && 
+    noexcept(++(declval<_Iter&>())) &&
+    is_nothrow_assignable<_Iter&, _Iter>::value &&
+    noexcept(declval<_Iter>() == declval<_Iter>()) &&
     noexcept(*declval<_Iter>())
 )) {};
 
-template <class _Iter> 
+template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator_impl<_Iter, false> : public false_type {};
 #endif
 
@@ -1420,7 +1417,7 @@
     _LIBCPP_INLINE_VISIBILITY bool __invariants() const;
 
     _LIBCPP_INLINE_VISIBILITY void __clear_and_shrink() _NOEXCEPT;
-    
+
     _LIBCPP_INLINE_VISIBILITY
     bool __is_long() const _NOEXCEPT
         {return bool(__r_.first().__s.__size_ & __short_mask);}
@@ -1682,7 +1679,7 @@
   -> basic_string<_CharT, _Traits, _Allocator>;
 #endif
 
-                  
+
 template <class _CharT, class _Traits, class _Allocator>
 inline
 void
@@ -2525,7 +2522,7 @@
             const basic_string __temp (__first, __last, __alloc());
             append(__temp.data(), __temp.size());
         }
-        else 
+        else
         {
             if (__cap - __sz < __n)
                 __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
@@ -3824,7 +3821,7 @@
 
 template<class _CharT, class _Traits, class _Allocator>
 inline
-void 
+void
 basic_string<_CharT, _Traits, _Allocator>::__clear_and_shrink() _NOEXCEPT
 {
     clear();
@@ -3834,7 +3831,7 @@
         __set_long_cap(0);
         __set_short_size(0);
     }
-} 
+}
 
 // operator==
 
@@ -4331,7 +4328,7 @@
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
 
-#if _LIBCPP_STD_VER > 11 
+#if _LIBCPP_STD_VER > 11
 // Literal suffixes for basic_string [basic.string.literals]
 inline namespace literals
 {
Index: test/std/strings/fpos/fpos.pass.cpp
===================================================================
--- /dev/null
+++ test/std/strings/fpos/fpos.pass.cpp
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "test_macros.h"
+
+#include <string>
+#include <cassert>
+
+// string
+// template <class stateT>
+// class fpos
+// {
+//     fpos();
+//     fpos(streamoff);
+//
+//     operator streamoff() const;
+//
+//     fpos& operator+=(streamoff);
+//     fpos  operator+ (fpos&) const;
+//     fpos& operator-=(streamoff);
+//     fpos  operator- (fpos&) const;
+//     fpos& operator= (fpos);
+// };
+
+int main(int, char**)
+{
+    ASSERT_SAME_TYPE(std::streampos, std::fpos<std::char_traits<char>::state_type>);
+
+    std::streampos p0;
+    assert(std::streamoff(p0) == 0);
+
+    std::streampos p1(1);
+    assert(std::streamoff(p1) == 1);
+
+    std::streampos p2 = 2;
+    assert(std::streamoff(p2) == 2);
+
+    assert(p2 != p1);
+
+    assert(std::streamoff(p1 + p2) == 3);
+    assert(std::streamoff(p2 - p1) == 1);
+
+    p0 += 5;
+    assert(std::streamoff(p0) == 5);
+    p0 -= 2;
+    assert(std::streamoff(p0) == 3);
+
+    assert((p0 + 3) == 6);
+    assert((p0 - 3) == 0);
+
+    return 0;
+}