[libgsf] Compilation: copy warning setup from gnumeric/goffice.

[Morten Welinder <mortenw src gnome org>]

commit 2a41eaa225ca9f45716323eb13c977fa4e96dc64
Author: Morten Welinder <terra gnome org>
Date:   Fri Feb 15 19:08:09 2013 -0500

    Compilation: copy warning setup from gnumeric/goffice.
    
    That included hard error on missing prototype.

 configure.ac |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index ac5b419..dc784bb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -164,8 +164,17 @@ AC_SUBST(TYPELIBDIR)
 ifdef([GNOME_COMPILE_WARNINGS],[GNOME_COMPILE_WARNINGS],)
 CFLAGS="$CFLAGS $WARN_CFLAGS -DG_DISABLE_DEPRECATED"
 if test "$GCC" = "yes"; then
-       for option in -Wno-system-headers -Wfloat-equal -Wpointer-arith -Wbad-function-cast -Wwrite-strings 
-Wsign-compare -Waggregate-return -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wformat=2 
-Wnested-externs -Winline -Wdeclaration-after-statement -Wundef -W -Wmissing-noreturn 
-Wmissing-format-attribute -Wno-pointer-sign \
-       -Wbitwise -Wcast-to-as -Wdefault-bitfield-sign -Wdo-while -Wparen-string -Wptr-subtraction-blows 
-Wreturn-void -Wtypesign ; do
+       warning_options="-Wsign-compare -Wpointer-arith -Wnested-externs \
+                        -Wchar-subscripts -Wwrite-strings \
+                        -Wdeclaration-after-statement -Wnested-externs \
+                        -Wmissing-noreturn -Wmissing-prototypes \
+                        -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"
+       for option in $warning_options ; do
                SAVE_CFLAGS="$CFLAGS"
                CFLAGS="$CFLAGS $option"
                AC_MSG_CHECKING([whether gcc understands $option])