Fix compilation under LLVM/clang with --enable-gcc-warnings

When compiling using clang (2.9 or lower) do not enable
-Wnormalized=id or -Woverride-init when --enable-gcc-warnings
or --enable-gcc-warnings-advisory is set as these options
are unsupported.

This commit is based on a patch for Tor
(git commit 56bdc844ba68ac0911efc7ad3398f1eafeaaac76 by Steven
Murdoch), Copyright (c) 2007-2011, The Tor Project, Inc.

diff --git a/configure.in b/configure.in
index 2cc091bcd92774237fdc65125e45291513d90a7d..c9c30c6a128a18ae1442e1eb30bd159201f605c3 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -635,6 +635,16 @@ if test x$enable_gcc_warnings = xyes && test "$GCC" = "yes"; then
 #error
 #endif])], have_gcc45=yes, have_gcc45=no)
 
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
+#if !defined(__clang__)
+#error
+#endif])], have_clang=yes, have_clang=no)
+
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
+#if !defined(__clang__) || (__clang_major__ > 2) || (__clang_major__ == 2 && __clang_minor__ > 9)
+#error
+#endif])], have_clang29orlower=yes, have_clang29orlower=no)
+
   CFLAGS="$CFLAGS -W -Wfloat-equal -Wundef -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wwrite-strings -Wredundant-decls -Wchar-subscripts -Wcomment -Wformat -Wwrite-strings -Wmissing-declarations -Wredundant-decls -Wnested-externs -Wbad-function-cast -Wswitch-enum -Werror"
   CFLAGS="$CFLAGS -Wno-unused-parameter -Wstrict-aliasing"
 
@@ -646,13 +656,27 @@ if test x$enable_gcc_warnings = xyes && test "$GCC" = "yes"; then
 
   if test x$have_gcc42 = xyes ; then
     # These warnings break gcc 4.0.2 and work on gcc 4.2
-    CFLAGS="$CFLAGS -Waddress -Wnormalized=id -Woverride-init"
+    CFLAGS="$CFLAGS -Waddress"
+  fi
+
+  if test x$have_gcc42 = xyes && test x$have_clang29orlower = xno; then
+    # These warnings break gcc 4.0.2 and clang, but work on gcc 4.2
+    # We only disable these for clang 2.9 and lower, in case they are
+    # supported in later versions.
+    CFLAGS="$CFLAGS -Wnormalized=id -Woverride-init"
   fi
 
   if test x$have_gcc45 = xyes ; then
     # These warnings work on gcc 4.5
     CFLAGS="$CFLAGS -Wlogical-op"
   fi
+
+  if test x$have_clang = xyes; then
+    # Disable the unused-function warnings, because these trigger
+    # for minheap-internal.h related code.
+    CFLAGS="$CFLAGS -Wno-unused-function"
+  fi
+
 ##This will break the world on some 64-bit architectures
 # CFLAGS="$CFLAGS -Winline"