update autotool files

Fix up the recursive logic with the ax processing so we actually grab all
the ones we need.  We probably grab too many, but meh.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

14 files changed, 633 insertions, 36 deletions

diff --git a/m4/ax_append_compile_flags.m4 b/m4/ax_append_compile_flags.m4
index 1f8e708..dc7b866 100644
--- a/m4/ax_append_compile_flags.m4
+++ b/m4/ax_append_compile_flags.m4
@@ -54,11 +54,11 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 3
+#serial 4
 
 AC_DEFUN([AX_APPEND_COMPILE_FLAGS],
-[AC_REQUIRE([AX_CHECK_COMPILE_FLAG])
-AC_REQUIRE([AX_APPEND_FLAG])
+[AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 for flag in $1; do
   AX_CHECK_COMPILE_FLAG([$flag], [AX_APPEND_FLAG([$flag], [$2])], [], [$3])
 done
diff --git a/m4/ax_append_flag.m4 b/m4/ax_append_flag.m4
index 1d38b76..aeab899 100644
--- a/m4/ax_append_flag.m4
+++ b/m4/ax_append_flag.m4
@@ -49,21 +49,23 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 2
+#serial 5
 
 AC_DEFUN([AX_APPEND_FLAG],
-[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX
-AS_VAR_PUSHDEF([FLAGS], [m4_default($2,_AC_LANG_PREFIX[FLAGS])])dnl
-AS_VAR_SET_IF(FLAGS,
-  [case " AS_VAR_GET(FLAGS) " in
-    *" $1 "*)
-      AC_RUN_LOG([: FLAGS already contains $1])
-      ;;
-    *)
-      AC_RUN_LOG([: FLAGS="$FLAGS $1"])
-      AS_VAR_SET(FLAGS, ["AS_VAR_GET(FLAGS) $1"])
-      ;;
-   esac],
-  [AS_VAR_SET(FLAGS,["$1"])])
+[dnl
+AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_SET_IF
+AS_VAR_PUSHDEF([FLAGS], [m4_default($2,_AC_LANG_PREFIX[FLAGS])])
+AS_VAR_SET_IF(FLAGS,[
+  AS_CASE([" AS_VAR_GET(FLAGS) "],
+    [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
+    [
+     AS_VAR_APPEND(FLAGS," $1")
+     AC_RUN_LOG([: FLAGS="$FLAGS"])
+    ])
+  ],
+  [
+  AS_VAR_SET(FLAGS,[$1])
+  AC_RUN_LOG([: FLAGS="$FLAGS"])
+  ])
 AS_VAR_POPDEF([FLAGS])dnl
 ])dnl AX_APPEND_FLAG
diff --git a/m4/ax_append_link_flags.m4 b/m4/ax_append_link_flags.m4
index 48cbd4b..c73ddaf 100644
--- a/m4/ax_append_link_flags.m4
+++ b/m4/ax_append_link_flags.m4
@@ -52,11 +52,11 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 3
+#serial 4
 
 AC_DEFUN([AX_APPEND_LINK_FLAGS],
-[AC_REQUIRE([AX_CHECK_LINK_FLAG])
-AC_REQUIRE([AX_APPEND_FLAG])
+[AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 for flag in $1; do
   AX_CHECK_LINK_FLAG([$flag], [AX_APPEND_FLAG([$flag], [m4_default([$2], [LDFLAGS])])], [], [$3])
 done
diff --git a/m4/ax_cflags_force_c89.m4 b/m4/ax_cflags_force_c89.m4
index 19ada7f..1597b25 100644
--- a/m4/ax_cflags_force_c89.m4
+++ b/m4/ax_cflags_force_c89.m4
@@ -55,7 +55,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 8
+#serial 9
 
 AC_DEFUN([AX_CFLAGS_FORCE_C89],[dnl
 AS_VAR_PUSHDEF([FLAGS],[CFLAGS])dnl
@@ -83,7 +83,7 @@ done
  AC_LANG_RESTORE
 ])
 AS_VAR_POPDEF([FLAGS])dnl
-AC_REQUIRE([AX_APPEND_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 case ".$VAR" in
      .ok|.ok,*) m4_ifvaln($3,$3) ;;
    .|.no|.no,*) m4_default($4,[m4_ifval($2,[AX_APPEND_FLAG([$2], [$1])])]) ;;
diff --git a/m4/ax_cflags_strict_prototypes.m4 b/m4/ax_cflags_strict_prototypes.m4
index 2ac34be..3ad4bf0 100644
--- a/m4/ax_cflags_strict_prototypes.m4
+++ b/m4/ax_cflags_strict_prototypes.m4
@@ -58,7 +58,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 12
+#serial 13
 
 AC_DEFUN([AX_FLAGS_STRICT_PROTOTYPES],[dnl
 AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
@@ -96,7 +96,7 @@ esac
 FLAGS="$ac_save_[]FLAGS"
 ])
 AS_VAR_POPDEF([FLAGS])dnl
-AC_REQUIRE([AX_APPEND_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 case ".$VAR" in
      .ok|.ok,*) m4_ifvaln($3,$3) ;;
    .|.no|.no,*) m4_default($4,[m4_ifval($2,[AX_APPEND_FLAG([$2], [$1])])]) ;;
diff --git a/m4/ax_cflags_warn_all.m4 b/m4/ax_cflags_warn_all.m4
index 0fa3e18..1f07799 100644
--- a/m4/ax_cflags_warn_all.m4
+++ b/m4/ax_cflags_warn_all.m4
@@ -58,7 +58,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 14
+#serial 15
 
 AC_DEFUN([AX_FLAGS_WARN_ALL],[dnl
 AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
@@ -84,7 +84,7 @@ done
 FLAGS="$ac_save_[]FLAGS"
 ])
 AS_VAR_POPDEF([FLAGS])dnl
-AC_REQUIRE([AX_APPEND_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 case ".$VAR" in
      .ok|.ok,*) m4_ifvaln($3,$3) ;;
    .|.no|.no,*) m4_default($4,[m4_ifval($2,[AX_APPEND_FLAG([$2], [$1])])]) ;;
diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
index c3a8d69..ca36397 100644
--- a/m4/ax_check_compile_flag.m4
+++ b/m4/ax_check_compile_flag.m4
@@ -4,7 +4,7 @@
 #
 # SYNOPSIS
 #
-#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS])
+#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
 #
 # DESCRIPTION
 #
@@ -19,6 +19,8 @@
 #   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
 #   force the compiler to issue an error when a bad flag is given.
 #
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
 #   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
 #   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
 #
@@ -53,19 +55,19 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 2
+#serial 4
 
 AC_DEFUN([AX_CHECK_COMPILE_FLAG],
-[AC_PREREQ(2.59)dnl for _AC_LANG_PREFIX
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
 AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
 AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
   ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
   _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
     [AS_VAR_SET(CACHEVAR,[yes])],
     [AS_VAR_SET(CACHEVAR,[no])])
   _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
-AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes],
+AS_VAR_IF(CACHEVAR,yes,
   [m4_default([$2], :)],
   [m4_default([$3], :)])
 AS_VAR_POPDEF([CACHEVAR])dnl
diff --git a/m4/ax_check_link_flag.m4 b/m4/ax_check_link_flag.m4
index e2d0d36..eb01a6c 100644
--- a/m4/ax_check_link_flag.m4
+++ b/m4/ax_check_link_flag.m4
@@ -4,7 +4,7 @@
 #
 # SYNOPSIS
 #
-#   AX_CHECK_LINK_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS])
+#   AX_CHECK_LINK_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
 #
 # DESCRIPTION
 #
@@ -19,6 +19,8 @@
 #   EXTRA-FLAGS FLAG".  This can for example be used to force the linker to
 #   issue an error when a bad flag is given.
 #
+#   INPUT gives an alternative input source to AC_LINK_IFELSE.
+#
 #   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
 #   macro in sync with AX_CHECK_{PREPROC,COMPILE}_FLAG.
 #
@@ -53,18 +55,19 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 2
+#serial 4
 
 AC_DEFUN([AX_CHECK_LINK_FLAG],
-[AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_ldflags_$4_$1])dnl
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_ldflags_$4_$1])dnl
 AC_CACHE_CHECK([whether the linker accepts $1], CACHEVAR, [
   ax_check_save_flags=$LDFLAGS
   LDFLAGS="$LDFLAGS $4 $1"
-  AC_LINK_IFELSE([AC_LANG_PROGRAM()],
+  AC_LINK_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
     [AS_VAR_SET(CACHEVAR,[yes])],
     [AS_VAR_SET(CACHEVAR,[no])])
   LDFLAGS=$ax_check_save_flags])
-AS_IF([test x"AS_VAR_GET(CACHEVAR)" = xyes],
+AS_VAR_IF(CACHEVAR,yes,
   [m4_default([$2], :)],
   [m4_default([$3], :)])
 AS_VAR_POPDEF([CACHEVAR])dnl
diff --git a/m4/ax_compiler_flags.m4 b/m4/ax_compiler_flags.m4
new file mode 100644
index 0000000..c52ae7d
--- /dev/null
+++ b/m4/ax_compiler_flags.m4
@@ -0,0 +1,158 @@
+# ===========================================================================
+#     http://www.gnu.org/software/autoconf-archive/ax_compiler_flags.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPILER_FLAGS([CFLAGS-VARIABLE], [LDFLAGS-VARIABLE], [IS-RELEASE], [EXTRA-BASE-CFLAGS], [EXTRA-YES-CFLAGS], [UNUSED], [UNUSED], [UNUSED], [EXTRA-BASE-LDFLAGS], [EXTRA-YES-LDFLAGS], [UNUSED], [UNUSED], [UNUSED])
+#
+# DESCRIPTION
+#
+#   Check for the presence of an --enable-compile-warnings option to
+#   configure, defaulting to "error" in normal operation, or "yes" if
+#   IS-RELEASE is equal to "yes".  Return the value in the variable
+#   $ax_enable_compile_warnings.
+#
+#   Depending on the value of --enable-compile-warnings, different compiler
+#   warnings are checked to see if they work with the current compiler and,
+#   if so, are appended to CFLAGS-VARIABLE and LDFLAGS-VARIABLE.  This
+#   allows a consistent set of baseline compiler warnings to be used across
+#   a code base, irrespective of any warnings enabled locally by individual
+#   developers.  By standardising the warnings used by all developers of a
+#   project, the project can commit to a zero-warnings policy, using -Werror
+#   to prevent compilation if new warnings are introduced.  This makes
+#   catching bugs which are flagged by warnings a lot easier.
+#
+#   By providing a consistent --enable-compile-warnings argument across all
+#   projects using this macro, continuous integration systems can easily be
+#   configured the same for all projects.  Automated systems or build
+#   systems aimed at beginners may want to pass the --disable-Werror
+#   argument to unconditionally prevent warnings being fatal.
+#
+#   --enable-compile-warnings can take the values:
+#
+#    * no:      Base compiler warnings only; not even -Wall.
+#    * yes:     The above, plus a broad range of useful warnings.
+#    * error:   The above, plus -Werror so that all warnings are fatal.
+#               Use --disable-Werror to override this and disable fatal
+#               warnings.
+#
+#   The set of base and enabled flags can be augmented using the
+#   EXTRA-*-CFLAGS and EXTRA-*-LDFLAGS variables, which are tested and
+#   appended to the output variable if --enable-compile-warnings is not
+#   "no". Flags should not be disabled using these arguments, as the entire
+#   point of AX_COMPILER_FLAGS is to enforce a consistent set of useful
+#   compiler warnings on code, using warnings which have been chosen for low
+#   false positive rates.  If a compiler emits false positives for a
+#   warning, a #pragma should be used in the code to disable the warning
+#   locally. See:
+#
+#     https://gcc.gnu.org/onlinedocs/gcc-4.9.2/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas
+#
+#   The EXTRA-* variables should only be used to supply extra warning flags,
+#   and not general purpose compiler flags, as they are controlled by
+#   configure options such as --disable-Werror.
+#
+#   IS-RELEASE can be used to disable -Werror when making a release, which
+#   is useful for those hairy moments when you just want to get the release
+#   done as quickly as possible.  Set it to "yes" to disable -Werror. By
+#   default, it uses the value of $ax_is_release, so if you are using the
+#   AX_IS_RELEASE macro, there is no need to pass this parameter. For
+#   example:
+#
+#     AX_IS_RELEASE([git-directory])
+#     AX_COMPILER_FLAGS()
+#
+#   CFLAGS-VARIABLE defaults to WARN_CFLAGS, and LDFLAGS-VARIABLE defaults
+#   to WARN_LDFLAGS.  Both variables are AC_SUBST-ed by this macro, but must
+#   be manually added to the CFLAGS and LDFLAGS variables for each target in
+#   the code base.
+#
+#   If C++ language support is enabled with AC_PROG_CXX, which must occur
+#   before this macro in configure.ac, warning flags for the C++ compiler
+#   are AC_SUBST-ed as WARN_CXXFLAGS, and must be manually added to the
+#   CXXFLAGS variables for each target in the code base.  EXTRA-*-CFLAGS can
+#   be used to augment the base and enabled flags.
+#
+#   Warning flags for g-ir-scanner (from GObject Introspection) are
+#   AC_SUBST-ed as WARN_SCANNERFLAGS.  This variable must be manually added
+#   to the SCANNERFLAGS variable for each GIR target in the code base.  If
+#   extra g-ir-scanner flags need to be enabled, the AX_COMPILER_FLAGS_GIR
+#   macro must be invoked manually.
+#
+#   AX_COMPILER_FLAGS may add support for other tools in future, in addition
+#   to the compiler and linker.  No extra EXTRA-* variables will be added
+#   for those tools, and all extra support will still use the single
+#   --enable-compile-warnings configure option.  For finer grained control
+#   over the flags for individual tools, use AX_COMPILER_FLAGS_CFLAGS,
+#   AX_COMPILER_FLAGS_LDFLAGS and AX_COMPILER_FLAGS_* for new tools.
+#
+#   The UNUSED variables date from a previous version of this macro, and are
+#   automatically appended to the preceding non-UNUSED variable. They should
+#   be left empty in new uses of the macro.
+#
+# LICENSE
+#
+#   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
+#   Copyright (c) 2015 David King <amigadave@amigadave.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 12
+
+# _AX_COMPILER_FLAGS_LANG([LANGNAME])
+m4_defun([_AX_COMPILER_FLAGS_LANG],
+[m4_ifdef([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [],
+          [m4_define([_AX_COMPILER_FLAGS_LANG_]$1[_enabled], [])dnl
+           AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_]$1[FLAGS])])dnl
+])
+
+AC_DEFUN([AX_COMPILER_FLAGS],[
+    # C support is enabled by default.
+    _AX_COMPILER_FLAGS_LANG([C])
+    # Only enable C++ support if AC_PROG_CXX is called. The redefinition of
+    # AC_PROG_CXX is so that a fatal error is emitted if this macro is called
+    # before AC_PROG_CXX, which would otherwise cause no C++ warnings to be
+    # checked.
+    AC_PROVIDE_IFELSE([AC_PROG_CXX],
+                      [_AX_COMPILER_FLAGS_LANG([CXX])],
+                      [m4_define([AC_PROG_CXX], defn([AC_PROG_CXX])[_AX_COMPILER_FLAGS_LANG([CXX])])])
+    AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS_LDFLAGS])
+
+    # Default value for IS-RELEASE is $ax_is_release
+    ax_compiler_flags_is_release=m4_tolower(m4_normalize(ifelse([$3],,
+                                                                [$ax_is_release],
+                                                                [$3])))
+
+    AC_ARG_ENABLE([compile-warnings],
+                  AS_HELP_STRING([--enable-compile-warnings=@<:@no/yes/error@:>@],
+                                 [Enable compiler warnings and errors]),,
+                  [AS_IF([test "$ax_compiler_flags_is_release" = "yes"],
+                         [enable_compile_warnings="yes"],
+                         [enable_compile_warnings="error"])])
+    AC_ARG_ENABLE([Werror],
+                  AS_HELP_STRING([--disable-Werror],
+                                 [Unconditionally make all compiler warnings non-fatal]),,
+                  [enable_Werror=maybe])
+
+    # Return the user’s chosen warning level
+    AS_IF([test "$enable_Werror" = "no" -a \
+                "$enable_compile_warnings" = "error"],[
+        enable_compile_warnings="yes"
+    ])
+
+    ax_enable_compile_warnings=$enable_compile_warnings
+
+    AX_COMPILER_FLAGS_CFLAGS([$1],[$ax_compiler_flags_is_release],
+                             [$4],[$5 $6 $7 $8])
+    m4_ifdef([_AX_COMPILER_FLAGS_LANG_CXX_enabled],
+             [AX_COMPILER_FLAGS_CXXFLAGS([WARN_CXXFLAGS],
+                                         [$ax_compiler_flags_is_release],
+                                         [$4],[$5 $6 $7 $8])])
+    AX_COMPILER_FLAGS_LDFLAGS([$2],[$ax_compiler_flags_is_release],
+                              [$9],[$10 $11 $12 $13])
+    AX_COMPILER_FLAGS_GIR([WARN_SCANNERFLAGS],[$ax_compiler_flags_is_release])
+])dnl AX_COMPILER_FLAGS
diff --git a/m4/ax_compiler_flags_cflags.m4 b/m4/ax_compiler_flags_cflags.m4
new file mode 100644
index 0000000..295d7fe
--- /dev/null
+++ b/m4/ax_compiler_flags_cflags.m4
@@ -0,0 +1,132 @@
+# ============================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cflags.html
+# ============================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPILER_FLAGS_CFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
+#
+# DESCRIPTION
+#
+#   Add warning flags for the C compiler to VARIABLE, which defaults to
+#   WARN_CFLAGS.  VARIABLE is AC_SUBST-ed by this macro, but must be
+#   manually added to the CFLAGS variable for each target in the code base.
+#
+#   This macro depends on the environment set up by AX_COMPILER_FLAGS.
+#   Specifically, it uses the value of $ax_enable_compile_warnings to decide
+#   which flags to enable.
+#
+# LICENSE
+#
+#   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 8
+
+AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
+    AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
+    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+    AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+
+    # Variable names
+    m4_define(ax_warn_cflags_variable,
+              [m4_normalize(ifelse([$1],,[WARN_CFLAGS],[$1]))])
+
+    AC_LANG_PUSH([C])
+
+    # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
+    # flags, otherwise they are always appended to the warn_cflags variable, and
+    # Clang warns on them for every compilation unit.
+    # If this is passed to GCC, it will explode, so the flag must be enabled
+    # conditionally.
+    AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
+        ax_compiler_flags_test="-Werror=unknown-warning-option"
+    ],[
+        ax_compiler_flags_test=""
+    ])
+
+    # Base flags
+    AX_APPEND_COMPILE_FLAGS([ dnl
+        -fno-strict-aliasing dnl
+        $3 dnl
+    ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
+
+    AS_IF([test "$ax_enable_compile_warnings" != "no"],[
+        # "yes" flags
+        AX_APPEND_COMPILE_FLAGS([ dnl
+            -Wall dnl
+            -Wextra dnl
+            -Wundef dnl
+            -Wnested-externs dnl
+            -Wwrite-strings dnl
+            -Wpointer-arith dnl
+            -Wmissing-declarations dnl
+            -Wmissing-prototypes dnl
+            -Wstrict-prototypes dnl
+            -Wredundant-decls dnl
+            -Wno-unused-parameter dnl
+            -Wno-missing-field-initializers dnl
+            -Wdeclaration-after-statement dnl
+            -Wformat=2 dnl
+            -Wold-style-definition dnl
+            -Wcast-align dnl
+            -Wformat-nonliteral dnl
+            -Wformat-security dnl
+            -Wsign-compare dnl
+            -Wstrict-aliasing dnl
+            -Wshadow dnl
+            -Winline dnl
+            -Wpacked dnl
+            -Wmissing-format-attribute dnl
+            -Wmissing-noreturn dnl
+            -Winit-self dnl
+            -Wredundant-decls dnl
+            -Wmissing-include-dirs dnl
+            -Wunused-but-set-variable dnl
+            -Warray-bounds dnl
+            -Wimplicit-function-declaration dnl
+            -Wreturn-type dnl
+            -Wswitch-enum dnl
+            -Wswitch-default dnl
+            $4 dnl
+            $5 dnl
+            $6 dnl
+            $7 dnl
+        ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
+    ])
+    AS_IF([test "$ax_enable_compile_warnings" = "error"],[
+        # "error" flags; -Werror has to be appended unconditionally because
+        # it’s not possible to test for
+        #
+        # suggest-attribute=format is disabled because it gives too many false
+        # positives
+        AX_APPEND_FLAG([-Werror],ax_warn_cflags_variable)
+
+        AX_APPEND_COMPILE_FLAGS([ dnl
+            -Wno-suggest-attribute=format dnl
+        ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
+    ])
+
+    # In the flags below, when disabling specific flags, always add *both*
+    # -Wno-foo and -Wno-error=foo. This fixes the situation where (for example)
+    # we enable -Werror, disable a flag, and a build bot passes CFLAGS=-Wall,
+    # which effectively turns that flag back on again as an error.
+    for flag in $ax_warn_cflags_variable; do
+        AS_CASE([$flag],
+                [-Wno-*=*],[],
+                [-Wno-*],[
+                    AX_APPEND_COMPILE_FLAGS([-Wno-error=${flag:5}],
+                                            ax_warn_cflags_variable,
+                                            [$ax_compiler_flags_test])
+                ])
+    done
+
+    AC_LANG_POP([C])
+
+    # Substitute the variables
+    AC_SUBST(ax_warn_cflags_variable)
+])dnl AX_COMPILER_FLAGS
diff --git a/m4/ax_compiler_flags_cxxflags.m4 b/m4/ax_compiler_flags_cxxflags.m4
new file mode 100644
index 0000000..b768cfa
--- /dev/null
+++ b/m4/ax_compiler_flags_cxxflags.m4
@@ -0,0 +1,128 @@
+# ==============================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cxxflags.html
+# ==============================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPILER_FLAGS_CXXFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
+#
+# DESCRIPTION
+#
+#   Add warning flags for the C++ compiler to VARIABLE, which defaults to
+#   WARN_CXXFLAGS.  VARIABLE is AC_SUBST-ed by this macro, but must be
+#   manually added to the CXXFLAGS variable for each target in the code
+#   base.
+#
+#   This macro depends on the environment set up by AX_COMPILER_FLAGS.
+#   Specifically, it uses the value of $ax_enable_compile_warnings to decide
+#   which flags to enable.
+#
+# LICENSE
+#
+#   Copyright (c) 2015 David King <amigadave@amigadave.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 4
+
+AC_DEFUN([AX_COMPILER_FLAGS_CXXFLAGS],[
+    AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
+    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+    AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+
+    # Variable names
+    m4_define(ax_warn_cxxflags_variable,
+              [m4_normalize(ifelse([$1],,[WARN_CXXFLAGS],[$1]))])
+
+    AC_LANG_PUSH([C++])
+
+    # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
+    # flags, otherwise they are always appended to the warn_cxxflags variable,
+    # and Clang warns on them for every compilation unit.
+    # If this is passed to GCC, it will explode, so the flag must be enabled
+    # conditionally.
+    AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
+        ax_compiler_flags_test="-Werror=unknown-warning-option"
+    ],[
+        ax_compiler_flags_test=""
+    ])
+
+    # Base flags
+    AX_APPEND_COMPILE_FLAGS([ dnl
+        -fno-strict-aliasing dnl
+        $3 dnl
+    ],ax_warn_cxxflags_variable,[$ax_compiler_flags_test])
+
+    AS_IF([test "$ax_enable_compile_warnings" != "no"],[
+        # "yes" flags
+        AX_APPEND_COMPILE_FLAGS([ dnl
+            -Wall dnl
+            -Wextra dnl
+            -Wundef dnl
+            -Wwrite-strings dnl
+            -Wpointer-arith dnl
+            -Wmissing-declarations dnl
+            -Wredundant-decls dnl
+            -Wno-unused-parameter dnl
+            -Wno-missing-field-initializers dnl
+            -Wformat=2 dnl
+            -Wcast-align dnl
+            -Wformat-nonliteral dnl
+            -Wformat-security dnl
+            -Wsign-compare dnl
+            -Wstrict-aliasing dnl
+            -Wshadow dnl
+            -Winline dnl
+            -Wpacked dnl
+            -Wmissing-format-attribute dnl
+            -Wmissing-noreturn dnl
+            -Winit-self dnl
+            -Wredundant-decls dnl
+            -Wmissing-include-dirs dnl
+            -Wunused-but-set-variable dnl
+            -Warray-bounds dnl
+            -Wreturn-type dnl
+            -Wno-overloaded-virtual dnl
+            -Wswitch-enum dnl
+            -Wswitch-default dnl
+            $4 dnl
+            $5 dnl
+            $6 dnl
+            $7 dnl
+        ],ax_warn_cxxflags_variable,[$ax_compiler_flags_test])
+    ])
+    AS_IF([test "$ax_enable_compile_warnings" = "error"],[
+        # "error" flags; -Werror has to be appended unconditionally because
+        # it’s not possible to test for
+        #
+        # suggest-attribute=format is disabled because it gives too many false
+        # positives
+        AX_APPEND_FLAG([-Werror],ax_warn_cxxflags_variable)
+
+        AX_APPEND_COMPILE_FLAGS([ dnl
+            -Wno-suggest-attribute=format dnl
+        ],ax_warn_cxxflags_variable,[$ax_compiler_flags_test])
+    ])
+
+    # In the flags below, when disabling specific flags, always add *both*
+    # -Wno-foo and -Wno-error=foo. This fixes the situation where (for example)
+    # we enable -Werror, disable a flag, and a build bot passes CXXFLAGS=-Wall,
+    # which effectively turns that flag back on again as an error.
+    for flag in $ax_warn_cxxflags_variable; do
+        AS_CASE([$flag],
+                [-Wno-*=*],[],
+                [-Wno-*],[
+                    AX_APPEND_COMPILE_FLAGS([-Wno-error=${flag:5}],
+                                            ax_warn_cxxflags_variable,
+                                            [$ax_compiler_flags_test])
+                ])
+    done
+
+    AC_LANG_POP([C++])
+
+    # Substitute the variables
+    AC_SUBST(ax_warn_cxxflags_variable)
+])dnl AX_COMPILER_FLAGS_CXXFLAGS
diff --git a/m4/ax_compiler_flags_gir.m4 b/m4/ax_compiler_flags_gir.m4
new file mode 100644
index 0000000..180f50d
--- /dev/null
+++ b/m4/ax_compiler_flags_gir.m4
@@ -0,0 +1,60 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_gir.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPILER_FLAGS_GIR([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
+#
+# DESCRIPTION
+#
+#   Add warning flags for the g-ir-scanner (from GObject Introspection) to
+#   VARIABLE, which defaults to WARN_SCANNERFLAGS.  VARIABLE is AC_SUBST-ed
+#   by this macro, but must be manually added to the SCANNERFLAGS variable
+#   for each GIR target in the code base.
+#
+#   This macro depends on the environment set up by AX_COMPILER_FLAGS.
+#   Specifically, it uses the value of $ax_enable_compile_warnings to decide
+#   which flags to enable.
+#
+# LICENSE
+#
+#   Copyright (c) 2015 Philip Withnall <philip@tecnocode.co.uk>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 4
+
+AC_DEFUN([AX_COMPILER_FLAGS_GIR],[
+    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+
+    # Variable names
+    m4_define(ax_warn_scannerflags_variable,
+              [m4_normalize(ifelse([$1],,[WARN_SCANNERFLAGS],[$1]))])
+
+    # Base flags
+    AX_APPEND_FLAG([$3],ax_warn_scannerflags_variable)
+
+    AS_IF([test "$ax_enable_compile_warnings" != "no"],[
+        # "yes" flags
+        AX_APPEND_FLAG([ dnl
+            --warn-all dnl
+            $4 dnl
+            $5 dnl
+            $6 dnl
+            $7 dnl
+        ],ax_warn_scannerflags_variable)
+    ])
+    AS_IF([test "$ax_enable_compile_warnings" = "error"],[
+        # "error" flags
+        AX_APPEND_FLAG([ dnl
+            --warn-error dnl
+        ],ax_warn_scannerflags_variable)
+    ])
+
+    # Substitute the variables
+    AC_SUBST(ax_warn_scannerflags_variable)
+])dnl AX_COMPILER_FLAGS
diff --git a/m4/ax_compiler_flags_ldflags.m4 b/m4/ax_compiler_flags_ldflags.m4
new file mode 100644
index 0000000..f9077fc
--- /dev/null
+++ b/m4/ax_compiler_flags_ldflags.m4
@@ -0,0 +1,75 @@
+# =============================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_ldflags.html
+# =============================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPILER_FLAGS_LDFLAGS([VARIABLE], [IS-RELEASE], [EXTRA-BASE-FLAGS], [EXTRA-YES-FLAGS])
+#
+# DESCRIPTION
+#
+#   Add warning flags for the linker to VARIABLE, which defaults to
+#   WARN_LDFLAGS.  VARIABLE is AC_SUBST-ed by this macro, but must be
+#   manually added to the LDFLAGS variable for each target in the code base.
+#
+#   This macro depends on the environment set up by AX_COMPILER_FLAGS.
+#   Specifically, it uses the value of $ax_enable_compile_warnings to decide
+#   which flags to enable.
+#
+# LICENSE
+#
+#   Copyright (c) 2014, 2015 Philip Withnall <philip@tecnocode.co.uk>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 3
+
+AC_DEFUN([AX_COMPILER_FLAGS_LDFLAGS],[
+    AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
+    AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+    AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+
+    # Variable names
+    m4_define(ax_warn_ldflags_variable,
+              [m4_normalize(ifelse([$1],,[WARN_LDFLAGS],[$1]))])
+
+    # Always pass -Werror=unknown-warning-option to get Clang to fail on bad
+    # flags, otherwise they are always appended to the warn_ldflags variable,
+    # and Clang warns on them for every compilation unit.
+    # If this is passed to GCC, it will explode, so the flag must be enabled
+    # conditionally.
+    AX_CHECK_COMPILE_FLAG([-Werror=unknown-warning-option],[
+        ax_compiler_flags_test="-Werror=unknown-warning-option"
+    ],[
+        ax_compiler_flags_test=""
+    ])
+
+    # Base flags
+    AX_APPEND_COMPILE_FLAGS([ dnl
+        -Wl,--no-as-needed dnl
+        $3 dnl
+    ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
+
+    AS_IF([test "$ax_enable_compile_warnings" != "no"],[
+        # "yes" flags
+        AX_APPEND_COMPILE_FLAGS([$4 $5 $6 $7],
+                                ax_warn_ldflags_variable,
+                                [$ax_compiler_flags_test])
+    ])
+    AS_IF([test "$ax_enable_compile_warnings" = "error"],[
+        # "error" flags; -Werror has to be appended unconditionally because
+        # it’s not possible to test for
+        #
+        # suggest-attribute=format is disabled because it gives too many false
+        # positives
+        AX_APPEND_COMPILE_FLAGS([ dnl
+            -Wl,--fatal-warnings dnl
+        ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
+    ])
+
+    # Substitute the variables
+    AC_SUBST(ax_warn_ldflags_variable)
+])dnl AX_COMPILER_FLAGS
diff --git a/m4/ax_require_defined.m4 b/m4/ax_require_defined.m4
new file mode 100644
index 0000000..cae1111
--- /dev/null
+++ b/m4/ax_require_defined.m4
@@ -0,0 +1,37 @@
+# ===========================================================================
+#    http://www.gnu.org/software/autoconf-archive/ax_require_defined.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_REQUIRE_DEFINED(MACRO)
+#
+# DESCRIPTION
+#
+#   AX_REQUIRE_DEFINED is a simple helper for making sure other macros have
+#   been defined and thus are available for use.  This avoids random issues
+#   where a macro isn't expanded.  Instead the configure script emits a
+#   non-fatal:
+#
+#     ./configure: line 1673: AX_CFLAGS_WARN_ALL: command not found
+#
+#   It's like AC_REQUIRE except it doesn't expand the required macro.
+#
+#   Here's an example:
+#
+#     AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
+#
+# LICENSE
+#
+#   Copyright (c) 2014 Mike Frysinger <vapier@gentoo.org>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 1
+
+AC_DEFUN([AX_REQUIRE_DEFINED], [dnl
+  m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])])
+])dnl AX_REQUIRE_DEFINED