Subscribe to particular warning flags, not to -Wextra.

-Wextra now entails -Wcast-function-type, which is incompatible with
various Unix APIs like sigaction.

diff --git a/src/microcode/configure.ac b/src/microcode/configure.ac
index 895bab4c9a7d2d244b79a6de9ef1fe7bc6d97b56..300baf74f8f7dea92bf8d4ce019897c155737a5b 100644 (file)
--- a/src/microcode/configure.ac
+++ b/src/microcode/configure.ac
@@ -212,24 +212,27 @@ if test ${GCC} = yes; then
     CFLAGS="-Wstrict-prototypes -Wnested-externs -Wredundant-decls ${CFLAGS}"
     CFLAGS_WERROR=-Werror
 
-    AC_MSG_CHECKING([for GCC>=4])
-    AC_COMPILE_IFELSE(
-       [AC_LANG_PROGRAM(
-           [[
-           #if __GNUC__ >= 4
-           ;
-           #else
-           #error "gcc too old"
-           #endif
-           ]],
-           [[]]
-       )],
-       [
-       AC_MSG_RESULT([yes])
-       CFLAGS="-Wextra -Wno-sign-compare -Wno-unused-parameter ${CFLAGS}"
-       CFLAGS="-Wold-style-definition ${CFLAGS}"
-       ],
-       [AC_MSG_RESULT([no])])
+    for flag in \
+       -Wclobbered \
+       -Wempty-body \
+       -Wignored-qualifiers \
+       -Wimplicit-fallthrough \
+       -Wmissing-field-initializers \
+       -Wmissing-parameter-type \
+       -Wold-style-declaration \
+       -Woverride-init \
+       -Wtype-limits \
+       -Wuninitialized \
+       -Wshift-negative-value \
+       ; do
+       AC_MSG_CHECKING([for compiler warning $flag])
+       SAVED_CFLAGS="$CFLAGS"
+       CFLAGS="$CFLAGS $flag"
+       AC_TRY_COMPILE([],[],
+           [AC_MSG_RESULT(yes)],
+           [AC_MSG_RESULT(no)
+           CFLAGS="$SAVED_CFLAGS"])
+    done
 
     # other possibilities:
     # -Wmissing-prototypes -Wunreachable-code -Wwrite-strings