[network-manager-fortisslvpn/th/gtk-split-and-log-bgo771544: 9/25] build: use m4/compiler_options.m4 from NetworkManager

[Thomas Haller <thaller src gnome org>]

commit 53e374f1a03cc643be025da042ba7ed4bb511d5e
Author: Thomas Haller <thaller redhat com>
Date:   Fri Sep 16 00:22:59 2016 +0200

    build: use m4/compiler_options.m4 from NetworkManager
    
    NetworkManager's m4 files was tweaked for supporting clang and special
    compiler warnings we care about. It is considered to be an improvement
    over the existing macros. Use them.
    
    Also, m4/compiler_warnings.m4 was present but unused.

 configure.ac            |    2 +
 m4/compiler_options.m4  |  111 +++++++++++++++++++++++++++++++++++++++++++++++
 m4/compiler_warnings.m4 |   34 --------------
 3 files changed, 113 insertions(+), 34 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6ccfcbd..da87666 100644
--- a/configure.ac
+++ b/configure.ac
@@ -106,6 +106,8 @@ fi
 NM_VPN_SERVICE_DIR=`$PKG_CONFIG --define-variable prefix='\${prefix}' --variable vpnservicedir libnm`
 AC_SUBST(NM_VPN_SERVICE_DIR)
 
+NM_COMPILER_WARNINGS
+
 test x"$enable_absolute_paths" = x"yes" && NM_PLUGIN_DIR='$(libdir)/NetworkManager/'
 AC_SUBST(NM_PLUGIN_DIR)
 
diff --git a/m4/compiler_options.m4 b/m4/compiler_options.m4
new file mode 100644
index 0000000..fa11c52
--- /dev/null
+++ b/m4/compiler_options.m4
@@ -0,0 +1,111 @@
+AC_DEFUN([_NM_COMPILER_FLAG], [
+       CFLAGS_SAVED="$CFLAGS"
+       CFLAGS="$CFLAGS $GLIB_CFLAGS -Werror $1"
+       AC_MSG_CHECKING([whether $1 works as expected])
+
+       AC_COMPILE_IFELSE([AC_LANG_SOURCE([[]])], [
+               AC_COMPILE_IFELSE([AC_LANG_SOURCE([[$2]])], [
+                       AC_MSG_RESULT(yes)
+                       CFLAGS="$CFLAGS_SAVED"
+                       $3
+               ],[
+                       AC_MSG_RESULT(no)
+                       CFLAGS="$CFLAGS_SAVED"
+                       $4
+               ])
+       ],[
+               AC_MSG_RESULT(not supported)
+               CFLAGS="$CFLAGS_SAVED"
+       ])
+])
+
+dnl Check whether a particular compiler flag is supported,
+dnl add it to CFLAGS if it is
+AC_DEFUN([NM_COMPILER_FLAG], [
+        _NM_COMPILER_FLAG([$1], [], [
+               CFLAGS="$CFLAGS $1"
+               $2
+       ], [$3])
+])
+
+dnl Check whether a particular warning is not emitted with code provided,
+dnl disable it in CFLAGS if the check fails.
+AC_DEFUN([NM_COMPILER_WARNING], [
+        _NM_COMPILER_FLAG([-W$1], [$2], [CFLAGS="$CFLAGS -W$1"], [CFLAGS="$CFLAGS -Wno-$1"])
+])
+
+AC_DEFUN([NM_COMPILER_WARNINGS],
+[AC_ARG_ENABLE(more-warnings,
+       AS_HELP_STRING([--enable-more-warnings], [Possible values: no/yes/error]),
+       set_more_warnings="$enableval",set_more_warnings=yes)
+AC_MSG_CHECKING(for more warnings)
+if test "$GCC" = "yes" -a "$set_more_warnings" != "no"; then
+       AC_MSG_RESULT(yes)
+
+       dnl This is enabled in clang by default, makes little sense,
+       dnl and causes the build to abort with -Werror.
+       CFLAGS_SAVED="$CFLAGS"
+       CFLAGS="$CFLAGS -Qunused-arguments"
+       AC_COMPILE_IFELSE([AC_LANG_SOURCE([])], [], CFLAGS="$CFLAGS_SAVED")
+       unset CFLAGS_SAVED
+
+       dnl clang only warns about unknown warnings, unless
+       dnl called with "-Werror=unknown-warning-option"
+       dnl Test if the compiler supports that, and if it does
+       dnl attach it to the CFLAGS.
+       NM_COMPILER_WARNING([unknown-warning-option], [])
+
+       CFLAGS_MORE_WARNINGS="-Wall -std=gnu89"
+
+       if test "x$set_more_warnings" = xerror; then
+               CFLAGS_MORE_WARNINGS="$CFLAGS_MORE_WARNINGS -Werror"
+       fi
+
+       for option in -Wshadow -Wmissing-declarations -Wmissing-prototypes \
+                     -Wdeclaration-after-statement -Wformat-security \
+                     -Wfloat-equal -Wno-unused-parameter -Wno-sign-compare \
+                     -Wno-duplicate-decl-specifier \
+                     -Wstrict-prototypes \
+                     -Wno-unused-but-set-variable \
+                     -Wno-format-y2k \
+                     -Wundef -Wimplicit-function-declaration \
+                     -Wpointer-arith -Winit-self -Wformat-nonliteral \
+                     -Wmissing-include-dirs -Wno-pragmas; do
+               dnl GCC 4.4 does not warn when checking for -Wno-* flags 
(https://gcc.gnu.org/wiki/FAQ#wnowarning)
+                _NM_COMPILER_FLAG([$(printf '%s' "$option" | sed 's/^-Wno-/-W/')], [],
+                                 [CFLAGS_MORE_WARNINGS="$CFLAGS_MORE_WARNINGS $option"], [])
+       done
+       unset option
+
+       dnl Disable warnings triggered by known compiler problems
+
+       dnl https://bugzilla.gnome.org/show_bug.cgi?id=745821
+       NM_COMPILER_WARNING([unknown-attributes], [#include <glib.h>])
+
+       dnl https://bugzilla.gnome.org/show_bug.cgi?id=744473
+       NM_COMPILER_WARNING([typedef-redefinition], [#include <gio/gio.h>])
+
+       dnl https://llvm.org/bugs/show_bug.cgi?id=21614
+       NM_COMPILER_WARNING([array-bounds],
+               [#include <string.h>]
+               [void f () { strcmp ("something", "0"); }]
+       )
+
+       dnl https://llvm.org/bugs/show_bug.cgi?id=22949
+       NM_COMPILER_WARNING([parentheses-equality],
+               [#include <sys/wait.h>]
+               [void f () { if (WIFCONTINUED(0)) return; }]
+       )
+
+       dnl systemd-dhcp's log_internal macro and our handle_warn are sometimes
+       dnl used in void context,u sometimes in int. Makes clang unhappy.
+       NM_COMPILER_WARNING([unused-value],
+               [#define yolo ({ (666 + 666); })]
+               [int f () { int i = yolo; yolo; return i; }]
+       )
+
+       CFLAGS="$CFLAGS_MORE_WARNINGS $CFLAGS"
+else
+       AC_MSG_RESULT(no)
+fi
+])