Re: [gentoo-musl] [GSoC] _GNU_SOURCE in C++

[Lei Zhang]

2016-06-16 21:42 GMT+08:00 Lei Zhang <zhanglei.april@×××××.com>:
> 2016-06-16 21:13 GMT+08:00 Luca Barbato <lu_zero@g.o>:
>> On 16/06/16 14:47, Lei Zhang wrote:
>>> 2016-06-16 17:43 GMT+08:00 Luca Barbato <lu_zero@g.o>:
>>>> On 16/06/16 05:36, Lei Zhang wrote:
>>>>> Attached is what I've got so far.
>>>>>
>>>>> Some of them are not documented in man pages, so I checked their
>>>>> declarations in musl's headers. Functions strtold_l, strtoll_l and
>>>>> strtoull_l are not available in musl, but libc++ is smart enough to
>>>>> not use them when linked against musl.
>>>
>>> I made a mistake. Actually strtold_l *is* available in musl, but
>>> hidden by _GNU_SOURCE.
>>
>> Not hidden by _BSD_SOURCE as well?
>
> No, only by _GNU_SOURCE.
>
>>>> beside vasprintf, the rest is covered by _XOPEN_SOURCE 700
>>>>
>>>> Might be worth trying to do -U_GNU_SOURCES -D_XOPEN_SOURCE=700 and see
>>>> how it goes.
>>>
>>> So far vasprintf and strtold_l are not covered. vasprintf can be
>>> covered with -D_BSD_SOURCE. But _BSD_SOURCE is deprecated since glibc
>>> 2.20; I don't know if this has any impact on musl.
>>
>> It should not and -D_BSD_SOURCE should be fine for musl.
>
> I just found that vasprintf is only protected by _GNU_SOURCE in glibc,
> which means in this case _BSD_SOURCE only works for musl.
>
>>>> How vasprintf is used?
>>>
>>> It's used by <locale>. The code is kinda hard to read; I can't tell
>>> exactly what it's doing...
>>
>> same for the _l variants I guess.
>
> So what now? So far strtold_l still needs _GNU_SOURCE in musl;
> strtold_l, strtoll_l, strtoull_l and vasprintf all need _GNU_SOURCE in
> glibc.

To sum it up:

* As for musl, "-U_GNU_SOURCES -U_GNU_SOURCES=700 -D_BSD_SOURCE"
covers every symbol needed by libc++ except for strtold_l.

* As for glibc, "-U_GNU_SOURCE -D_ISOC11_SOURCE -D_DEFAULT_SOURCE"
covers everything except for strtold_l, strtoll_l, strtoull_l and
vasprintf.


Lei