Add an autoconf test to check for optional compiler flags like

-Wno-missing-field-initializers or -Wno-variadic-macros.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85147 91177308-0d34-0410-b5e6-96231b3b80d8

Makefile.config.in

@@ -320,3 +320,9 @@ ENABLE_LLVMC_DYNAMIC = 0
 # support (via the -load option).
 ENABLE_LLVMC_DYNAMIC_PLUGINS = 1
 #@ENABLE_LLVMC_DYNAMIC_PLUGINS@
+
+# Optional flags supported by the compiler
+# -Wno-missing-field-initializers
+NO_MISSING_FIELD_INITIALIZERS = @NO_MISSING_FIELD_INITIALIZERS@
+# -Wno-variadic-macros
+NO_VARIADIC_MACROS = @NO_VARIADIC_MACROS@

autoconf/configure.ac

@@ -943,6 +943,12 @@ fi
 dnl Tool compatibility is okay if we make it here.
 AC_MSG_RESULT([ok])
 
+dnl Check optional compiler flags. 
+AC_MSG_CHECKING([optional compiler flags])
+CXX_FLAG_CHECK(NO_VARIADIC_MACROS, [-Wno-variadic-macros])
+CXX_FLAG_CHECK(NO_MISSING_FIELD_INITIALIZERS, [-Wno-missing-field-initializers])
+AC_MSG_RESULT([$NO_VARIADIC_MACROS $NO_MISSING_FIELD_INITIALIZERS])
+
 dnl===-----------------------------------------------------------------------===
 dnl===
 dnl=== SECTION 5: Check for libraries

autoconf/m4/cxx_flag_check.m4

@@ -0,0 +1,2 @@
+AC_DEFUN([CXX_FLAG_CHECK],
+  [AC_SUBST($1, `$CXX $2 -fsyntax-only -xc /dev/null 2>/dev/null && echo $2`)])