[libgsf] Compilation: improve clang support.

[Morten Welinder <mortenw src gnome org>]

commit 5d8d1e17a51407c75da92f0e1a5f33114a6554ee
Author: Morten Welinder <terra gnome org>
Date:   Sun Feb 17 16:53:57 2013 -0500

    Compilation: improve clang support.
    
    And fix a few minor problems it finds.

 ChangeLog               |    4 ++++
 configure.ac            |   39 +++++++++++++++++++++++++++++----------
 gsf/gsf-blob.c          |    2 +-
 gsf/gsf-clip-data.c     |    2 +-
 gsf/gsf-doc-meta-data.c |    2 +-
 5 files changed, 36 insertions(+), 13 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 3f2e5fa..4f8c4ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2013-02-17  Morten Welinder  <terra gnome org>
+
+       * configure.ac (set_more_warnings): Improve support for clang.
+
 2013-02-05  Jean Brefort  <jean brefort normalesup org>
 
        * doc/gsf-sections.txt: fix gtk-doc warnings.
diff --git a/configure.ac b/configure.ac
index a8e1772..f19ff00 100644
--- a/configure.ac
+++ b/configure.ac
@@ -163,26 +163,44 @@ AC_SUBST(TYPELIBDIR)
 ## this should come after `AC_PROG_CC'
 ifdef([GNOME_COMPILE_WARNINGS],[GNOME_COMPILE_WARNINGS],)
 CFLAGS="$CFLAGS $WARN_CFLAGS -DG_DISABLE_DEPRECATED"
-if test "$GCC" = "yes"; then
-       warning_options="-Wsign-compare -Wpointer-arith -Wnested-externs \
+
+set_more_warnings=yes
+if test "$GCC" = yes -a "x$set_more_warnings" != xno; then
+       dnl Clang needs to option, or else it will appear to support any
+       dnl warning option
+       uwoption="-Werror=unknown-warning-option"
+       SAVE_CFLAGS="$CFLAGS"
+       CFLAGS="$CFLAGS $uwoption"
+       AC_MSG_CHECKING([whether gcc understands $uwoption])
+       AC_COMPILE_IFELSE(
+               [AC_LANG_PROGRAM([], [])],
+               [has_unknown_warning_option=yes],
+               [has_unknown_warning_option=no; uwoption=""])
+       AC_MSG_RESULT($has_unknown_warning_option)
+       CFLAGS="$SAVE_CFLAGS"
+
+       warning_options="-Wsign-compare -Wpointer-arith \
                         -Wchar-subscripts -Wwrite-strings \
                         -Wdeclaration-after-statement -Wnested-externs \
-                        -Wmissing-noreturn -Wmissing-prototypes \
+                        -Wmissing-noreturn \
                         -Werror=missing-prototypes -Werror=nested-externs \
                         -Werror=implicit-function-declaration \
                         -Wmissing-declarations -Wno-pointer-sign \
                         -Werror=format-security -Wbitwise -Wcast-to-as \
                         -Wdefault-bitfield-sign -Wdo-while -Wparen-string \
-                        -Wptr-subtraction-blows -Wreturn-void -Wtypesign"
+                        -Wptr-subtraction-blows -Wreturn-void -Wtypesign \
+                        -Wstrict-prototypes"
        for option in $warning_options ; do
                SAVE_CFLAGS="$CFLAGS"
-               CFLAGS="$CFLAGS $option"
+               CFLAGS="$CFLAGS $uwoption $option"
                AC_MSG_CHECKING([whether gcc understands $option])
-               AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
-                       has_option=yes,
-                       has_option=no)
-               if test $has_option = no; then
-                 CFLAGS="$SAVE_CFLAGS"
+               AC_COMPILE_IFELSE(
+                       [AC_LANG_PROGRAM([], [])],
+                       [has_option=yes],
+                       [has_option=no])
+               CFLAGS="$SAVE_CFLAGS"
+               if test $has_option = yes; then
+                       CFLAGS="$CFLAGS $option"
                fi
                AC_MSG_RESULT($has_option)
                unset has_option
@@ -190,6 +208,7 @@ if test "$GCC" = "yes"; then
        done
        unset option
 fi
+AC_SUBST(WARN_CFLAGS)
 
 AC_CHECK_DECL(fdopen, fdopen_works=yes, fdopen_works=no)
 if test $fdopen_works = no ; then
diff --git a/gsf/gsf-blob.c b/gsf/gsf-blob.c
index 5382b1c..d22f751 100644
--- a/gsf/gsf-blob.c
+++ b/gsf/gsf-blob.c
@@ -73,7 +73,7 @@ gsf_blob_init (GsfBlob *blob)
 
 GSF_CLASS (GsfBlob, gsf_blob,
           gsf_blob_class_init, gsf_blob_init,
-          G_TYPE_OBJECT);
+          G_TYPE_OBJECT)
 
 
 /**
diff --git a/gsf/gsf-clip-data.c b/gsf/gsf-clip-data.c
index 60f80b0..63a5f5f 100644
--- a/gsf/gsf-clip-data.c
+++ b/gsf/gsf-clip-data.c
@@ -81,7 +81,7 @@ gsf_clip_data_class_init (GObjectClass *gobject_class)
 
 GSF_CLASS (GsfClipData, gsf_clip_data,
           gsf_clip_data_class_init, gsf_clip_data_init,
-          G_TYPE_OBJECT);
+          G_TYPE_OBJECT)
 
 /**
  * gsf_clip_data_new:
diff --git a/gsf/gsf-doc-meta-data.c b/gsf/gsf-doc-meta-data.c
index b117119..c51c0ce 100644
--- a/gsf/gsf-doc-meta-data.c
+++ b/gsf/gsf-doc-meta-data.c
@@ -235,7 +235,7 @@ gsf_doc_meta_data_size (GsfDocMetaData const *meta)
 }
 
 static void
-cb_print_property (G_GNUC_UNUSED char const *name,
+cb_print_property (char const *name,
                   GsfDocProp const *prop)
 {
        if (gsf_doc_prop_get_link (prop) != NULL)