Cygwin64 build fails for ffserver.o

[Tim Kiselev]

See ​http://fate.ffmpeg.org/history.cgi?slot=x86_64-win10-cygwin-gcc-5.4.0
Failing since revision N-81748-g47ea6f5, last checked on N-81780-g4a05d2e

% git reset --hard "origin/N-81748-g47ea6f5"
HEAD is now at 47ea6f5 lavd: drop SDL1 device and SDL1 support
% cd ../build
% ../src/configure --enable-gpl --enable-avresample
.....
% make
.....
src/ffserver.c: In function ‘main’:
src/ffserver.c:4003:5: error: implicit declaration of function ‘sigaction’ [-Werror=implicit-function-declaration]
     sigaction(SIGCHLD, &sigact, 0);
     ^
cc1: some warnings being treated as errors
make: *** [/tmp/fate/build/src/common.mak:60: ffserver.o] Error 1

Fixed by using

% make CFLAGS="-Wno-error=implicit-function-declaration"
(build finishes normally)

[Tim Kiselev]

Actually, disabling the error breaks other parts of the build, so it's not a fix.

[Carl Eugen Hoyos]

Building does not work with --extra-cflags=-Wno-error=implicit-function-declaration?

[Timo R.]

Defining _XOPEN_SOURCE or _GNU_SOURCE makes it work for me.

[Carl Eugen Hoyos]

How does CPPFLAGS (in config.mak) look like?

[Tim Kiselev]

CPPFLAGS= -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -U__STRICT_ANSI__ -DPIC -DZLIB_CONST

I'm not really that experienced in C development, so I'm kinda just poking around.

[Timo R.]

Fixed with b7bd5b9794223f12203142159a22b176da2378e8