[PATCH dbus 3/5] build: turn on all practical compiler warning flags

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Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
---
 .gitignore                  |   1 +
 Makefile.am                 |   2 +
 configure.ac                |   3 +
 m4/manywarnings.m4          | 276 ++++++++++++++++++++++++++++++++++++++++++++
 m4/virt-arg.m4              | 154 ++++++++++++++++++++++++
 m4/virt-compile-warnings.m4 | 225 ++++++++++++++++++++++++++++++++++++
 m4/warnings.m4              |  79 +++++++++++++
 src/Makefile.am             |   4 +-
 8 files changed, 743 insertions(+), 1 deletion(-)
 create mode 100644 m4/manywarnings.m4
 create mode 100644 m4/virt-arg.m4
 create mode 100644 m4/virt-compile-warnings.m4
 create mode 100644 m4/warnings.m4

diff --git a/.gitignore b/.gitignore
index 727877b..95b2271 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,6 +20,7 @@ vgcore.*
 /configure
 /libvirt-dbus-*.tar.gz
 /libvirt-dbus.spec
+/m4/aclocal\.m4
 /stamp-h1
 
 /data/session/org.libvirt.service
diff --git a/Makefile.am b/Makefile.am
index 065334f..d2c3fc5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,6 +1,8 @@
 
 SUBDIRS = data src test
 
+ACLOCAL_AMFLAGS = -I m4
+
 EXTRA_DIST = \
 	$(PACKAGE).spec \
 	$(PACKAGE).spec.in \
diff --git a/configure.ac b/configure.ac
index 4c654fa..4c96fbe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3,6 +3,7 @@ AC_INIT([libvirt-dbus], [0.0.1], [libvir-list@xxxxxxxxxx], [], [http://libvirt.o
 AC_CONFIG_SRCDIR(src/main.c)
 AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_HEADERS([config.h])
+AC_CONFIG_MACRO_DIR([m4])
 dnl Make automake keep quiet about wildcards & other GNUmake-isms
 AM_INIT_AUTOMAKE([foreign -Wno-portability])
 AC_CANONICAL_HOST
@@ -35,6 +36,8 @@ AM_PROG_CC_C_O
 PKG_CHECK_MODULES(LIBVIRT, libvirt >= $LIBVIRT_REQUIRED)
 PKG_CHECK_MODULES(SYSTEMD, libsystemd >= $SYSTEMD_REQUIRED)
 
+LIBVIRT_COMPILE_WARNINGS
+
 AC_ARG_WITH(dbus-services,
 		  [AC_HELP_STRING([--with-dbus-services=<dir>],
 		  [where D-BUS session services directory is])])
diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
new file mode 100644
index 0000000..0f06ade
--- /dev/null
+++ b/m4/manywarnings.m4
@@ -0,0 +1,276 @@
+# manywarnings.m4 serial 8
+dnl Copyright (C) 2008-2017 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_MANYWARN_COMPLEMENT(OUTVAR, LISTVAR, REMOVEVAR)
+# --------------------------------------------------
+# Copy LISTVAR to OUTVAR except for the entries in REMOVEVAR.
+# Elements separated by whitespace.  In set logic terms, the function
+# does OUTVAR = LISTVAR \ REMOVEVAR.
+AC_DEFUN([gl_MANYWARN_COMPLEMENT],
+[
+  gl_warn_set=
+  set x $2; shift
+  for gl_warn_item
+  do
+    case " $3 " in
+      *" $gl_warn_item "*)
+        ;;
+      *)
+        gl_warn_set="$gl_warn_set $gl_warn_item"
+        ;;
+    esac
+  done
+  $1=$gl_warn_set
+])
+
+# gl_MANYWARN_ALL_GCC(VARIABLE)
+# -----------------------------
+# Add all documented GCC warning parameters to variable VARIABLE.
+# Note that you need to test them using gl_WARN_ADD if you want to
+# make sure your gcc understands it.
+AC_DEFUN([gl_MANYWARN_ALL_GCC],
+[
+  dnl First, check for some issues that only occur when combining multiple
+  dnl gcc warning categories.
+  AC_REQUIRE([AC_PROG_CC])
+  if test -n "$GCC"; then
+
+    dnl Check if -W -Werror -Wno-missing-field-initializers is supported
+    dnl with the current $CC $CFLAGS $CPPFLAGS.
+    AC_MSG_CHECKING([whether -Wno-missing-field-initializers is supported])
+    AC_CACHE_VAL([gl_cv_cc_nomfi_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -W -Werror -Wno-missing-field-initializers"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_nomfi_supported=yes],
+        [gl_cv_cc_nomfi_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_nomfi_supported])
+
+    if test "$gl_cv_cc_nomfi_supported" = yes; then
+      dnl Now check whether -Wno-missing-field-initializers is needed
+      dnl for the { 0, } construct.
+      AC_MSG_CHECKING([whether -Wno-missing-field-initializers is needed])
+      AC_CACHE_VAL([gl_cv_cc_nomfi_needed], [
+        gl_save_CFLAGS="$CFLAGS"
+        CFLAGS="$CFLAGS -W -Werror"
+        AC_COMPILE_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[int f (void)
+               {
+                 typedef struct { int a; int b; } s_t;
+                 s_t s1 = { 0, };
+                 return s1.b;
+               }
+             ]],
+             [[]])],
+          [gl_cv_cc_nomfi_needed=no],
+          [gl_cv_cc_nomfi_needed=yes])
+        CFLAGS="$gl_save_CFLAGS"
+      ])
+      AC_MSG_RESULT([$gl_cv_cc_nomfi_needed])
+    fi
+
+    dnl Next, check if -Werror -Wuninitialized is useful with the
+    dnl user's choice of $CFLAGS; some versions of gcc warn that it
+    dnl has no effect if -O is not also used
+    AC_MSG_CHECKING([whether -Wuninitialized is supported])
+    AC_CACHE_VAL([gl_cv_cc_uninitialized_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -Werror -Wuninitialized"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_uninitialized_supported=yes],
+        [gl_cv_cc_uninitialized_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_uninitialized_supported])
+
+  fi
+
+  # List all gcc warning categories.
+  # To compare this list to your installed GCC's, run this Bash command:
+  #
+  # comm -3 \
+  #  <(sed -n 's/^  *\(-[^ ]*\) .*/\1/p' manywarnings.m4 | sort) \
+  #  <(gcc --help=warnings | sed -n 's/^  \(-[^ ]*\) .*/\1/p' | sort |
+  #      grep -v -x -f <(
+  #         awk '/^[^#]/ {print $1}' ../build-aux/gcc-warning.spec))
+
+  gl_manywarn_set=
+  for gl_manywarn_item in \
+    -fno-common \
+    -W \
+    -Wabi \
+    -Waddress \
+    -Waggressive-loop-optimizations \
+    -Wall \
+    -Wattributes \
+    -Wbad-function-cast \
+    -Wbool-compare \
+    -Wbuiltin-macro-redefined \
+    -Wcast-align \
+    -Wchar-subscripts \
+    -Wchkp \
+    -Wclobbered \
+    -Wcomment \
+    -Wcomments \
+    -Wcoverage-mismatch \
+    -Wcpp \
+    -Wdate-time \
+    -Wdeprecated \
+    -Wdeprecated-declarations \
+    -Wdesignated-init \
+    -Wdisabled-optimization \
+    -Wdiscarded-array-qualifiers \
+    -Wdiscarded-qualifiers \
+    -Wdiv-by-zero \
+    -Wdouble-promotion \
+    -Wduplicated-cond \
+    -Wempty-body \
+    -Wendif-labels \
+    -Wenum-compare \
+    -Wextra \
+    -Wformat-contains-nul \
+    -Wformat-extra-args \
+    -Wformat-nonliteral \
+    -Wformat-security \
+    -Wformat-signedness \
+    -Wformat-y2k \
+    -Wformat-zero-length \
+    -Wframe-address \
+    -Wfree-nonheap-object \
+    -Whsa \
+    -Wignored-attributes \
+    -Wignored-qualifiers \
+    -Wimplicit \
+    -Wimplicit-function-declaration \
+    -Wimplicit-int \
+    -Wincompatible-pointer-types \
+    -Winit-self \
+    -Winline \
+    -Wint-conversion \
+    -Wint-to-pointer-cast \
+    -Winvalid-memory-model \
+    -Winvalid-pch \
+    -Wjump-misses-init \
+    -Wlogical-not-parentheses \
+    -Wlogical-op \
+    -Wmain \
+    -Wmaybe-uninitialized \
+    -Wmemset-transposed-args \
+    -Wmisleading-indentation \
+    -Wmissing-braces \
+    -Wmissing-declarations \
+    -Wmissing-field-initializers \
+    -Wmissing-include-dirs \
+    -Wmissing-parameter-type \
+    -Wmissing-prototypes \
+    -Wmultichar \
+    -Wnarrowing \
+    -Wnested-externs \
+    -Wnonnull \
+    -Wnonnull-compare \
+    -Wnull-dereference \
+    -Wodr \
+    -Wold-style-declaration \
+    -Wold-style-definition \
+    -Wopenmp-simd \
+    -Woverflow \
+    -Woverlength-strings \
+    -Woverride-init \
+    -Wpacked \
+    -Wpacked-bitfield-compat \
+    -Wparentheses \
+    -Wpointer-arith \
+    -Wpointer-sign \
+    -Wpointer-to-int-cast \
+    -Wpragmas \
+    -Wreturn-local-addr \
+    -Wreturn-type \
+    -Wscalar-storage-order \
+    -Wsequence-point \
+    -Wshadow \
+    -Wshift-count-negative \
+    -Wshift-count-overflow \
+    -Wshift-negative-value \
+    -Wsizeof-array-argument \
+    -Wsizeof-pointer-memaccess \
+    -Wstack-protector \
+    -Wstrict-aliasing \
+    -Wstrict-overflow \
+    -Wstrict-prototypes \
+    -Wsuggest-attribute=const \
+    -Wsuggest-attribute=format \
+    -Wsuggest-attribute=noreturn \
+    -Wsuggest-attribute=pure \
+    -Wsuggest-final-methods \
+    -Wsuggest-final-types \
+    -Wswitch \
+    -Wswitch-bool \
+    -Wswitch-default \
+    -Wsync-nand \
+    -Wsystem-headers \
+    -Wtautological-compare \
+    -Wtrampolines \
+    -Wtrigraphs \
+    -Wtype-limits \
+    -Wuninitialized \
+    -Wunknown-pragmas \
+    -Wunsafe-loop-optimizations \
+    -Wunused \
+    -Wunused-but-set-parameter \
+    -Wunused-but-set-variable \
+    -Wunused-function \
+    -Wunused-label \
+    -Wunused-local-typedefs \
+    -Wunused-macros \
+    -Wunused-parameter \
+    -Wunused-result \
+    -Wunused-value \
+    -Wunused-variable \
+    -Wvarargs \
+    -Wvariadic-macros \
+    -Wvector-operation-performance \
+    -Wvla \
+    -Wvolatile-register-var \
+    -Wwrite-strings \
+    \
+    ; do
+    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
+  done
+
+  # gcc --help=warnings outputs an unusual form for these options; list
+  # them here so that the above 'comm' command doesn't report a false match.
+  gl_manywarn_set="$gl_manywarn_set -Warray-bounds=2"
+  gl_manywarn_set="$gl_manywarn_set -Wnormalized=nfc"
+  gl_manywarn_set="$gl_manywarn_set -Wshift-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wunused-const-variable=2"
+
+  # These are needed for older GCC versions.
+  if test -n "$GCC"; then
+    case `($CC --version) 2>/dev/null` in
+      'gcc (GCC) '[[0-3]].* | \
+      'gcc (GCC) '4.[[0-7]].*)
+        gl_manywarn_set="$gl_manywarn_set -fdiagnostics-show-option"
+        gl_manywarn_set="$gl_manywarn_set -funit-at-a-time"
+          ;;
+    esac
+  fi
+
+  # Disable specific options as needed.
+  if test "$gl_cv_cc_nomfi_needed" = yes; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-missing-field-initializers"
+  fi
+
+  if test "$gl_cv_cc_uninitialized_supported" = no; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-uninitialized"
+  fi
+
+  $1=$gl_manywarn_set
+])
diff --git a/m4/virt-arg.m4 b/m4/virt-arg.m4
new file mode 100644
index 0000000..d626d72
--- /dev/null
+++ b/m4/virt-arg.m4
@@ -0,0 +1,154 @@
+dnl
+dnl virt-arg.m4: Helper macros for adding configure arguments
+dnl
+dnl Copyright (C) 2012-2014 Red Hat, Inc.
+dnl
+dnl This library is free software; you can redistribute it and/or
+dnl modify it under the terms of the GNU Lesser General Public
+dnl License as published by the Free Software Foundation; either
+dnl version 2.1 of the License, or (at your option) any later version.
+dnl
+dnl This library is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+dnl Lesser General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU Lesser General Public
+dnl License along with this library.  If not, see
+dnl <http://www.gnu.org/licenses/>.
+dnl
+
+
+dnl
+dnl To be used instead of AC_ARG_WITH
+dnl
+dnl See LIBVIRT_ARG_WITH_FEATURE if the argument you're adding is going to
+dnl be used for switching a feature on and off.
+dnl
+dnl LIBVIRT_ARG_WITH([CHECK_NAME], [HELP_DESC], [DEFAULT_ACTION])
+dnl
+dnl      CHECK_NAME: Suffix/prefix used for variables/flags, in uppercase.
+dnl       HELP_DESC: Description that will appear in configure --help
+dnl  DEFAULT_ACTION: Default configure action
+dnl
+dnl LIBVIRT_ARG_WITH([PACKAGER], [Extra packager name], [no])
+dnl LIBVIRT_ARG_WITH([HTML_DIR], [path to base html directory], [$(datadir)/doc])
+dnl
+AC_DEFUN([LIBVIRT_ARG_WITH], [
+  m4_pushdef([check_name], [$1])
+  m4_pushdef([help_desc], [[$2]])
+  m4_pushdef([default_action], [$3])
+
+  m4_pushdef([check_name_lc], m4_tolower(check_name))
+  m4_pushdef([check_name_dash], m4_translit(check_name_lc, [_], [-]))
+
+  m4_pushdef([arg_var], [with-]check_name_dash)
+  m4_pushdef([with_var], [with_]check_name_lc)
+
+  m4_divert_text([DEFAULTS], [with_var][[=]][default_action])
+  AC_ARG_WITH([check_name_lc],
+              [AS_HELP_STRING([[--]arg_var],
+                              ]m4_dquote(help_desc)[[ @<:@default=]]m4_dquote(default_action)[[@:>@])])
+
+  m4_popdef([with_var])
+  m4_popdef([arg_var])
+
+  m4_popdef([check_name_dash])
+  m4_popdef([check_name_lc])
+
+  m4_popdef([default_action])
+  m4_popdef([help_desc])
+  m4_popdef([check_name])
+])
+
+dnl
+dnl To be used instead of AC_ARG_WITH
+dnl
+dnl The difference between LIBVIRT_ARG_WITH and this macro is that the former
+dnl is mostly an enhanced drop-in replacement for AC_ARG_WITH, whereas the
+dnl latter is tailored for adding an argument that is going to be used to
+dnl switch a feature on and off: as a consequence, it optionally supports
+dnl specifying the minimum version for libraries the feature depends on and
+dnl automatically builds a suitable description from the feature name.
+dnl
+dnl LIBVIRT_ARG_WITH_FEATURE([CHECK_NAME], [HELP_NAME], [DEFAULT_ACTION], [MIN_VERSION])
+dnl
+dnl      CHECK_NAME: Suffix/prefix used for variables/flags, in uppercase.
+dnl       HELP_NAME: Name that will appear in configure --help
+dnl  DEFAULT_ACTION: Default configure action
+dnl     MIN_VERSION: Specify minimal version that will be added to
+dnl                  configure --help (optional)
+dnl
+dnl LIBVIRT_ARG_WITH_FEATURE([SELINUX], [SeLinux], [check])
+dnl LIBVIRT_ARG_WITH_FEATURE([GLUSTERFS], [glusterfs], [check], [3.4.1])
+dnl
+AC_DEFUN([LIBVIRT_ARG_WITH_FEATURE], [
+  m4_pushdef([check_name], [$1])
+  m4_pushdef([help_name], [[$2]])
+  m4_pushdef([default_action], [$3])
+  m4_pushdef([min_version], [$4])
+
+  m4_pushdef([check_name_lc], m4_tolower(check_name))
+  m4_pushdef([check_name_dash], m4_translit(check_name_lc, [_], [-]))
+
+  m4_pushdef([arg_var], [with-]check_name_dash)
+  m4_pushdef([with_var], [with_]check_name_lc)
+
+  m4_pushdef([version_text], m4_ifnblank(min_version, [[ (>= ]]min_version[[)]]))
+
+  m4_divert_text([DEFAULTS], [with_var][[=]][default_action])
+  AC_ARG_WITH([check_name_lc],
+              [AS_HELP_STRING([[--]arg_var],
+                              [with ]]m4_dquote(help_name)m4_dquote(version_text)[[ support @<:@default=]]m4_dquote(default_action)[[@:>@])])
+
+  m4_popdef([version_text])
+
+  m4_popdef([with_var])
+  m4_popdef([arg_var])
+
+  m4_popdef([check_name_dash])
+  m4_popdef([check_name_lc])
+
+  m4_popdef([min_version])
+  m4_popdef([default_action])
+  m4_popdef([help_name])
+  m4_popdef([check_name])
+])
+
+dnl
+dnl To be used instead of AC_ARG_ENABLE
+dnl
+dnl LIBVIRT_ARG_ENABLE([CHECK_NAME], [HELP_DESC], [DEFAULT_ACTION])
+dnl
+dnl      CHECK_NAME: Suffix/prefix used for variables/flags, in uppercase.
+dnl       HELP_DESC: Description that will appear in configure --help
+dnl  DEFAULT_ACTION: Default configure action
+dnl
+dnl LIBVIRT_ARG_ENABLE([DEBUG], [enable debugging output], [yes])
+dnl
+AC_DEFUN([LIBVIRT_ARG_ENABLE], [
+  m4_pushdef([check_name], [$1])
+  m4_pushdef([help_desc], [[$2]])
+  m4_pushdef([default_action], [$3])
+
+  m4_pushdef([check_name_lc], m4_tolower(check_name))
+  m4_pushdef([check_name_dash], m4_translit(check_name_lc, [_], [-]))
+
+  m4_pushdef([arg_var], [enable-]check_name_dash)
+  m4_pushdef([enable_var], [enable_]check_name_lc)
+
+  m4_divert_text([DEFAULTS], [enable_var][[=]][default_action])
+  AC_ARG_ENABLE([check_name_lc],
+                [AS_HELP_STRING([[--]arg_var],
+                                ]m4_dquote(help_desc)[[ @<:@default=]]m4_dquote(default_action)[[@:>@])])
+
+  m4_popdef([enable_var])
+  m4_popdef([arg_var])
+
+  m4_popdef([check_name_dash])
+  m4_popdef([check_name_lc])
+
+  m4_popdef([default_action])
+  m4_popdef([help_desc])
+  m4_popdef([check_name])
+])
diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
new file mode 100644
index 0000000..4d96a0e
--- /dev/null
+++ b/m4/virt-compile-warnings.m4
@@ -0,0 +1,225 @@
+dnl
+dnl Enable all known GCC compiler warnings, except for those
+dnl we can't yet cope with
+dnl
+AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
+    dnl ******************************
+    dnl More compiler warnings
+    dnl ******************************
+
+    LIBVIRT_ARG_ENABLE([WERROR], [Use -Werror (if supported)], [check])
+    if test "$enable_werror" = "check"; then
+        if test -d $srcdir/.git; then
+            is_git_version=true
+            enable_werror=yes
+        else
+            enable_werror=no
+        fi
+    fi
+
+    # List of warnings that are not relevant / wanted
+
+    # Don't care about C++ compiler compat
+    dontwarn="$dontwarn -Wc++-compat"
+    dontwarn="$dontwarn -Wabi"
+    dontwarn="$dontwarn -Wdeprecated"
+    # Don't care about ancient C standard compat
+    dontwarn="$dontwarn -Wtraditional"
+    # Don't care about ancient C standard compat
+    dontwarn="$dontwarn -Wtraditional-conversion"
+    # Ignore warnings in /usr/include
+    dontwarn="$dontwarn -Wsystem-headers"
+    # Happy for compiler to add struct padding
+    dontwarn="$dontwarn -Wpadded"
+    # GCC very confused with -O2
+    dontwarn="$dontwarn -Wunreachable-code"
+    # Too many to deal with
+    dontwarn="$dontwarn -Wconversion"
+    # Too many to deal with
+    dontwarn="$dontwarn -Wsign-conversion"
+    # GNULIB gettext.h violates
+    dontwarn="$dontwarn -Wvla"
+    # Many GNULIB header violations
+    dontwarn="$dontwarn -Wundef"
+    # Need to allow bad cast for execve()
+    dontwarn="$dontwarn -Wcast-qual"
+    # We need to use long long in many places
+    dontwarn="$dontwarn -Wlong-long"
+    # We allow manual list of all enum cases without default:
+    dontwarn="$dontwarn -Wswitch-default"
+    # We allow optional default: instead of listing all enum values
+    dontwarn="$dontwarn -Wswitch-enum"
+    # Not a problem since we don't use -fstrict-overflow
+    dontwarn="$dontwarn -Wstrict-overflow"
+    # Not a problem since we don't use -funsafe-loop-optimizations
+    dontwarn="$dontwarn -Wunsafe-loop-optimizations"
+    # Gnulib's stat-time.h violates this
+    dontwarn="$dontwarn -Waggregate-return"
+    # gcc 4.4.6 complains this is C++ only; gcc 4.7.0 implies this from -Wall
+    dontwarn="$dontwarn -Wenum-compare"
+    # gcc 5.1 -Wformat-signedness mishandles enums, not ready for prime time
+    dontwarn="$dontwarn -Wformat-signedness"
+    # Several conditionals expand the same on both branches
+    # depending on the particular platform/architecture
+    dontwarn="$dontwarn -Wduplicated-branches"
+    # > This warning does not generally indicate that there is anything wrong
+    # > with your code; it merely indicates that GCC's optimizers are unable
+    # > to handle the code effectively.
+    # Source: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
+    dontwarn="$dontwarn -Wdisabled-optimization"
+
+    # gcc 4.2 treats attribute(format) as an implicit attribute(nonnull),
+    # which triggers spurious warnings for our usage
+    AC_CACHE_CHECK([whether the C compiler's -Wformat allows NULL strings],
+      [lv_cv_gcc_wformat_null_works], [
+      save_CFLAGS=$CFLAGS
+      CFLAGS='-Wunknown-pragmas -Werror -Wformat'
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+        #include <stddef.h>
+        static __attribute__ ((__format__ (__printf__, 1, 2))) int
+        foo (const char *fmt, ...) { return !fmt; }
+      ]], [[
+        return foo(NULL);
+      ]])],
+      [lv_cv_gcc_wformat_null_works=yes],
+      [lv_cv_gcc_wformat_null_works=no])
+      CFLAGS=$save_CFLAGS])
+
+    AC_CACHE_CHECK([whether gcc gives bogus warnings for -Wlogical-op],
+      [lv_cv_gcc_wlogical_op_equal_expr_broken], [
+        save_CFLAGS="$CFLAGS"
+        CFLAGS="-O2 -Wlogical-op -Werror"
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+          #define TEST1 1
+          #define TEST2 TEST1
+        ]], [[
+          int test = 0;
+          return test == TEST1 || test == TEST2;]])],
+        [lv_cv_gcc_wlogical_op_equal_expr_broken=no],
+        [lv_cv_gcc_wlogical_op_equal_expr_broken=yes])
+        CFLAGS="$save_CFLAGS"])
+
+    AC_CACHE_CHECK([whether clang gives bogus warnings for -Wdouble-promotion],
+      [lv_cv_clang_double_promotion_broken], [
+        save_CFLAGS="$CFLAGS"
+        CFLAGS="-O2 -Wdouble-promotion -Werror"
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+          #include <math.h>
+        ]], [[
+          float f = 0.0;
+	  return isnan(f);]])],
+        [lv_cv_clang_double_promotion_broken=no],
+        [lv_cv_clang_double_promotion_broken=yes])
+        CFLAGS="$save_CFLAGS"])
+
+    if test "$lv_cv_clang_double_promotion_broken" = "yes";
+    then
+      dontwarn="$dontwarn -Wdouble-promotion"
+    fi
+
+    # Get all possible GCC warnings
+    gl_MANYWARN_ALL_GCC([maybewarn])
+
+    # Remove the ones we don't want, blacklisted earlier
+    gl_MANYWARN_COMPLEMENT([wantwarn], [$maybewarn], [$dontwarn])
+
+    # GNULIB uses '-W' (aka -Wextra) which includes a bunch of stuff.
+    # Unfortunately, this means you can't simply use '-Wsign-compare'
+    # with gl_MANYWARN_COMPLEMENT
+    # So we have -W enabled, and then have to explicitly turn off...
+    wantwarn="$wantwarn -Wno-sign-compare"
+
+    # GNULIB expects this to be part of -Wc++-compat, but we turn
+    # that one off, so we need to manually enable this again
+    wantwarn="$wantwarn -Wjump-misses-init"
+
+    # GNULIB turns on -Wformat=2 which implies -Wformat-nonliteral,
+    # so we need to manually re-exclude it.  Also, older gcc 4.2
+    # added an implied ATTRIBUTE_NONNULL on any parameter marked
+    # ATTRIBUTE_FMT_PRINT, which causes -Wformat failure on our
+    # intentional use of virReportError(code, NULL).
+    wantwarn="$wantwarn -Wno-format-nonliteral"
+    if test $lv_cv_gcc_wformat_null_works = no; then
+      wantwarn="$wantwarn -Wno-format"
+    fi
+
+    # -Wformat enables this by default, and we should keep it,
+    # but need to rewrite various areas of code first
+    wantwarn="$wantwarn -Wno-format-truncation"
+
+    # This should be < 256 really. Currently we're down to 4096,
+    # but using 1024 bytes sized buffers (mostly for virStrerror)
+    # stops us from going down further
+    gl_WARN_ADD([-Wframe-larger-than=4096], [STRICT_FRAME_LIMIT_CFLAGS])
+    gl_WARN_ADD([-Wframe-larger-than=25600], [RELAXED_FRAME_LIMIT_CFLAGS])
+
+    # Extra special flags
+    dnl -fstack-protector stuff passes gl_WARN_ADD with gcc
+    dnl on Mingw32, but fails when actually used
+    case $host in
+       aarch64-*-*)
+       dnl "error: -fstack-protector not supported for this target [-Werror]"
+       ;;
+       *-*-linux*)
+       dnl Prefer -fstack-protector-strong if it's available.
+       dnl There doesn't seem to be great overhead in adding
+       dnl -fstack-protector-all instead of -fstack-protector.
+       dnl
+       dnl We also don't need ssp-buffer-size with -all or -strong,
+       dnl since functions are protected regardless of buffer size.
+       dnl wantwarn="$wantwarn --param=ssp-buffer-size=4"
+       wantwarn="$wantwarn -fstack-protector-strong"
+       ;;
+       *-*-freebsd*)
+       dnl FreeBSD ships old gcc 4.2.1 which doesn't handle
+       dnl -fstack-protector-all well
+       wantwarn="$wantwarn -fstack-protector"
+
+       wantwarn="$wantwarn -Wno-unused-command-line-argument"
+       ;;
+    esac
+    wantwarn="$wantwarn -fexceptions"
+    wantwarn="$wantwarn -fasynchronous-unwind-tables"
+
+    # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
+    # fire even without -O.
+    wantwarn="$wantwarn -fipa-pure-const"
+
+    if test "$enable_werror" = "yes"
+    then
+      wantwarn="$wantwarn -Werror"
+    fi
+
+    # Check for $CC support of each warning
+    for w in $wantwarn; do
+      gl_WARN_ADD([$w])
+    done
+
+    case $host in
+        *-*-linux*)
+        dnl Fall back to -fstack-protector-all if -strong is not available
+        case $WARN_CFLAGS in
+        *-fstack-protector-strong*)
+        ;;
+        *)
+            gl_WARN_ADD([-fstack-protector-all])
+        ;;
+        esac
+        ;;
+    esac
+
+    case $WARN_CFLAGS in
+        *-Wsuggest-attribute=format*)
+           AC_DEFINE([HAVE_SUGGEST_ATTRIBUTE_FORMAT], [1], [Whether -Wsuggest-attribute=format works])
+        ;;
+    esac
+
+    # Silence certain warnings in gnulib, and use improved glibc headers
+    AH_VERBATIM([FORTIFY_SOURCE],
+    [/* Enable compile-time and run-time bounds-checking, and some warnings,
+        without upsetting newer glibc. */
+     #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
+     # define _FORTIFY_SOURCE 2
+     #endif
+    ])
+])
diff --git a/m4/warnings.m4 b/m4/warnings.m4
new file mode 100644
index 0000000..e697174
--- /dev/null
+++ b/m4/warnings.m4
@@ -0,0 +1,79 @@
+# warnings.m4 serial 11
+dnl Copyright (C) 2008-2017 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_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], [gl_AS_VAR_APPEND])],
+[m4_define([gl_AS_VAR_APPEND],
+[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])
+
+
+# gl_COMPILER_OPTION_IF(OPTION, [IF-SUPPORTED], [IF-NOT-SUPPORTED],
+#                       [PROGRAM = AC_LANG_PROGRAM()])
+# -----------------------------------------------------------------
+# Check if the compiler supports OPTION when compiling PROGRAM.
+#
+# FIXME: gl_Warn must be used unquoted until we can assume Autoconf
+# 2.64 or newer.
+AC_DEFUN([gl_COMPILER_OPTION_IF],
+[AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
+AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
+AS_LITERAL_IF([$1],
+  [m4_pushdef([gl_Positive], m4_bpatsubst([$1], [^-Wno-], [-W]))],
+  [gl_positive="$1"
+case $gl_positive in
+  -Wno-*) gl_positive=-W`expr "X$gl_positive" : 'X-Wno-\(.*\)'` ;;
+esac
+m4_pushdef([gl_Positive], [$gl_positive])])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
+  gl_save_compiler_FLAGS="$gl_Flags"
+  gl_AS_VAR_APPEND(m4_defn([gl_Flags]),
+    [" $gl_unknown_warnings_are_errors ]m4_defn([gl_Positive])["])
+  AC_LINK_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([])])],
+                 [AS_VAR_SET(gl_Warn, [yes])],
+                 [AS_VAR_SET(gl_Warn, [no])])
+  gl_Flags="$gl_save_compiler_FLAGS"
+])
+AS_VAR_IF(gl_Warn, [yes], [$2], [$3])
+m4_popdef([gl_Positive])dnl
+AS_VAR_POPDEF([gl_Flags])dnl
+AS_VAR_POPDEF([gl_Warn])dnl
+])
+
+# gl_UNKNOWN_WARNINGS_ARE_ERRORS
+# ------------------------------
+# Clang doesn't complain about unknown warning options unless one also
+# specifies -Wunknown-warning-option -Werror.  Detect this.
+AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS],
+[gl_COMPILER_OPTION_IF([-Werror -Wunknown-warning-option],
+   [gl_unknown_warnings_are_errors='-Wunknown-warning-option -Werror'],
+   [gl_unknown_warnings_are_errors=])])
+
+# gl_WARN_ADD(OPTION, [VARIABLE = WARN_CFLAGS],
+#             [PROGRAM = AC_LANG_PROGRAM()])
+# ---------------------------------------------
+# Adds parameter to WARN_CFLAGS if the compiler supports it when
+# compiling PROGRAM.  For example, gl_WARN_ADD([-Wparentheses]).
+#
+# If VARIABLE is a variable name, AC_SUBST it.
+AC_DEFUN([gl_WARN_ADD],
+[AC_REQUIRE([gl_UNKNOWN_WARNINGS_ARE_ERRORS])
+gl_COMPILER_OPTION_IF([$1],
+  [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_CFLAGS]], [[$2]]), [" $1"])],
+  [],
+  [$3])
+m4_ifval([$2],
+         [AS_LITERAL_IF([$2], [AC_SUBST([$2])])],
+         [AC_SUBST([WARN_CFLAGS])])dnl
+])
+
+# Local Variables:
+# mode: autoconf
+# End:
diff --git a/src/Makefile.am b/src/Makefile.am
index 917c46d..17b4fe1 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -18,7 +18,9 @@ libvirt_dbus_SOURCES = $(DAEMON_SOURCES)
 
 libvirt_dbus_CFLAGS = \
 	$(SYSTEMD_CFLAGS) \
-	$(LIBVIRT_CFLAGS)
+	$(LIBVIRT_CFLAGS) \
+	$(WARN_CFLAGS) \
+	$(NULL)
 
 libvirt_dbus_LDFLAGS = \
 	$(SYSTEMD_LDFLAGS) \
-- 
2.13.6

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