From c7a3146a6c9c62a4103ec341bceccdb3c96d4019 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Thu, 9 Mar 2017 12:34:22 +0000
Subject: [PATCH 06/26] configure: Enable many more warnings and add
 --enable-werror.

Using the gnulib manywarnings module, enable many more GCC warnings.

Add the ./configure --enable-werror flag so that these warnings can be
turned into hard errors.  Only upstream developers should use this, it
should not be used for downstream, distro and production builds, and
it must not be the default.

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 bootstrap            |  1 +
 common/Makefile.am   |  2 +-
 configure.ac         | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 icotool/Makefile.am  |  2 +-
 wrestool/Makefile.am |  2 +-
 5 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/bootstrap b/bootstrap
index dce9299..d7e4609 100755
--- a/bootstrap
+++ b/bootstrap
@@ -29,6 +29,7 @@ if $gnulib_tool --version >/dev/null 2>&1; then
         gettimeofday \
         lstat \
         malloc-gnu \
+        manywarnings \
         memchr \
         minmax \
         progname \
diff --git a/common/Makefile.am b/common/Makefile.am
index 82c6ea1..a5bea98 100644
--- a/common/Makefile.am
+++ b/common/Makefile.am
@@ -27,4 +27,4 @@ AM_CPPFLAGS = \
 	-I$(top_builddir)/lib \
 	-I$(top_srcdir)/lib
 
-AM_CFLAGS = -Wall
+AM_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
diff --git a/configure.ac b/configure.ac
index d4b74ae..760ac2c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,52 @@ m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 # Gnulib
 gl_INIT
 
+# --enable-werror option for developers.
+AC_ARG_ENABLE([werror],
+    [AS_HELP_STRING([--enable-werror],
+                    [turn GCC warnings into errors (for developers)])],
+    [case $enableval in
+     yes|no) ;;
+     *)      AC_MSG_ERROR([bad value $enableval for werror option]) ;;
+     esac
+     gcc_werror=$enableval],
+    [gcc_werror=no]
+)
+if test "$gcc_werror" = "yes"; then
+    gl_WARN_ADD([-Werror], [WERROR_CFLAGS])
+    AC_SUBST([WERROR_CFLAGS])
+fi
+
+# $nw is the list of warnings we want to *disable*.  The nw warnings
+# are complemented below.
+nw=
+nw="$nw -Wvla"                    # Allow variable length arrays.
+nw="$nw -Wsuggest-attribute=pure" # Don't suggest function attributes.
+nw="$nw -Wsuggest-attribute=const"
+nw="$nw -Wsuggest-attribute=format"
+nw="$nw -Wstrict-prototypes"      # Don't require prototypes for every function.
+nw="$nw -Wmissing-prototypes"
+nw="$nw -Wmissing-declarations"
+nw="$nw -Wpacked"                 # Don't warn about packed structs.
+nw="$nw -Wswitch-default"         # This warning is actively dangerous.
+nw="$nw -Wunused-macros"          # Don't warn about defined but unused macros.
+
+gl_MANYWARN_ALL_GCC([ws])
+gl_MANYWARN_COMPLEMENT([ws], [$ws], $[nw])
+for w in $ws; do
+    gl_WARN_ADD([$w])
+done
+
+# Normally we disable warnings in $nw above.  However $nw only
+# filters out exact matching warning strings from a list inside
+# gnulib (see m4/manywarnings.m4).  So we need to explicitly list a
+# few disabled warnings below.
+
+# Allow unused function parameters.
+gl_WARN_ADD([-Wno-unused-parameter])
+
+AC_SUBST([WARN_CFLAGS])
+
 # Gettext
 AM_GNU_GETTEXT([external])
 # AM_GNU_GETTEXT_VERSION(0.14.1)
diff --git a/icotool/Makefile.am b/icotool/Makefile.am
index bd27fc8..8c42c9e 100644
--- a/icotool/Makefile.am
+++ b/icotool/Makefile.am
@@ -28,4 +28,4 @@ AM_CPPFLAGS = \
   -I$(top_srcdir)/lib \
   -I$(top_srcdir)
 
-AM_CFLAGS = -Wall
+AM_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
diff --git a/wrestool/Makefile.am b/wrestool/Makefile.am
index e18b9c2..3b5f3d4 100644
--- a/wrestool/Makefile.am
+++ b/wrestool/Makefile.am
@@ -27,4 +27,4 @@ AM_CPPFLAGS = \
   -I$(top_srcdir) \
   -I$(srcdir)/../icotool
 
-AM_CFLAGS = -Wall
+AM_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
-- 
2.10.2