[Bug middle-end/21850] [4.0 Regression] misscompiling comparision from vector to integer

[palves at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21850

--- Comment #6 from palves at gcc dot gnu.org ---
Author: palves
Date: Fri Sep 15 14:53:48 2017
New Revision: 252822

URL: https://gcc.gnu.org/viewcvs?rev=252822=gcc=rev
Log:
Fix compile time error when using ansidecl.h with an old version of GCC.

include/
2017-07-31  Nick Clifton  <ni...@redhat.com>

Binutils PR 21850
* ansidecl.h (OVERRIDE): Protect check of __cplusplus value with
#idef __cplusplus.

Modified:
trunk/include/ChangeLog
trunk/include/ansidecl.h

[Bug c++/80265] __builtin_{memcmp,memchr,strlen} are not usable in constexpr functions

[palves at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80265

--- Comment #19 from palves at gcc dot gnu.org ---
Author: palves
Date: Mon Jun 12 22:22:39 2017
New Revision: 249137

URL: https://gcc.gnu.org/viewcvs?rev=249137=gcc=rev
Log:
Finish implementing P0426R1 "Constexpr for std::char_traits" for C++17

As discussed in PR c++/80265 ("__builtin_{memcmp,memchr,strlen} are
not usable in constexpr functions"), use __builtin_constant_p to tell
whether we can defer to a constexpr algorithm.

I used __always_inline__ just to be thorough.  It isn't really really
necessary as far as I could determine.

Changes like these:

 if (__n == 0)
   return 0;
 -  return wmemcmp(__s1, __s2, __n);
 +  else
 +return wmemcmp(__s1, __s2, __n);

are necessary otherwise G++ complains that we're calling a
non-constexpr function, which looks like a a manifestation of PR67026
to me.

libstdc++-v3:
2017-06-12  Pedro Alves  <pal...@redhat.com>

* doc/xml/manual/status_cxx2017.xml: Update C++17 constexpr
char_traits status.
* doc/html/*: Regenerate.

* include/bits/char_traits.h (_GLIBCXX_ALWAYS_INLINE): Define if
not already defined.
(__cpp_lib_constexpr_char_traits): Uncomment.
(__constant_string_p, __constant_char_array_p): New.
(std::char_traits, std::char_traits): Add
_GLIBCXX17_CONSTEXPR on compare, length and find and use
__constant_string_p, __constant_char_array_p and
__builtin_constant_p to defer to __gnu_cxx::char_traits at compile
time.

* testsuite/21_strings/char_traits/requirements/
constexpr_functions_c++17.cc: Uncomment
__cpp_lib_constexpr_char_traits tests.  Uncomment
test_compare, test_length, test_find,
test_compare, test_length and test_find
static_assert tests.

Modified:
trunk/libstdc++-v3/ChangeLog
trunk/libstdc++-v3/doc/xml/manual/status_cxx2017.xml
trunk/libstdc++-v3/include/bits/char_traits.h
   
trunk/libstdc++-v3/testsuite/21_strings/char_traits/requirements/constexpr_functions_c++17.cc