[FFmpeg-devel] [PATCHv2] configure: add -D_DEFAULT_SOURCE to silence -Wcpp

[Ganesh Ajjanagadde]

Glibc 2.20 onwards generates a deprecation warning for usage of _BSD_SOURCE and _SVID_SOURCE.
The solution from man feature_test_macros is to define both _DEFAULT_SOURCE and the old macros.
This change is done in configure while testing for Glibc. Doing it in source code
would require __UCLIBC__ checks, etc since uclibc also defines __GLIBC__ and __GLIBC_MINOR__,
so placing it in configure avoids the repeated checks.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
---
 configure                | 6 ++++++
 libavformat/os_support.c | 1 -
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index cd6f629..0cd0a6c 100755
--- a/configure
+++ b/configure
@@ -4520,6 +4520,12 @@ probe_libc(){
     elif check_${pfx}cpp_condition features.h "defined __GLIBC__"; then
         eval ${pfx}libc_type=glibc
         add_${pfx}cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600
+        # define _DEFAULT_SOURCE for glibc 2.20 onwards to silence deprecation
+        # warnings for _BSD_SOURCE and _SVID_SOURCE.
+        if check_${pfx}cpp_condition features.h "(__GLIBC__ == 2 && __GLIBC_MINOR__ >= 20) \
+            || (__GLIBC__ > 2)"; then
+            add_${pfx}cppflags -D_DEFAULT_SOURCE
+        fi
     # MinGW headers can be installed on Cygwin, so check for newlib first.
     elif check_${pfx}cpp_condition newlib.h "defined _NEWLIB_VERSION"; then
         eval ${pfx}libc_type=newlib
diff --git a/libavformat/os_support.c b/libavformat/os_support.c
index 7950e44..3c22631 100644
--- a/libavformat/os_support.c
+++ b/libavformat/os_support.c
@@ -21,7 +21,6 @@
  */
 
 /* needed by inet_aton() */
-#define _DEFAULT_SOURCE
 #define _SVID_SOURCE
 
 #include "config.h"
-- 
2.5.2