[vlc-devel] [PATCH] contrib/libpng: force C89 mode when using GCC (fixes #16760)

[Sean McGovern]

---
Apparently this library lives 20+ years in the past...
---
 contrib/src/png/force-c89.patch |   34 ++++++++++++++++++++++++++++++++++
 contrib/src/png/rules.mak       |    3 ++-
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 contrib/src/png/force-c89.patch

diff --git a/contrib/src/png/force-c89.patch b/contrib/src/png/force-c89.patch
new file mode 100644
index 0000000..1877df4
--- /dev/null
+++ b/contrib/src/png/force-c89.patch
@@ -0,0 +1,34 @@
+From 12e63e91af1378225993b36e25ce3252b54e751a Mon Sep 17 00:00:00 2001
+From: Dagobert Michelsen <dam at opencsw.org>
+Date: Mon, 14 Mar 2016 16:21:06 +0100
+Subject: [PATCH] Force back to C89 if needed. This fixes #245
+
+---
+ configure.ac | 14 ++++++++++++++
+ 1 file changed, 14 insertions(+)
+
+diff --git a/configure.ac b/configure.ac
+index 3b8746a..ee3ea05 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -114,6 +114,20 @@ AC_ARG_ENABLE(werror,
+       CFLAGS="$sav_CFLAGS"
+     fi],)
+ 
++# For GCC 5 the default mode for C is -std=gnu11 instead of -std=gnu89
++# In pngpriv.h we request just the POSIX 1003.1 and C89 APIs by defining _POSIX_SOURCE to 1
++# This is incompatible with the new default mode, so we test for that and force the 
++AC_MSG_CHECKING([if we need to force back C standard to C89])
++AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#define _POSIX_SOURCE 1
++#include <stdio.h>
++])],AC_MSG_RESULT(no),[
++if test "x$GCC" != "xyes"; then
++  AC_MSG_ERROR([Forcing back to C89 is required but the flags are unknown for other compilers than GCC])
++fi
++AC_MSG_RESULT(yes)
++CFLAGS="$CFLAGS -std=c89"
++])
++
+ # Checks for header files.
+ AC_HEADER_STDC
+ 
diff --git a/contrib/src/png/rules.mak b/contrib/src/png/rules.mak
index 61f835e..0cde547 100644
--- a/contrib/src/png/rules.mak
+++ b/contrib/src/png/rules.mak
@@ -17,12 +17,13 @@ png: libpng-$(PNG_VERSION).tar.xz .sum-png
 	$(APPLY) $(SRC)/png/winrt.patch
 	$(APPLY) $(SRC)/png/bins.patch
 	$(APPLY) $(SRC)/png/automake.patch
+	$(APPLY) $(SRC)/png/force-c89.patch
 	$(MOVE)
 
 DEPS_png = zlib $(DEPS_zlib)
 
 .png: png
 	$(RECONF)
-	cd $< && $(HOSTVARS) ./configure $(HOSTCONF)
+	cd $< && $(HOSTVARS) CC="`echo ${CC} | ${SED-sed} 's: -std=[a-z0-9]*::'`" ./configure $(HOSTCONF)
 	cd $< && $(MAKE) install
 	touch $@
-- 
1.7.9.2