Implement LWG 3296

[mclow.lists]

Summary

https://cplusplus.github.io/LWG/issue3296 says that the call
basic_regex& assign(const charT* ptr, size_t len, flag_type f);
is specified twice: once with a default value for f, and once without.

This patch adds the default value regex_constants::ECMAScript to the final parameter.

Note that MS-STL already has this behavior, while libstdc++ does not.

[mclow.lists]

libcxx/include/regex

179

Most of this change is just lining up stuff to make it easy to see that it's all the same. The only actual change is line 173

[EricWF]

Can you use clang-format instead of custom formatting?

Should we leave some comment or trace that LWG 3296 is complete or has nothing to do when it actually gets accepted?

Otherwise, LGTM.

[mclow.lists]

In D67944#1681085, @EricWF wrote:

Can you use clang-format instead of custom formatting?

clang-format would destroy the structure that I added.
Adding that structure was the whole point of the edit (other than line 173, obviously)

Should we leave some comment or trace that LWG 3296 is complete or has nothing to do when it actually gets accepted?

I'll just remember. When I make the list of issues to be resolved for Belfast, I will note that "we already do this"

Otherwise, LGTM.

Thanks.

[jwakely]

Note that MS-STL already has this behavior, while libstdc++ does not.

Thanks for the heads-up, I've added the default argument in https://gcc.gnu.org/r276121

[mclow.lists]

Committed as revision 372896

libcxx/include/regex

     // assign:
     basic_regex& assign(const basic_regex& that);
     basic_regex& assign(basic_regex&& that) noexcept;
-    basic_regex& assign(const charT* ptr, flag_type f = regex_constants::ECMAScript);
-    basic_regex& assign(const charT* p, size_t len, flag_type f);
+    basic_regex& assign(const charT* ptr,           flag_type f = regex_constants::ECMAScript);
+    basic_regex& assign(const charT* p, size_t len, flag_type f = regex_constants::ECMAScript);
     template <class string_traits, class A>
         basic_regex& assign(const basic_string<charT, string_traits, A>& s,
                                                     flag_type f = regex_constants::ECMAScript);
     template <class InputIterator>
         basic_regex& assign(InputIterator first, InputIterator last,
                                                     flag_type f = regex_constants::ECMAScript);
-    basic_regex& assign(initializer_list<charT>, flag_type = regex_constants::ECMAScript);
+    basic_regex& assign(initializer_list<charT>,    flag_type = regex_constants::ECMAScript);
 
     // const operations:
     unsigned mark_count() const;

     basic_regex& assign(const value_type* __p, flag_type __f = regex_constants::ECMAScript)
         {return assign(__p, __p + __traits_.length(__p), __f);}
     _LIBCPP_INLINE_VISIBILITY
-    basic_regex& assign(const value_type* __p, size_t __len, flag_type __f)
+    basic_regex& assign(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
         {return assign(__p, __p + __len, __f);}
     template <class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY

libcxx/test/std/re/re.regex/re.regex.assign/assign_ptr_size_flag.pass.cpp

 
 int main(int, char**)
 {
+    std::regex r0;
+    r0.assign("(a([bc]))", 9);
+    assert(r0.flags() == std::regex::ECMAScript);
+    assert(r0.mark_count() == 2);
+
+    std::regex r1;
+    r1.assign("(a([bc]))", 9, std::regex::ECMAScript);
+    assert(r1.flags() == std::regex::ECMAScript);
+    assert(r1.mark_count() == 2);
+
     std::regex r2;
     r2.assign("(a([bc]))", 9, std::regex::extended);
     assert(r2.flags() == std::regex::extended);