[cfe-dev] Clang++ always defines _GNU_SOURCE

[Lei Zhang via cfe-dev]

2016-06-14 17:59 GMT+08:00 Ismail Donmez <ismail at i10z.com>:
> Hi,
>
> On Tue, Jun 14, 2016 at 12:54 PM, Lei Zhang via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
>> 2016-06-14 16:54 GMT+08:00 Eric Fiselier <eric at efcs.ca>:
>>>>  Does libc++ also rely on this macro to work on Linux?
>>>
>>> Yes. Adding -U_GNU_SOURCE during the libc++ build results in a litany of
>>> errors.
>>> The libc++ headers depend on a number of C library symbols that only get
>>> defined when -D_GNU_SOURCE=1 is present.
>>
>> Is it feasible to use some finer-grain control like _ISOC99_SOURCE,
>> instead of resorting to the too versatile _GNU_SOURCE?
>>
>> I'd be willing to work out such a patch to libc++, if it makes sense.
>
> Note that _GNU_SOURCE is more extensive:

Yes, it requires the use of multiple different finer-grain macros to
replace _GNU_SOURCE, but it's worth the effort IMHO. Simply defining
_GNU_SOURCE may pollute users' code with many unwanted symbols.


Lei