Update autotools filesv2.13

16 files changed, 272 insertions, 237 deletions

diff --git a/INSTALL b/INSTALL
index 2099840..8865734 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,8 +1,8 @@
 Installation Instructions
 *************************
 
-Copyright (C) 1994-1996, 1999-2002, 2004-2013 Free Software Foundation,
-Inc.
+   Copyright (C) 1994-1996, 1999-2002, 2004-2016 Free Software
+Foundation, Inc.
 
    Copying and distribution of this file, with or without modification,
 are permitted in any medium without royalty provided the copyright
@@ -12,97 +12,96 @@ without warranty of any kind.
 Basic Installation
 ==================
 
-   Briefly, the shell command `./configure && make && make install'
+   Briefly, the shell command './configure && make && make install'
 should configure, build, and install this package.  The following
-more-detailed instructions are generic; see the `README' file for
+more-detailed instructions are generic; see the 'README' file for
 instructions specific to this package.  Some packages provide this
-`INSTALL' file but do not implement all of the features documented
+'INSTALL' file but do not implement all of the features documented
 below.  The lack of an optional feature in a given package is not
 necessarily a bug.  More recommendations for GNU packages can be found
 in *note Makefile Conventions: (standards)Makefile Conventions.
 
-   The `configure' shell script attempts to guess correct values for
+   The 'configure' shell script attempts to guess correct values for
 various system-dependent variables used during compilation.  It uses
-those values to create a `Makefile' in each directory of the package.
-It may also create one or more `.h' files containing system-dependent
-definitions.  Finally, it creates a shell script `config.status' that
+those values to create a 'Makefile' in each directory of the package.
+It may also create one or more '.h' files containing system-dependent
+definitions.  Finally, it creates a shell script 'config.status' that
 you can run in the future to recreate the current configuration, and a
-file `config.log' containing compiler output (useful mainly for
-debugging `configure').
+file 'config.log' containing compiler output (useful mainly for
+debugging 'configure').
 
-   It can also use an optional file (typically called `config.cache'
-and enabled with `--cache-file=config.cache' or simply `-C') that saves
-the results of its tests to speed up reconfiguring.  Caching is
-disabled by default to prevent problems with accidental use of stale
-cache files.
+   It can also use an optional file (typically called 'config.cache' and
+enabled with '--cache-file=config.cache' or simply '-C') that saves the
+results of its tests to speed up reconfiguring.  Caching is disabled by
+default to prevent problems with accidental use of stale cache files.
 
    If you need to do unusual things to compile the package, please try
-to figure out how `configure' could check whether to do them, and mail
-diffs or instructions to the address given in the `README' so they can
+to figure out how 'configure' could check whether to do them, and mail
+diffs or instructions to the address given in the 'README' so they can
 be considered for the next release.  If you are using the cache, and at
-some point `config.cache' contains results you don't want to keep, you
+some point 'config.cache' contains results you don't want to keep, you
 may remove or edit it.
 
-   The file `configure.ac' (or `configure.in') is used to create
-`configure' by a program called `autoconf'.  You need `configure.ac' if
-you want to change it or regenerate `configure' using a newer version
-of `autoconf'.
+   The file 'configure.ac' (or 'configure.in') is used to create
+'configure' by a program called 'autoconf'.  You need 'configure.ac' if
+you want to change it or regenerate 'configure' using a newer version of
+'autoconf'.
 
    The simplest way to compile this package is:
 
-  1. `cd' to the directory containing the package's source code and type
-     `./configure' to configure the package for your system.
+  1. 'cd' to the directory containing the package's source code and type
+     './configure' to configure the package for your system.
 
-     Running `configure' might take a while.  While running, it prints
+     Running 'configure' might take a while.  While running, it prints
      some messages telling which features it is checking for.
 
-  2. Type `make' to compile the package.
+  2. Type 'make' to compile the package.
 
-  3. Optionally, type `make check' to run any self-tests that come with
+  3. Optionally, type 'make check' to run any self-tests that come with
      the package, generally using the just-built uninstalled binaries.
 
-  4. Type `make install' to install the programs and any data files and
+  4. Type 'make install' to install the programs and any data files and
      documentation.  When installing into a prefix owned by root, it is
      recommended that the package be configured and built as a regular
-     user, and only the `make install' phase executed with root
+     user, and only the 'make install' phase executed with root
      privileges.
 
-  5. Optionally, type `make installcheck' to repeat any self-tests, but
+  5. Optionally, type 'make installcheck' to repeat any self-tests, but
      this time using the binaries in their final installed location.
      This target does not install anything.  Running this target as a
-     regular user, particularly if the prior `make install' required
+     regular user, particularly if the prior 'make install' required
      root privileges, verifies that the installation completed
      correctly.
 
   6. You can remove the program binaries and object files from the
-     source code directory by typing `make clean'.  To also remove the
-     files that `configure' created (so you can compile the package for
-     a different kind of computer), type `make distclean'.  There is
-     also a `make maintainer-clean' target, but that is intended mainly
+     source code directory by typing 'make clean'.  To also remove the
+     files that 'configure' created (so you can compile the package for
+     a different kind of computer), type 'make distclean'.  There is
+     also a 'make maintainer-clean' target, but that is intended mainly
      for the package's developers.  If you use it, you may have to get
      all sorts of other programs in order to regenerate files that came
      with the distribution.
 
-  7. Often, you can also type `make uninstall' to remove the installed
+  7. Often, you can also type 'make uninstall' to remove the installed
      files again.  In practice, not all packages have tested that
      uninstallation works correctly, even though it is required by the
      GNU Coding Standards.
 
-  8. Some packages, particularly those that use Automake, provide `make
+  8. Some packages, particularly those that use Automake, provide 'make
      distcheck', which can by used by developers to test that all other
-     targets like `make install' and `make uninstall' work correctly.
+     targets like 'make install' and 'make uninstall' work correctly.
      This target is generally not run by end users.
 
 Compilers and Options
 =====================
 
    Some systems require unusual options for compilation or linking that
-the `configure' script does not know about.  Run `./configure --help'
+the 'configure' script does not know about.  Run './configure --help'
 for details on some of the pertinent environment variables.
 
-   You can give `configure' initial values for configuration parameters
-by setting variables in the command line or in the environment.  Here
-is an example:
+   You can give 'configure' initial values for configuration parameters
+by setting variables in the command line or in the environment.  Here is
+an example:
 
      ./configure CC=c99 CFLAGS=-g LIBS=-lposix
 
@@ -113,21 +112,21 @@ Compiling For Multiple Architectures
 
    You can compile the package for more than one kind of computer at the
 same time, by placing the object files for each architecture in their
-own directory.  To do this, you can use GNU `make'.  `cd' to the
+own directory.  To do this, you can use GNU 'make'.  'cd' to the
 directory where you want the object files and executables to go and run
-the `configure' script.  `configure' automatically checks for the
-source code in the directory that `configure' is in and in `..'.  This
-is known as a "VPATH" build.
+the 'configure' script.  'configure' automatically checks for the source
+code in the directory that 'configure' is in and in '..'.  This is known
+as a "VPATH" build.
 
-   With a non-GNU `make', it is safer to compile the package for one
+   With a non-GNU 'make', it is safer to compile the package for one
 architecture at a time in the source code directory.  After you have
-installed the package for one architecture, use `make distclean' before
+installed the package for one architecture, use 'make distclean' before
 reconfiguring for another architecture.
 
    On MacOS X 10.5 and later systems, you can create libraries and
 executables that work on multiple system types--known as "fat" or
-"universal" binaries--by specifying multiple `-arch' options to the
-compiler but only a single `-arch' option to the preprocessor.  Like
+"universal" binaries--by specifying multiple '-arch' options to the
+compiler but only a single '-arch' option to the preprocessor.  Like
 this:
 
      ./configure CC="gcc -arch i386 -arch x86_64 -arch ppc -arch ppc64" \
@@ -136,105 +135,104 @@ this:
 
    This is not guaranteed to produce working output in all cases, you
 may have to build one architecture at a time and combine the results
-using the `lipo' tool if you have problems.
+using the 'lipo' tool if you have problems.
 
 Installation Names
 ==================
 
-   By default, `make install' installs the package's commands under
-`/usr/local/bin', include files under `/usr/local/include', etc.  You
-can specify an installation prefix other than `/usr/local' by giving
-`configure' the option `--prefix=PREFIX', where PREFIX must be an
+   By default, 'make install' installs the package's commands under
+'/usr/local/bin', include files under '/usr/local/include', etc.  You
+can specify an installation prefix other than '/usr/local' by giving
+'configure' the option '--prefix=PREFIX', where PREFIX must be an
 absolute file name.
 
    You can specify separate installation prefixes for
 architecture-specific files and architecture-independent files.  If you
-pass the option `--exec-prefix=PREFIX' to `configure', the package uses
+pass the option '--exec-prefix=PREFIX' to 'configure', the package uses
 PREFIX as the prefix for installing programs and libraries.
 Documentation and other data files still use the regular prefix.
 
    In addition, if you use an unusual directory layout you can give
-options like `--bindir=DIR' to specify different values for particular
-kinds of files.  Run `configure --help' for a list of the directories
-you can set and what kinds of files go in them.  In general, the
-default for these options is expressed in terms of `${prefix}', so that
-specifying just `--prefix' will affect all of the other directory
+options like '--bindir=DIR' to specify different values for particular
+kinds of files.  Run 'configure --help' for a list of the directories
+you can set and what kinds of files go in them.  In general, the default
+for these options is expressed in terms of '${prefix}', so that
+specifying just '--prefix' will affect all of the other directory
 specifications that were not explicitly provided.
 
    The most portable way to affect installation locations is to pass the
-correct locations to `configure'; however, many packages provide one or
+correct locations to 'configure'; however, many packages provide one or
 both of the following shortcuts of passing variable assignments to the
-`make install' command line to change installation locations without
+'make install' command line to change installation locations without
 having to reconfigure or recompile.
 
    The first method involves providing an override variable for each
-affected directory.  For example, `make install
+affected directory.  For example, 'make install
 prefix=/alternate/directory' will choose an alternate location for all
 directory configuration variables that were expressed in terms of
-`${prefix}'.  Any directories that were specified during `configure',
-but not in terms of `${prefix}', must each be overridden at install
-time for the entire installation to be relocated.  The approach of
-makefile variable overrides for each directory variable is required by
-the GNU Coding Standards, and ideally causes no recompilation.
-However, some platforms have known limitations with the semantics of
-shared libraries that end up requiring recompilation when using this
-method, particularly noticeable in packages that use GNU Libtool.
-
-   The second method involves providing the `DESTDIR' variable.  For
-example, `make install DESTDIR=/alternate/directory' will prepend
-`/alternate/directory' before all installation names.  The approach of
-`DESTDIR' overrides is not required by the GNU Coding Standards, and
+'${prefix}'.  Any directories that were specified during 'configure',
+but not in terms of '${prefix}', must each be overridden at install time
+for the entire installation to be relocated.  The approach of makefile
+variable overrides for each directory variable is required by the GNU
+Coding Standards, and ideally causes no recompilation.  However, some
+platforms have known limitations with the semantics of shared libraries
+that end up requiring recompilation when using this method, particularly
+noticeable in packages that use GNU Libtool.
+
+   The second method involves providing the 'DESTDIR' variable.  For
+example, 'make install DESTDIR=/alternate/directory' will prepend
+'/alternate/directory' before all installation names.  The approach of
+'DESTDIR' overrides is not required by the GNU Coding Standards, and
 does not work on platforms that have drive letters.  On the other hand,
 it does better at avoiding recompilation issues, and works well even
-when some directory options were not specified in terms of `${prefix}'
-at `configure' time.
+when some directory options were not specified in terms of '${prefix}'
+at 'configure' time.
 
 Optional Features
 =================
 
    If the package supports it, you can cause programs to be installed
-with an extra prefix or suffix on their names by giving `configure' the
-option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.
-
-   Some packages pay attention to `--enable-FEATURE' options to
-`configure', where FEATURE indicates an optional part of the package.
-They may also pay attention to `--with-PACKAGE' options, where PACKAGE
-is something like `gnu-as' or `x' (for the X Window System).  The
-`README' should mention any `--enable-' and `--with-' options that the
+with an extra prefix or suffix on their names by giving 'configure' the
+option '--program-prefix=PREFIX' or '--program-suffix=SUFFIX'.
+
+   Some packages pay attention to '--enable-FEATURE' options to
+'configure', where FEATURE indicates an optional part of the package.
+They may also pay attention to '--with-PACKAGE' options, where PACKAGE
+is something like 'gnu-as' or 'x' (for the X Window System).  The
+'README' should mention any '--enable-' and '--with-' options that the
 package recognizes.
 
-   For packages that use the X Window System, `configure' can usually
+   For packages that use the X Window System, 'configure' can usually
 find the X include and library files automatically, but if it doesn't,
-you can use the `configure' options `--x-includes=DIR' and
-`--x-libraries=DIR' to specify their locations.
+you can use the 'configure' options '--x-includes=DIR' and
+'--x-libraries=DIR' to specify their locations.
 
    Some packages offer the ability to configure how verbose the
-execution of `make' will be.  For these packages, running `./configure
+execution of 'make' will be.  For these packages, running './configure
 --enable-silent-rules' sets the default to minimal output, which can be
-overridden with `make V=1'; while running `./configure
+overridden with 'make V=1'; while running './configure
 --disable-silent-rules' sets the default to verbose, which can be
-overridden with `make V=0'.
+overridden with 'make V=0'.
 
 Particular systems
 ==================
 
-   On HP-UX, the default C compiler is not ANSI C compatible.  If GNU
-CC is not installed, it is recommended to use the following options in
+   On HP-UX, the default C compiler is not ANSI C compatible.  If GNU CC
+is not installed, it is recommended to use the following options in
 order to use an ANSI C compiler:
 
      ./configure CC="cc -Ae -D_XOPEN_SOURCE=500"
 
 and if that doesn't work, install pre-built binaries of GCC for HP-UX.
 
-   HP-UX `make' updates targets which have the same time stamps as
-their prerequisites, which makes it generally unusable when shipped
-generated files such as `configure' are involved.  Use GNU `make'
-instead.
+   HP-UX 'make' updates targets which have the same time stamps as their
+prerequisites, which makes it generally unusable when shipped generated
+files such as 'configure' are involved.  Use GNU 'make' instead.
 
    On OSF/1 a.k.a. Tru64, some versions of the default C compiler cannot
-parse its `<wchar.h>' header file.  The option `-nodtk' can be used as
-a workaround.  If GNU CC is not installed, it is therefore recommended
-to try
+parse its '<wchar.h>' header file.  The option '-nodtk' can be used as a
+workaround.  If GNU CC is not installed, it is therefore recommended to
+try
 
      ./configure CC="cc"
 
@@ -242,26 +240,26 @@ and if that doesn't work, try
 
      ./configure CC="cc -nodtk"
 
-   On Solaris, don't put `/usr/ucb' early in your `PATH'.  This
+   On Solaris, don't put '/usr/ucb' early in your 'PATH'.  This
 directory contains several dysfunctional programs; working variants of
-these programs are available in `/usr/bin'.  So, if you need `/usr/ucb'
-in your `PATH', put it _after_ `/usr/bin'.
+these programs are available in '/usr/bin'.  So, if you need '/usr/ucb'
+in your 'PATH', put it _after_ '/usr/bin'.
 
-   On Haiku, software installed for all users goes in `/boot/common',
-not `/usr/local'.  It is recommended to use the following options:
+   On Haiku, software installed for all users goes in '/boot/common',
+not '/usr/local'.  It is recommended to use the following options:
 
      ./configure --prefix=/boot/common
 
 Specifying the System Type
 ==========================
 
-   There may be some features `configure' cannot figure out
+   There may be some features 'configure' cannot figure out
 automatically, but needs to determine by the type of machine the package
 will run on.  Usually, assuming the package is built to be run on the
-_same_ architectures, `configure' can figure that out, but if it prints
+_same_ architectures, 'configure' can figure that out, but if it prints
 a message saying it cannot guess the machine type, give it the
-`--build=TYPE' option.  TYPE can either be a short name for the system
-type, such as `sun4', or a canonical name which has the form:
+'--build=TYPE' option.  TYPE can either be a short name for the system
+type, such as 'sun4', or a canonical name which has the form:
 
      CPU-COMPANY-SYSTEM
 
@@ -270,101 +268,101 @@ where SYSTEM can have one of these forms:
      OS
      KERNEL-OS
 
-   See the file `config.sub' for the possible values of each field.  If
-`config.sub' isn't included in this package, then this package doesn't
+   See the file 'config.sub' for the possible values of each field.  If
+'config.sub' isn't included in this package, then this package doesn't
 need to know the machine type.
 
    If you are _building_ compiler tools for cross-compiling, you should
-use the option `--target=TYPE' to select the type of system they will
+use the option '--target=TYPE' to select the type of system they will
 produce code for.
 
    If you want to _use_ a cross compiler, that generates code for a
 platform different from the build platform, you should specify the
 "host" platform (i.e., that on which the generated programs will
-eventually be run) with `--host=TYPE'.
+eventually be run) with '--host=TYPE'.
 
 Sharing Defaults
 ================
 
-   If you want to set default values for `configure' scripts to share,
-you can create a site shell script called `config.site' that gives
-default values for variables like `CC', `cache_file', and `prefix'.
-`configure' looks for `PREFIX/share/config.site' if it exists, then
-`PREFIX/etc/config.site' if it exists.  Or, you can set the
-`CONFIG_SITE' environment variable to the location of the site script.
-A warning: not all `configure' scripts look for a site script.
+   If you want to set default values for 'configure' scripts to share,
+you can create a site shell script called 'config.site' that gives
+default values for variables like 'CC', 'cache_file', and 'prefix'.
+'configure' looks for 'PREFIX/share/config.site' if it exists, then
+'PREFIX/etc/config.site' if it exists.  Or, you can set the
+'CONFIG_SITE' environment variable to the location of the site script.
+A warning: not all 'configure' scripts look for a site script.
 
 Defining Variables
 ==================
 
    Variables not defined in a site shell script can be set in the
-environment passed to `configure'.  However, some packages may run
+environment passed to 'configure'.  However, some packages may run
 configure again during the build, and the customized values of these
 variables may be lost.  In order to avoid this problem, you should set
-them in the `configure' command line, using `VAR=value'.  For example:
+them in the 'configure' command line, using 'VAR=value'.  For example:
 
      ./configure CC=/usr/local2/bin/gcc
 
-causes the specified `gcc' to be used as the C compiler (unless it is
+causes the specified 'gcc' to be used as the C compiler (unless it is
 overridden in the site shell script).
 
-Unfortunately, this technique does not work for `CONFIG_SHELL' due to
-an Autoconf limitation.  Until the limitation is lifted, you can use
-this workaround:
+Unfortunately, this technique does not work for 'CONFIG_SHELL' due to an
+Autoconf limitation.  Until the limitation is lifted, you can use this
+workaround:
 
      CONFIG_SHELL=/bin/bash ./configure CONFIG_SHELL=/bin/bash
 
-`configure' Invocation
+'configure' Invocation
 ======================
 
-   `configure' recognizes the following options to control how it
+   'configure' recognizes the following options to control how it
 operates.
 
-`--help'
-`-h'
-     Print a summary of all of the options to `configure', and exit.
+'--help'
+'-h'
+     Print a summary of all of the options to 'configure', and exit.
 
-`--help=short'
-`--help=recursive'
+'--help=short'
+'--help=recursive'
      Print a summary of the options unique to this package's
-     `configure', and exit.  The `short' variant lists options used
-     only in the top level, while the `recursive' variant lists options
-     also present in any nested packages.
+     'configure', and exit.  The 'short' variant lists options used only
+     in the top level, while the 'recursive' variant lists options also
+     present in any nested packages.
 
-`--version'
-`-V'
-     Print the version of Autoconf used to generate the `configure'
+'--version'
+'-V'
+     Print the version of Autoconf used to generate the 'configure'
      script, and exit.
 
-`--cache-file=FILE'
+'--cache-file=FILE'
      Enable the cache: use and save the results of the tests in FILE,
-     traditionally `config.cache'.  FILE defaults to `/dev/null' to
+     traditionally 'config.cache'.  FILE defaults to '/dev/null' to
      disable caching.
 
-`--config-cache'
-`-C'
-     Alias for `--cache-file=config.cache'.
+'--config-cache'
+'-C'
+     Alias for '--cache-file=config.cache'.
 
-`--quiet'
-`--silent'
-`-q'
+'--quiet'
+'--silent'
+'-q'
      Do not print messages saying which checks are being made.  To
-     suppress all normal output, redirect it to `/dev/null' (any error
+     suppress all normal output, redirect it to '/dev/null' (any error
      messages will still be shown).
 
-`--srcdir=DIR'
+'--srcdir=DIR'
      Look for the package's source code in directory DIR.  Usually
-     `configure' can determine that directory automatically.
+     'configure' can determine that directory automatically.
 
-`--prefix=DIR'
-     Use DIR as the installation prefix.  *note Installation Names::
-     for more details, including other options available for fine-tuning
-     the installation locations.
+'--prefix=DIR'
+     Use DIR as the installation prefix.  *note Installation Names:: for
+     more details, including other options available for fine-tuning the
+     installation locations.
 
-`--no-create'
-`-n'
+'--no-create'
+'-n'
      Run the configure checks, but stop before creating any output
      files.
 
-`configure' also accepts some other, not widely useful, options.  Run
-`configure --help' for more details.
+'configure' also accepts some other, not widely useful, options.  Run
+'configure --help' for more details.
diff --git a/m4/ax_append_compile_flags.m4 b/m4/ax_append_compile_flags.m4
index dc7b866..5b6f1af 100644
--- a/m4/ax_append_compile_flags.m4
+++ b/m4/ax_append_compile_flags.m4
@@ -1,10 +1,10 @@
-# ===========================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_append_compile_flags.html
-# ===========================================================================
+# ============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_append_compile_flags.html
+# ============================================================================
 #
 # SYNOPSIS
 #
-#   AX_APPEND_COMPILE_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS])
+#   AX_APPEND_COMPILE_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS], [INPUT])
 #
 # DESCRIPTION
 #
@@ -20,6 +20,8 @@
 #   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: This macro depends on the AX_APPEND_FLAG and
 #   AX_CHECK_COMPILE_FLAG. Please keep this macro in sync with
 #   AX_APPEND_LINK_FLAGS.
@@ -39,7 +41,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -54,12 +56,12 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 4
+#serial 6
 
 AC_DEFUN([AX_APPEND_COMPILE_FLAGS],
 [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])], [], [$3])
+  AX_CHECK_COMPILE_FLAG([$flag], [AX_APPEND_FLAG([$flag], [$2])], [], [$3], [$4])
 done
 ])dnl AX_APPEND_COMPILE_FLAGS
diff --git a/m4/ax_append_flag.m4 b/m4/ax_append_flag.m4
index aeab899..e8c5312 100644
--- a/m4/ax_append_flag.m4
+++ b/m4/ax_append_flag.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#      http://www.gnu.org/software/autoconf-archive/ax_append_flag.html
+#      https://www.gnu.org/software/autoconf-archive/ax_append_flag.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -34,7 +34,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -49,7 +49,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 5
+#serial 7
 
 AC_DEFUN([AX_APPEND_FLAG],
 [dnl
@@ -59,7 +59,7 @@ AS_VAR_SET_IF(FLAGS,[
   AS_CASE([" AS_VAR_GET(FLAGS) "],
     [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
     [
-     AS_VAR_APPEND(FLAGS," $1")
+     AS_VAR_APPEND(FLAGS,[" $1"])
      AC_RUN_LOG([: FLAGS="$FLAGS"])
     ])
   ],
diff --git a/m4/ax_append_link_flags.m4 b/m4/ax_append_link_flags.m4
index c73ddaf..6f7f174 100644
--- a/m4/ax_append_link_flags.m4
+++ b/m4/ax_append_link_flags.m4
@@ -1,10 +1,10 @@
 # ===========================================================================
-#   http://www.gnu.org/software/autoconf-archive/ax_append_link_flags.html
+#   https://www.gnu.org/software/autoconf-archive/ax_append_link_flags.html
 # ===========================================================================
 #
 # SYNOPSIS
 #
-#   AX_APPEND_LINK_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS])
+#   AX_APPEND_LINK_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [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_COMPILE_IFELSE.
+#
 #   NOTE: This macro depends on the AX_APPEND_FLAG and AX_CHECK_LINK_FLAG.
 #   Please keep this macro in sync with AX_APPEND_COMPILE_FLAGS.
 #
@@ -37,7 +39,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -52,12 +54,12 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 4
+#serial 6
 
 AC_DEFUN([AX_APPEND_LINK_FLAGS],
 [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])])], [], [$3])
+  AX_CHECK_LINK_FLAG([$flag], [AX_APPEND_FLAG([$flag], [m4_default([$2], [LDFLAGS])])], [], [$3], [$4])
 done
 ])dnl AX_APPEND_LINK_FLAGS
diff --git a/m4/ax_cflags_force_c89.m4 b/m4/ax_cflags_force_c89.m4
index 1597b25..59b33c1 100644
--- a/m4/ax_cflags_force_c89.m4
+++ b/m4/ax_cflags_force_c89.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#    http://www.gnu.org/software/autoconf-archive/ax_cflags_force_c89.html
+#   https://www.gnu.org/software/autoconf-archive/ax_cflags_force_c89.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -40,7 +40,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -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 9
+#serial 10
 
 AC_DEFUN([AX_CFLAGS_FORCE_C89],[dnl
 AS_VAR_PUSHDEF([FLAGS],[CFLAGS])dnl
diff --git a/m4/ax_cflags_no_writable_strings.m4 b/m4/ax_cflags_no_writable_strings.m4
index 2fb6f12..48831fa 100644
--- a/m4/ax_cflags_no_writable_strings.m4
+++ b/m4/ax_cflags_no_writable_strings.m4
@@ -1,6 +1,6 @@
-# =================================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_cflags_no_writable_strings.html
-# =================================================================================
+# ==================================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_cflags_no_writable_strings.html
+# ==================================================================================
 #
 # SYNOPSIS
 #
@@ -41,7 +41,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -56,7 +56,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 13
+#serial 14
 
 AC_DEFUN([AX_FLAGS_NO_WRITABLE_STRINGS],[dnl
 AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
diff --git a/m4/ax_cflags_strict_prototypes.m4 b/m4/ax_cflags_strict_prototypes.m4
index 3ad4bf0..1bc5db4 100644
--- a/m4/ax_cflags_strict_prototypes.m4
+++ b/m4/ax_cflags_strict_prototypes.m4
@@ -1,6 +1,6 @@
-# ===============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_cflags_strict_prototypes.html
-# ===============================================================================
+# ================================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_cflags_strict_prototypes.html
+# ================================================================================
 #
 # SYNOPSIS
 #
@@ -43,7 +43,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -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 13
+#serial 16
 
 AC_DEFUN([AX_FLAGS_STRICT_PROTOTYPES],[dnl
 AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
@@ -68,8 +68,8 @@ VAR,[VAR="no, unknown"
 ac_save_[]FLAGS="$[]FLAGS"
 for ac_arg dnl
 in "-pedantic -Werror % -fstrict-prototypes -Wstrict-prototypes" dnl   GCC
-   "-pedantic -Werror % -Wstrict-prototypes" dnl try to warn atleast
-   "-pedantic -Werror % -Wmissing-prototypes" dnl try to warn atleast
+   "-pedantic -Werror % -Wstrict-prototypes" dnl try to warn at least
+   "-pedantic -Werror % -Wmissing-prototypes" dnl try to warn at least
    "-pedantic -Werror % -Werror-implicit-function-declaration" dnl
    "-pedantic -Werror % -Wimplicit-function-declaration" dnl
    "-pedantic % -Wstrict-prototypes %% no, unsupported" dnl oops
diff --git a/m4/ax_cflags_warn_all.m4 b/m4/ax_cflags_warn_all.m4
index 1f07799..094577e 100644
--- a/m4/ax_cflags_warn_all.m4
+++ b/m4/ax_cflags_warn_all.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#    http://www.gnu.org/software/autoconf-archive/ax_cflags_warn_all.html
+#    https://www.gnu.org/software/autoconf-archive/ax_cflags_warn_all.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -43,7 +43,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -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 15
+#serial 16
 
 AC_DEFUN([AX_FLAGS_WARN_ALL],[dnl
 AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
index ca36397..dcabb92 100644
--- a/m4/ax_check_compile_flag.m4
+++ b/m4/ax_check_compile_flag.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#   http://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -40,7 +40,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -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 4
+#serial 5
 
 AC_DEFUN([AX_CHECK_COMPILE_FLAG],
 [AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
diff --git a/m4/ax_check_link_flag.m4 b/m4/ax_check_link_flag.m4
index eb01a6c..819409a 100644
--- a/m4/ax_check_link_flag.m4
+++ b/m4/ax_check_link_flag.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#    http://www.gnu.org/software/autoconf-archive/ax_check_link_flag.html
+#    https://www.gnu.org/software/autoconf-archive/ax_check_link_flag.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -40,7 +40,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -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 4
+#serial 5
 
 AC_DEFUN([AX_CHECK_LINK_FLAG],
 [AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
diff --git a/m4/ax_compiler_flags.m4 b/m4/ax_compiler_flags.m4
index c52ae7d..ddb0456 100644
--- a/m4/ax_compiler_flags.m4
+++ b/m4/ax_compiler_flags.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#     http://www.gnu.org/software/autoconf-archive/ax_compiler_flags.html
+#    https://www.gnu.org/software/autoconf-archive/ax_compiler_flags.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -101,7 +101,7 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 12
+#serial 14
 
 # _AX_COMPILER_FLAGS_LANG([LANGNAME])
 m4_defun([_AX_COMPILER_FLAGS_LANG],
@@ -138,7 +138,7 @@ AC_DEFUN([AX_COMPILER_FLAGS],[
                                  [Unconditionally make all compiler warnings non-fatal]),,
                   [enable_Werror=maybe])
 
-    # Return the user’s chosen warning level
+    # Return the user's chosen warning level
     AS_IF([test "$enable_Werror" = "no" -a \
                 "$enable_compile_warnings" = "error"],[
         enable_compile_warnings="yes"
diff --git a/m4/ax_compiler_flags_cflags.m4 b/m4/ax_compiler_flags_cflags.m4
index 295d7fe..aeb16e3 100644
--- a/m4/ax_compiler_flags_cflags.m4
+++ b/m4/ax_compiler_flags_cflags.m4
@@ -1,6 +1,6 @@
-# ============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cflags.html
-# ============================================================================
+# =============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cflags.html
+# =============================================================================
 #
 # SYNOPSIS
 #
@@ -25,15 +25,16 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 8
+#serial 14
 
 AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
+    AC_REQUIRE([AC_PROG_SED])
     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_define([ax_warn_cflags_variable],
               [m4_normalize(ifelse([$1],,[WARN_CFLAGS],[$1]))])
 
     AC_LANG_PUSH([C])
@@ -49,6 +50,13 @@ AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
         ax_compiler_flags_test=""
     ])
 
+    # Check that -Wno-suggest-attribute=format is supported
+    AX_CHECK_COMPILE_FLAG([-Wno-suggest-attribute=format],[
+        ax_compiler_no_suggest_attribute_flags="-Wno-suggest-attribute=format"
+    ],[
+        ax_compiler_no_suggest_attribute_flags=""
+    ])
+
     # Base flags
     AX_APPEND_COMPILE_FLAGS([ dnl
         -fno-strict-aliasing dnl
@@ -100,14 +108,14 @@ AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
     ])
     AS_IF([test "$ax_enable_compile_warnings" = "error"],[
         # "error" flags; -Werror has to be appended unconditionally because
-        # it’s not possible to test for
+        # 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
+            [$ax_compiler_no_suggest_attribute_flags] dnl
         ],ax_warn_cflags_variable,[$ax_compiler_flags_test])
     ])
 
@@ -119,7 +127,7 @@ AC_DEFUN([AX_COMPILER_FLAGS_CFLAGS],[
         AS_CASE([$flag],
                 [-Wno-*=*],[],
                 [-Wno-*],[
-                    AX_APPEND_COMPILE_FLAGS([-Wno-error=${flag:5}],
+                    AX_APPEND_COMPILE_FLAGS([-Wno-error=$(AS_ECHO([$flag]) | $SED 's/^-Wno-//')],
                                             ax_warn_cflags_variable,
                                             [$ax_compiler_flags_test])
                 ])
diff --git a/m4/ax_compiler_flags_cxxflags.m4 b/m4/ax_compiler_flags_cxxflags.m4
index b768cfa..3067d9b 100644
--- a/m4/ax_compiler_flags_cxxflags.m4
+++ b/m4/ax_compiler_flags_cxxflags.m4
@@ -1,6 +1,6 @@
-# ==============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cxxflags.html
-# ==============================================================================
+# ===============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_compiler_flags_cxxflags.html
+# ===============================================================================
 #
 # SYNOPSIS
 #
@@ -26,15 +26,16 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 4
+#serial 10
 
 AC_DEFUN([AX_COMPILER_FLAGS_CXXFLAGS],[
+    AC_REQUIRE([AC_PROG_SED])
     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_define([ax_warn_cxxflags_variable],
               [m4_normalize(ifelse([$1],,[WARN_CXXFLAGS],[$1]))])
 
     AC_LANG_PUSH([C++])
@@ -50,6 +51,13 @@ AC_DEFUN([AX_COMPILER_FLAGS_CXXFLAGS],[
         ax_compiler_flags_test=""
     ])
 
+    # Check that -Wno-suggest-attribute=format is supported
+    AX_CHECK_COMPILE_FLAG([-Wno-suggest-attribute=format],[
+        ax_compiler_no_suggest_attribute_flags="-Wno-suggest-attribute=format"
+    ],[
+        ax_compiler_no_suggest_attribute_flags=""
+    ])
+
     # Base flags
     AX_APPEND_COMPILE_FLAGS([ dnl
         -fno-strict-aliasing dnl
@@ -96,14 +104,14 @@ AC_DEFUN([AX_COMPILER_FLAGS_CXXFLAGS],[
     ])
     AS_IF([test "$ax_enable_compile_warnings" = "error"],[
         # "error" flags; -Werror has to be appended unconditionally because
-        # it’s not possible to test for
+        # 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
+            [$ax_compiler_no_suggest_attribute_flags] dnl
         ],ax_warn_cxxflags_variable,[$ax_compiler_flags_test])
     ])
 
@@ -115,7 +123,7 @@ AC_DEFUN([AX_COMPILER_FLAGS_CXXFLAGS],[
         AS_CASE([$flag],
                 [-Wno-*=*],[],
                 [-Wno-*],[
-                    AX_APPEND_COMPILE_FLAGS([-Wno-error=${flag:5}],
+                    AX_APPEND_COMPILE_FLAGS([-Wno-error=$(AS_ECHO([$flag]) | $SED 's/^-Wno-//')],
                                             ax_warn_cxxflags_variable,
                                             [$ax_compiler_flags_test])
                 ])
diff --git a/m4/ax_compiler_flags_gir.m4 b/m4/ax_compiler_flags_gir.m4
index 180f50d..5b4924a 100644
--- a/m4/ax_compiler_flags_gir.m4
+++ b/m4/ax_compiler_flags_gir.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#   http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_gir.html
+#  https://www.gnu.org/software/autoconf-archive/ax_compiler_flags_gir.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -26,13 +26,13 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 4
+#serial 6
 
 AC_DEFUN([AX_COMPILER_FLAGS_GIR],[
     AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 
     # Variable names
-    m4_define(ax_warn_scannerflags_variable,
+    m4_define([ax_warn_scannerflags_variable],
               [m4_normalize(ifelse([$1],,[WARN_SCANNERFLAGS],[$1]))])
 
     # Base flags
diff --git a/m4/ax_compiler_flags_ldflags.m4 b/m4/ax_compiler_flags_ldflags.m4
index f9077fc..842e329 100644
--- a/m4/ax_compiler_flags_ldflags.m4
+++ b/m4/ax_compiler_flags_ldflags.m4
@@ -1,6 +1,6 @@
-# =============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_compiler_flags_ldflags.html
-# =============================================================================
+# ==============================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_compiler_flags_ldflags.html
+# ==============================================================================
 #
 # SYNOPSIS
 #
@@ -25,15 +25,16 @@
 #   and this notice are preserved.  This file is offered as-is, without any
 #   warranty.
 
-#serial 3
+#serial 8
 
 AC_DEFUN([AX_COMPILER_FLAGS_LDFLAGS],[
-    AX_REQUIRE_DEFINED([AX_APPEND_COMPILE_FLAGS])
+    AX_REQUIRE_DEFINED([AX_APPEND_LINK_FLAGS])
     AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
     AX_REQUIRE_DEFINED([AX_CHECK_COMPILE_FLAG])
+    AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
 
     # Variable names
-    m4_define(ax_warn_ldflags_variable,
+    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
@@ -47,26 +48,42 @@ AC_DEFUN([AX_COMPILER_FLAGS_LDFLAGS],[
         ax_compiler_flags_test=""
     ])
 
+    # macOS linker does not have --as-needed
+    AX_CHECK_LINK_FLAG([-Wl,--no-as-needed], [
+        ax_compiler_flags_as_needed_option="-Wl,--no-as-needed"
+    ], [
+        ax_compiler_flags_as_needed_option=""
+    ])
+
+    # macOS linker speaks with a different accent
+    ax_compiler_flags_fatal_warnings_option=""
+    AX_CHECK_LINK_FLAG([-Wl,--fatal-warnings], [
+        ax_compiler_flags_fatal_warnings_option="-Wl,--fatal-warnings"
+    ])
+    AX_CHECK_LINK_FLAG([-Wl,-fatal_warnings], [
+        ax_compiler_flags_fatal_warnings_option="-Wl,-fatal_warnings"
+    ])
+
     # Base flags
-    AX_APPEND_COMPILE_FLAGS([ dnl
-        -Wl,--no-as-needed dnl
+    AX_APPEND_LINK_FLAGS([ dnl
+        $ax_compiler_flags_as_needed_option 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_APPEND_LINK_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
+        # 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_APPEND_LINK_FLAGS([ dnl
+            $ax_compiler_flags_fatal_warnings_option dnl
         ],ax_warn_ldflags_variable,[$ax_compiler_flags_test])
     ])
 
diff --git a/m4/ax_require_defined.m4 b/m4/ax_require_defined.m4
index cae1111..17c3eab 100644
--- a/m4/ax_require_defined.m4
+++ b/m4/ax_require_defined.m4
@@ -1,5 +1,5 @@
 # ===========================================================================
-#    http://www.gnu.org/software/autoconf-archive/ax_require_defined.html
+#    https://www.gnu.org/software/autoconf-archive/ax_require_defined.html
 # ===========================================================================
 #
 # SYNOPSIS
@@ -30,7 +30,7 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 1
+#serial 2
 
 AC_DEFUN([AX_REQUIRE_DEFINED], [dnl
   m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])])