build: define _GNU_SOURCE for .c files

This is needed for asprintf().

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>

diff --git a/Makefile.am b/Makefile.am
index 9408f4f71507b1bdfeb4979f96b09168333b9ee4..9c96785a94c9d0044fda2149cebec749a81a0171 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -11,7 +11,7 @@ ACLOCAL_AMFLAGS = -I m4
 LIBS =
 
 AM_CPPFLAGS = -I$(top_srcdir) -include $(top_srcdir)/config.h -Wextra
-AM_CPPFLAGS += -fvisibility=hidden
+AM_CPPFLAGS += -fvisibility=hidden -D_GNU_SOURCE
 
 lib_LTLIBRARIES = libgpiod.la