enable gcc warnings

Enable all useful warnings which were also enabled in MPD.  Steal
m4/mpd_check_cflag.m4 from MPD.

diff --git a/configure.ac b/configure.ac
index 3ffc870097dd9a2e76052610acfe639514afaa4b..16a13571d1c0dba76dc1ce49d633516e56217db8 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -206,9 +206,24 @@ AC_ARG_ENABLE([debug],
              [enable_debug=no])
 AC_MSG_RESULT([$enable_debug])
 if test "x$enable_debug" = "xyes" ; then
-   CFLAGS="$CFLAGS -Wall -g -DDEBUG"
+   CFLAGS="$CFLAGS -g -DDEBUG"
 fi
 
+dnl CFLAGS
+
+AC_SUBST(AM_CFLAGS)
+
+CHECK_CFLAG([-Wall])
+CHECK_CFLAG([-Wextra])
+CHECK_CFLAG([-Wno-deprecated-declarations])
+CHECK_CFLAG([-Wmissing-prototypes])
+CHECK_CFLAG([-Wdeclaration-after-statement])
+CHECK_CFLAG([-Wshadow])
+CHECK_CFLAG([-Wpointer-arith])
+CHECK_CFLAG([-Wstrict-prototypes])
+CHECK_CFLAG([-Wcast-qual])
+CHECK_CFLAG([-Wwrite-strings])
+
 dnl Optional screen - help screen
 #AC_MSG_CHECKING([whether to include the help screen])
 #AC_ARG_ENABLE([help-screen], 

diff --git a/m4/cflags.m4 b/m4/cflags.m4
new file mode 100644 (file)
index 0000000..cc6d5fa
--- /dev/null
+++ b/m4/cflags.m4
@@ -0,0 +1,15 @@
+AC_DEFUN([CHECK_CFLAG], [
+    var=`echo "$1" | tr "=-" "__"`
+    AC_CACHE_CHECK([whether the C compiler accepts $1],[check_cflag_$var],[
+        save_CFLAGS="$CFLAGS"
+        CFLAGS="$CFLAGS $1"
+        AC_COMPILE_IFELSE([int main(void) { return 0; }],
+            [eval "check_cflag_$var=yes"],
+            [eval "check_cflag_$var=no"])
+        CFLAGS="$save_CFLAGS"
+        ])
+    if eval "test x`echo '$check_cflag_'$var` = xyes"; then
+        AM_CFLAGS="$AM_CFLAGS $1"
+    fi
+    ])
+])