From 82cd18107f5283054aa8bad27b7741eaf0cfea4c Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@tele2.at>
Date: Thu, 12 Apr 2018 05:41:09 +0200
Subject: [PATCH] Add more compiler warning flags

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
---
 Makefile.am    |  2 +-
 configure.ac   | 24 ++++++++++++++++++++++++
 m4/compiler.m4 | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 m4/compiler.m4

diff --git a/Makefile.am b/Makefile.am
index 5f3823a..7f4f197 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,7 +1,7 @@
 ACLOCAL_AMFLAGS = -I m4
 
 AM_CPPFLAGS = -D_GNU_SOURCE -I$(top_srcdir)/lib/include
-AM_CFLAGS = -std=c99 -pedantic -Wall -Wextra
+AM_CFLAGS = -std=c99 $(WARN_CFLAGS)
 
 sbin_PROGRAMS =
 noinst_LIBRARIES =
diff --git a/configure.ac b/configure.ac
index 2f16261..750141e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,6 +21,30 @@ AC_ARG_WITH([pygos],
 	[AM_CONDITIONAL([PYGOSCFG], [true])])
 
 
+UL_WARN_ADD([-Wall])
+UL_WARN_ADD([-Wextra])
+UL_WARN_ADD([-Wunused])
+UL_WARN_ADD([-Wmissing-prototypes])
+UL_WARN_ADD([-Wmissing-declarations])
+UL_WARN_ADD([-Wwrite-strings])
+UL_WARN_ADD([-Wjump-misses-init])
+UL_WARN_ADD([-Wuninitialized])
+UL_WARN_ADD([-Winit-self])
+UL_WARN_ADD([-Wlogical-op])
+UL_WARN_ADD([-Wunused-but-set-parameter])
+UL_WARN_ADD([-Wunused-but-set-variable])
+UL_WARN_ADD([-Wunused-parameter])
+UL_WARN_ADD([-Wunused-result])
+UL_WARN_ADD([-Wunused-variable])
+UL_WARN_ADD([-Wduplicated-cond])
+UL_WARN_ADD([-Wduplicated-branches])
+UL_WARN_ADD([-Wrestrict])
+UL_WARN_ADD([-Wnull-dereference])
+UL_WARN_ADD([-pedantic])
+
+AC_SUBST([WARN_CFLAGS])
+
+
 AC_CONFIG_HEADERS([lib/include/config.h])
 AC_DEFINE_DIR(SVCDIR, sysconfdir/init.d, [Startup service directory])
 AC_DEFINE_DIR(TEMPLATEDIR, datadir/init, [Service template directory])
diff --git a/m4/compiler.m4 b/m4/compiler.m4
new file mode 100644
index 0000000..058c73f
--- /dev/null
+++ b/m4/compiler.m4
@@ -0,0 +1,40 @@
+dnl Copyright (C) 2008-2011 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
+dnl -- derivated from coreutils m4/warnings.m4
+
+# UL_AS_VAR_APPEND(VAR, VALUE)
+# ----------------------------
+# Provide the functionality of AS_VAR_APPEND if Autoconf does not have it.
+m4_ifdef([AS_VAR_APPEND],
+[m4_copy([AS_VAR_APPEND], [UL_AS_VAR_APPEND])],
+[m4_define([UL_AS_VAR_APPEND],
+[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])
+
+# UL_ADD_WARN(COMPILER_OPTION [, VARNAME])
+# ------------------------
+# Adds parameter to WARN_CFLAGS (or to $VARNAME) if the compiler supports it.
+AC_DEFUN([UL_WARN_ADD], [
+  m4_define([warnvarname], m4_default([$2],WARN_CFLAGS))
+  AS_VAR_PUSHDEF([ul_Warn], [ul_cv_warn_$1])dnl
+  AC_CACHE_CHECK([whether compiler handles $1], m4_defn([ul_Warn]), [
+    # store AC_LANG_WERROR status, then turn it on
+    save_ac_[]_AC_LANG_ABBREV[]_werror_flag="${ac_[]_AC_LANG_ABBREV[]_werror_flag}"
+    AC_LANG_WERROR
+
+    ul_save_CPPFLAGS="$CPPFLAGS"
+    CPPFLAGS="-Werror ${CPPFLAGS} $1"
+    AC_PREPROC_IFELSE([AC_LANG_PROGRAM([])],
+                      [AS_VAR_SET(ul_Warn, [yes])],
+                      [AS_VAR_SET(ul_Warn, [no])])
+    # restore AC_LANG_WERROR
+    ac_[]_AC_LANG_ABBREV[]_werror_flag="${save_ac_[]_AC_LANG_ABBREV[]_werror_flag}"
+
+    CPPFLAGS="$ul_save_CPPFLAGS"
+  ])
+  AS_VAR_IF(ul_Warn, [yes], [UL_AS_VAR_APPEND(warnvarname, [" $1"])])
+])
+