Use -Wold-style-definition

[Joseph Myers]

This patch makes glibc build with -Wold-style-definition to avoid
old-style function definitions creeping back in by accident.

Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).  Also tested build for arm,
mips64 and powerpc32.  Hopefully there aren't any remaining
system-specific files with old-style definitions whose formatting
evaded my searches, but if there are, they will be easy to fix.

2015-10-21  Joseph Myers  <joseph@codesourcery.com>

	* Makeconfig (+gccwarn-c): Add -Wold-style-definition.
	* Makefile ($(objpfx)c++-types-check.out): Filter out
	$(+gccwarn-c) instead of -Wstrict-prototypes.

diff --git a/Makeconfig b/Makeconfig
index 1dc522c..f3668c6 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -752,7 +752,7 @@ endif
 ifeq ($(enable-werror),yes)
 +gccwarn += -Werror
 endif
-+gccwarn-c = -Wstrict-prototypes
++gccwarn-c = -Wstrict-prototypes -Wold-style-definition
 
 # We do not depend on the address of constants in different files to be
 # actually different, so allow the compiler to merge them all.
diff --git a/Makefile b/Makefile
index a2abfb9..b2dd771 100644
--- a/Makefile
+++ b/Makefile
@@ -256,7 +256,7 @@ ifneq ($(CXX),no)
 vpath c++-types.data $(+sysdep_dirs)
 
 $(objpfx)c++-types-check.out: c++-types.data scripts/check-c++-types.sh
-	scripts/check-c++-types.sh $< $(CXX) $(filter-out -std=gnu99 -Wstrict-prototypes,$(CFLAGS)) $(CPPFLAGS) > $@; \
+	scripts/check-c++-types.sh $< $(CXX) $(filter-out -std=gnu99 $(+gccwarn-c),$(CFLAGS)) $(CPPFLAGS) > $@; \
 	$(evaluate-test)
 endif
 

-- 
Joseph S. Myers
joseph@codesourcery.com