Summary:
In D41064, I proposed adding `#pragma clang diagnostic ignored
"-Wuser-defined-literals"` to some of libc++'s headers, since these
warnings are now triggered by clang's new `-std=gnu++14` default:
```
$ cat test.cpp
#include <string>
$ clang -std=c++14 -Wsystem-headers -Wall -Wextra -c test.cpp
In file included from test.cpp:1:
In file included from /usr/include/c++/v1/string:470:
/usr/include/c++/v1/string_view:763:29: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string_view<char> operator "" sv(const char *__str, size_t __len)
^
/usr/include/c++/v1/string_view:769:32: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string_view<wchar_t> operator "" sv(const wchar_t *__str, size_t __len)
^
/usr/include/c++/v1/string_view:775:33: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string_view<char16_t> operator "" sv(const char16_t *__str, size_t __len)
^
/usr/include/c++/v1/string_view:781:33: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string_view<char32_t> operator "" sv(const char32_t *__str, size_t __len)
^
In file included from test.cpp:1:
/usr/include/c++/v1/string:4012:24: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string<char> operator "" s( const char *__str, size_t __len )
^
/usr/include/c++/v1/string:4018:27: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string<wchar_t> operator "" s( const wchar_t *__str, size_t __len )
^
/usr/include/c++/v1/string:4024:28: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string<char16_t> operator "" s( const char16_t *__str, size_t __len )
^
/usr/include/c++/v1/string:4030:28: warning: user-defined literal suffixes not starting with '_' are reserved [-Wuser-defined-literals]
basic_string<char32_t> operator "" s( const char32_t *__str, size_t __len )
^
8 warnings generated.
```
Both @aaron.ballman and @mclow.lists felt that adding this workaround to
the libc++ headers was the wrong way, and it should be fixed in clang
instead.
Here is a proposal to do just that. I verified that this suppresses the
warning, even when -Wsystem-headers is used, and that the warning is
still emitted for a declaration outside of system headers.
Reviewers: aaron.ballman, mclow.lists, rsmith
Reviewed By: aaron.ballman
Subscribers: mclow.lists, aaron.ballman, andrew, emaste, cfe-commits
Differential Revision: https://reviews.llvm.org/D41080
llvm-svn: 320755
Dimitry Andric