warning: module to simplify adding compiler warnings

[Simon Josefsson]

I want to add some warning flags from configure, including -Werror.

Using CFLAGS doesn't seem to be a good idea (some autoconf tests stops
working), so how about something like this module?

It allows me to add to configure.ac this:

gl_WARN_ADD([-Wall])
gl_WARN_ADD([-Wpointer-arith])
gl_WARN_ADD([-Wstrict-prototypes])
gl_WARN_ADD([-Wno-pointer-sign])
gl_WARN_ADD([-Werror])

Or similar.

One todo-item would be: Define one AC_SUBST variable per warning flag,
so that I can customize exactly which variables to use inside
Makefile.am.  This can be added later if a patch materializes, and if
this really is a good idea.

/Simon


>From 88dac5949945b72bba1508f6569f5e5deb6222f1 Mon Sep 17 00:00:00 2001
From: Simon Josefsson <address@hidden>
Date: Mon, 10 Nov 2008 19:04:07 +0100
Subject: [PATCH] Add warnings module.

---
 ChangeLog        |    6 ++++++
 MODULES.html.sh  |    1 +
 m4/warnings.m4   |   32 ++++++++++++++++++++++++++++++++
 modules/warnings |   16 ++++++++++++++++
 4 files changed, 55 insertions(+), 0 deletions(-)
 create mode 100644 m4/warnings.m4
 create mode 100644 modules/warnings

diff --git a/ChangeLog b/ChangeLog
index a81aa77..54fe08e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2008-11-10  Simon Josefsson  <address@hidden>
+
+       * modules/warnings: New module.
+       * m4/warnings.m4: New file.
+       * MODULES.html.sh: Mention warnings module.
+
 2008-11-10  Eric Blake  <address@hidden>
 
        fdl.texi: revert accidental change to license
diff --git a/MODULES.html.sh b/MODULES.html.sh
index 5198f0d..d3e5c13 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -2972,6 +2972,7 @@ func_all_modules ()
   func_module relocatable-prog
   func_module relocatable-prog-wrapper
   func_module relocatable-script
+  func_module warnings
   func_end_table
 
   element="Support for building documentation"
diff --git a/m4/warnings.m4 b/m4/warnings.m4
new file mode 100644
index 0000000..c1ec209
--- /dev/null
+++ b/m4/warnings.m4
@@ -0,0 +1,32 @@
+# warnings.m4 serial 1
+dnl Copyright (C) 2008 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+
+# gl_WARN_INIT
+# Initializes WARN_CFLAGS variable.
+AC_DEFUN([gl_WARN_INIT],
+[
+  AC_ARG_VAR(WARN_CFLAGS, [C compiler warning flags])
+])
+
+# gl_WARN_ADD([parameter]) adds parameter to WARN_CFLAGS if compiler
+# supports it.  For example, use gl_WARN_ADD([-Werror]).
+AC_DEFUN([gl_WARN_ADD],
+[
+  AC_MSG_CHECKING([whether compiler handles $1])
+
+  save_CFLAGS="$CFLAGS"
+  CFLAGS="${CFLAGS} $1"
+  AC_COMPILE_IFELSE(AC_LANG_PROGRAM([]), foo=yes, foo=no)
+  CFLAGS="$save_CFLAGS"
+
+  AC_MSG_RESULT($foo)
+
+  if test "$foo" = "yes"; then
+    WARN_CFLAGS="$WARN_CFLAGS $1"
+  fi
+])
diff --git a/modules/warnings b/modules/warnings
new file mode 100644
index 0000000..c893900
--- /dev/null
+++ b/modules/warnings
@@ -0,0 +1,16 @@
+Description:
+Helper M4 functions for safely adding compiler warning parameters.
+
+Files:
+m4/warnings.m4
+
+Depends-on:
+
+configure.ac:
+gl_WARN_INIT
+
+License:
+LGPLv2+
+
+Maintainer:
+all
-- 
1.5.6.5