[PATCH] RFC: PR78905 define _GLIBCXX_RELEASE macro

[Ed Smith-Rowland]

On 01/17/2017 04:55 PM, Ed Smith-Rowland wrote:
> On 01/17/2017 12:25 PM, Jonathan Wakely wrote:
>> As I said in https://gcc.gnu.org/ml/libstdc++/2017-01/msg00109.html
>> the __GLIBCXX__ macro is useless, but is the closest thing we have to
>> a version macro for libstdc++. This matters when using libstdc++ with
>> Clang or Intel icc or other compilers, because you can't check the
>> __GNUC__ macro. I've seen several requests for a way to check the
>> libstdc++ version, or complaints that there is no way to do it.
>>
>> This patch adds a new _GLIBCXX_RELEASE macro that contains the same
>> value as __GNUC__ i.e. the major release number.
>>
>> - Yes, it only contains the major number. We could in theory have
>>  _GLIBCXX_MAJOR and _GLIBCXX_MINOR instead, but between
>>  _GLIBCXX_RELEASE and __GLIBCXX__ you can identify the release branch
>>  and a date within that branch.
>>
>> - The name is "RELEASE" because we used to define _GLIBCXX_VERSION
>>  many years ago, but it was a string literal and this is an integer.
>>  To avoid problems for any old code checking for _GLIBCXX_VERSION I
>>  chose a different name.
>>
>> Thoughts?
>>
>>
>>     PR libstdc++/78905
>>     * include/Makefile.am (_GLIBCXX_RELEASE): Set value.
>>     * include/Makefile.in: Regenerate.
>>     * include/bits/c++config (_GLIBCXX_RELEASE): Add #define.
>>     * testsuite/ext/profile/mutex_extensions_neg.cc: Use lineno of 0 in
>>     dg-error.
>>
> This might stop people from complaining about stub implementations.
>
> It would also help with ABI breaks and as a coarse-grained feature-macro.
>
> It seems like we'd want to backport this of course.
>
> Of course you want more feedback from packagers.
>
> Ed
>
>
I'm assuming this is really directed at folks who borrow only the 
library and not the rest of gcc.

Otherwise we could just use the main macro.