[alsa-devel] [PATCH] alsamixer: define _GNU_SOURCE to get exp10

[makepost at firemail.cc]

These flags vary between systems, on the Gentoo where I have access the 
Makefile generated from e1aa6d4 contains:

$ ack '^(AM|CURSES|NCURSESW)_CFLAGS' alsamixer/Makefile
CURSES_CFLAGS = -I/usr/include/ncursesw
NCURSESW_CFLAGS = -I/usr/include/ncursesw
AM_CFLAGS = -I/usr/include/ncursesw  -DCURSESINC="<ncurses.h>"

Files in /usr/include/ncursesw don't mention _GNU_SOURCE so I'm baffled 
where GCC gets it from.

Indeed the local alsamixer/Makefile.am is a more suitable place to put 
the flag. A newbie question follows, should I somehow update the patch 
with your edit and reply to this message, or did you generate the diff 
from an already edited version?

On 2019-01-16 14:22, Jaroslav Kysela wrote:
> Dne 16.1.2019 v 02:35 makepost at firemail.cc napsal(a):
>> Fixes Master, Headphones and Speaker stuck at -8 percentage after
>> building with Clang 7.0.1 and getting warned about implicit 
>> declaration
>> of exp10, which is behind _GNU_SOURCE as a non-standard feature. 
>> Thanks
>> Takashi Iwai for the CFLAGS suggestion on the mailing list. GCC build 
>> is
>> not affected, so not adding a compiler check to the configure script.
>> 
>> uClibc-ng has got exp10 since 1.0.12, so the fallback macro is no 
>> longer
>> needed. However, alsa-utils relies on gettext so might need further
>> patches to actually work on uClibc systems.
>> 
>> Signed-off-by: makepost <makepost at firemail.cc>
>> 
>> diff --git a/alsamixer/volume_mapping.c b/alsamixer/volume_mapping.c
>> index 94bd0fe..48cfbe2 100644
>> --- a/alsamixer/volume_mapping.c
>> +++ b/alsamixer/volume_mapping.c
>> @@ -36,11 +36,6 @@
>>   #include <stdbool.h>
>>   #include "volume_mapping.h"
>> 
>> -#ifdef __UCLIBC__
>> -/* 10^x = 10^(log e^x) = (e^x)^log10 = e^(x * log 10) */
>> -#define exp10(x) (exp((x) * log(10)))
>> -#endif /* __UCLIBC__ */
>> -
>>   #define MAX_LINEAR_DB_SCALE    24
>> 
>>   static inline bool use_linear_dB_scale(long dBmin, long dBmax)
>> diff --git a/configure.ac b/configure.ac
>> index 7938996..0d54942 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -350,6 +350,8 @@ if test x$alsamixer = xtrue; then
>> 
>> 
>>     AC_MSG_RESULT([$CURSESLIB])
>> +
>> +  CFLAGS="$CFLAGS -D_GNU_SOURCE"
> 
> It would be propably better to put this to the local makefile for 
> alsamixer:
> 
> diff --git a/alsamixer/Makefile.am b/alsamixer/Makefile.am
> index 259b29e..249e8f8 100644
> --- a/alsamixer/Makefile.am
> +++ b/alsamixer/Makefile.am
> @@ -1,4 +1,4 @@
> -AM_CFLAGS = @CURSES_CFLAGS@ -DCURSESINC="@CURSESINC@"
> +AM_CFLAGS = -D_GNU_SOURCE @CURSES_CFLAGS@ -DCURSESINC="@CURSESINC@"
>  LDADD = @CURSESLIB@
> 
>  bin_PROGRAMS = alsamixer
> 
> The reason, why the problem is not visible with the standard
> gcc/glibc/ncurses is that this definition is activated by ncurses:
> 
> $ find alsamixer -type f -exec grep -H GNU_SOURCE {} \;
> alsamixer/Makefile:CURSES_CFLAGS = -D_GNU_SOURCE -D_DEFAULT_SOURCE
> alsamixer/Makefile:NCURSESW_CFLAGS = -D_GNU_SOURCE -D_DEFAULT_SOURCE
> alsamixer/Makefile:AM_CFLAGS = -D_GNU_SOURCE -D_DEFAULT_SOURCE
> -DCURSESINC="<ncurses.h>"
> 
> 					Jaroslav