Don't assume that compilers not named "clang" will, by default, report

an error, or not issue warnings, by default if you give them an unknown
-f flag.  Instead, test that flag with all compilers, and use -Werror to
force it to error out.

As with C/C++ flags, so with C++-only flags.

svn path=/trunk/; revision=50178

2 files changed, 24 insertions, 13 deletions

diff --git a/acinclude.m4 b/acinclude.m4
index a3c47fce18..3bef361b1b 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -1650,13 +1650,27 @@ if test "x$ac_supports_gcc_flags" = "xyes" ; then
   if test "$2" != CXX ; then
     #
     # Not C++-only; if this can be added to the C compiler flags, add them.
-    # Add $ac_wireshark_unknown_warning_option_error to make sure that
+    #
+    # If the option begins with "-W", add
+    # $ac_wireshark_unknown_warning_option_error to make sure that
     # we'll get an error if it's an unknown warning option; not all
     # compilers treat unknown warning options as errors (I'm looking at
     # you, clang).
     #
+    # If the option begins with "-f", add -Werror to make sure that
+    # we'll get an error if we get "argument unused during compilation"
+    # warnings, as those will either cause a failure for files compiled
+    # with -Werror or annoying noise for files compiled without it.
+    # (Yeah, you, clang.)
+    #
     CFLAGS_saved="$CFLAGS"
-    CFLAGS="$CFLAGS $ac_wireshark_unknown_warning_option_error $GCC_OPTION"
+    if expr "$GCC_OPTION" : "-W.*" >/dev/null
+    then
+      CFLAGS="$CFLAGS $ac_wireshark_unknown_warning_option_error $GCC_OPTION"
+    elif expr "$GCC_OPTION" : "-f.*" >/dev/null
+    then
+      CFLAGS="$CFLAGS -Werror $GCC_OPTION"
+    fi
     AC_COMPILE_IFELSE([
       AC_LANG_SOURCE([[
                         int foo;
@@ -1729,9 +1743,12 @@ if test "x$ac_supports_gcc_flags" = "xyes" ; then
     # C++-only; if this can be added to the C++ compiler flags, add them.
     #
     CXXFLAGS_saved="$CXXFLAGS"
-    CXXFLAGS="$CXXFLAGS $GCC_OPTION"
-    if test "x$CC" = "xclang" ; then
-      CXXFLAGS="$CXXFLAGS -Werror=unknown-warning-option"
+    if expr "$GCC_OPTION" : "-W.*" >/dev/null
+    then
+      CXXFLAGS="$CXXFLAGS $ac_wireshark_unknown_warning_option_error $GCC_OPTION"
+    elif expr "$GCC_OPTION" : "-f.*" >/dev/null
+    then
+      CXXFLAGS="$CXXFLAGS -Werror $GCC_OPTION"
     fi
     AC_LANG_PUSH([C++])
     AC_COMPILE_IFELSE([
diff --git a/configure.ac b/configure.ac
index f9883eb431..da7d663e32 100644
--- a/configure.ac
+++ b/configure.ac
@@ -643,15 +643,9 @@ bar(void)
 ## AC_WIRESHARK_GCC_CFLAGS_CHECK(-Wno-error=unused-but-set-variable)
 
 #
-# Use the faster pre gcc 4.5 floating point precision if available;
-# clang doesn't error out on -f options that it doesn't know about,
-# it just warns and ignores them, so this check doesn't cause us
-# to omit -fexcess-precision=fast, which produces a pile of
-# annoying warnings.
+# Use the faster pre gcc 4.5 floating point precision if available.
 #
-if test "x$CC" != "xclang" ; then
-  AC_WIRESHARK_GCC_CFLAGS_CHECK(-fexcess-precision=fast)
-fi
+AC_WIRESHARK_GCC_CFLAGS_CHECK(-fexcess-precision=fast)
 
 CFLAGS_before_fvhidden=$CFLAGS
 AC_WIRESHARK_GCC_CFLAGS_CHECK(-fvisibility=hidden)