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

[Lei Zhang <zhanglei.april@gmail.com>]

2016-06-17 19:12 GMT+08:00 Lei Zhang <zhanglei.april@gmail.com>:
> 2016-06-16 21:42 GMT+08:00 Lei Zhang <zhanglei.april@gmail.com>:
>> 2016-06-16 21:13 GMT+08:00 Luca Barbato <lu_zero@gentoo.org>:
>>> On 16/06/16 14:47, Lei Zhang wrote:
>>>> 2016-06-16 17:43 GMT+08:00 Luca Barbato <lu_zero@gentoo.org>:
>>>>> 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.

Sorry, it should be "-U_GNU_SOURCE -D_XOPEN_SOURCE=700 -D_BSD_SOURCE"

Lei