diff --git a/ANNOUNCE b/ANNOUNCE
index edd7b9173..0131f942f 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -123,6 +123,15 @@ Version 1.6.0beta07 [January 25, 2012]
     compiler issues slightly different warnings from those issued by the
     current vesions of GCC. This eliminates those warnings by
     adding/removing casts and small code rewrites.
+  Updated configure.ac from autoupdate: added --enable-werror option.
+    Also some layout regularization and removal of introduced tab characters
+    (replaced with 3-character indentation).  Obsolete macros identified by
+    autoupdate have been removed; the replacements are all in 2.59 so
+    the pre-req hasn't been changed.  --enable-werror checks for support
+    for -Werror (or the given argument) in the compiler.  This mimics the
+    gcc configure option by allowing -Werror to be turned on safely; without
+    the option the tests written in configure itself fail compilation because
+    they cause compiler warnings.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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diff --git a/CHANGES b/CHANGES
index 45b17a8ce..673e58713 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3874,6 +3874,15 @@ Version 1.6.0beta07 [January 25, 2012]
     compiler issues slightly different warnings from those issued by the
     current vesions of GCC. This eliminates those warnings by
     adding/removing casts and small code rewrites.
+  Updated configure.ac from autoupdate: added --enable-werror option.
+    Also some layout regularization and removal of introduced tab characters
+    (replaced with 3-character indentation).  Obsolete macros identified by
+    autoupdate have been removed; the replacements are all in 2.59 so
+    the pre-req hasn't been changed.  --enable-werror checks for support
+    for -Werror (or the given argument) in the compiler.  This mimics the
+    gcc configure option by allowing -Werror to be turned on safely; without
+    the option the tests written in configure itself fail compilation because
+    they cause compiler warnings.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/Makefile.am b/Makefile.am
index d750598a7..d17050fc8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -94,6 +94,12 @@ CLEANFILES= *.tf? pngout.png libpng@PNGLIB_MAJOR@@PNGLIB_MINOR@.pc \
 MAINTAINERCLEANFILES = Makefile.in aclocal.m4 config.guess config.h.in \
 config.sub configure depcomp install-sh ltmain.sh missing
 
+# PNG_COPTS give extra options for the C compiler to be used on all compilation
+# steps (unless targe_CFLAGS is specified; that will take precedence over
+# AM_CFLAGS)
+PNG_COPTS = @PNG_COPTS@
+AM_CFLAGS = ${PNG_COPTS}
+
 # DFNCPP is normally just CPP - the C preprocessor - but on Solaris and maybe
 # other operating systems (NeXT?) the C preprocessor selected by configure
 # checks input tokens for validity - effectively it performs part of the ANSI-C
diff --git a/configure.ac b/configure.ac
index 18eab26e2..9ea27eac4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -14,11 +14,11 @@ dnl Makefile.am to upgrade the package name.
 dnl This is here to prevent earlier autoconf from being used, it
 dnl should not be necessary to regenerate configure if the time
 dnl stamps are correct
-AC_PREREQ(2.59)
+AC_PREREQ([2.59])
 
 dnl Version number stuff here:
 
-AC_INIT([libpng], [1.6.0beta07], [png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.0beta07], [png-mng-implement@lists.sourceforge.net])
 AM_INIT_AUTOMAKE
 dnl stop configure from automagically running automake
 AM_MAINTAINER_MODE
@@ -31,13 +31,13 @@ PNGLIB_RELEASE=0
 dnl End of version number stuff
 
 AC_CONFIG_SRCDIR([pngget.c])
-AM_CONFIG_HEADER(config.h)
+AC_CONFIG_HEADERS([config.h])
 
 # Checks for programs.
 AC_LANG([C])
 AC_PROG_CC
 AM_PROG_AS
-AC_PROG_LD
+LT_PATH_LD
 AC_PROG_CPP
 AC_CHECK_TOOL(SED, sed, :)
 AC_CHECK_TOOL(AWK, awk, :)
@@ -51,16 +51,18 @@ LT_INIT([win32-dll])
 # check this:
 AC_REQUIRE_CPP
 AC_MSG_CHECKING([for a C preprocessor that does not parse its input])
-AC_TRY_CPP([1.5.0 16BIT],
+AC_PREPROC_IFELSE([AC_LANG_SOURCE([[1.1.1 16BIT]])],
    [DFNCPP="$CPP"],
-   [DFNCPP=""
-   sav_CPP="$CPP"
-   for CPP in "${CC-cc} -E" "${CC-cc} -E -traditional-cpp" "/lib/cpp" "cpp"; do
-      AC_TRY_CPP([1.5.0 16BIT],
-         [DFNCPP="$CPP"]
-         [break],,)
-   done
-   CPP="$sav_CPP"])
+   [  DFNCPP=""
+      sav_CPP="$CPP"
+      for CPP in "${CC-cc} -E" "${CC-cc} -E -traditional-cpp" "/lib/cpp" "cpp"
+      do
+         AC_PREPROC_IFELSE([AC_LANG_SOURCE([[1.1.1 16BIT]])],
+            [DFNCPP="$CPP"]
+            [break],,)
+      done
+      CPP="$sav_CPP"
+   ])
 if test -n "$DFNCPP"; then
    AC_MSG_RESULT([$DFNCPP])
    AC_SUBST(DFNCPP)
@@ -68,6 +70,31 @@ else
    AC_MSG_FAILURE([not found], 1)
 fi
 
+# -Werror cannot be passed to GCC in CFLAGS because configure will fail (it
+# checks the compiler with a program that generates a warning), add the
+# following option to deal with this
+AC_ARG_VAR(PNG_COPTS,
+   [additional flags for the C compiler, use this for options that would]
+   [cause configure itself to fail])
+AC_ARG_ENABLE(werror,
+   AS_HELP_STRING([[[--enable-werror[=OPT]]]],
+      [Pass -Werror or the given argument to the compiler if it is supported]),
+   [test "$enable_werror" = "yes" && enable_werror="-Werror"
+    if test "$enable_werror" != "no"; then
+      sav_CFLAGS="$CFLAGS"
+      CFLAGS="$enable_werror $CFLAGS"
+      AC_MSG_CHECKING([if the compiler allows $enable_werror])
+      AC_COMPILE_IFELSE(
+         [AC_LANG_SOURCE([
+            [int main(int argc, char **argv){]
+            [return argv[argc-1][0];]
+            [}]])],
+         AC_MSG_RESULT(yes)
+         PNG_COPTS="$PNG_COPTS $enable_werror",
+         AC_MSG_RESULT(no))
+      CFLAGS="$sav_CFLAGS"
+    fi],)
+
 # Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS([malloc.h stdlib.h string.h strings.h])
@@ -80,16 +107,15 @@ AC_C_RESTRICT
 
 # Checks for library functions.
 AC_FUNC_STRTOD
-AC_CHECK_FUNCS([memset], , AC_ERROR([memset not found in libc]))
-AC_CHECK_FUNCS([pow], , AC_CHECK_LIB(m, pow, , AC_ERROR([cannot find pow])) )
+AC_CHECK_FUNCS([memset], , AC_MSG_ERROR(memset not found in libc))
+AC_CHECK_FUNCS([pow], , AC_CHECK_LIB(m, pow, , AC_MSG_ERROR(cannot find pow)) )
 AC_ARG_WITH(zlib-prefix,
-   AC_HELP_STRING([--with-zlib-prefix],
-                  [prefix that may have been used in installed zlib]),
-                  [ZPREFIX=${withval}],
-                  [ZPREFIX='z_'])
+   AS_HELP_STRING([[[--with-zlib-prefix]]],
+      [prefix that may have been used in installed zlib]),
+      [ZPREFIX=${withval}],
+      [ZPREFIX='z_'])
 AC_CHECK_LIB(z, zlibVersion, ,
-    AC_CHECK_LIB(z, ${ZPREFIX}zlibVersion, ,
-                 AC_ERROR([zlib not installed])))
+    AC_CHECK_LIB(z, ${ZPREFIX}zlibVersion, , AC_MSG_ERROR(zlib not installed)))
 
 # The following is for pngvalid, to ensure it catches FP errors even on
 # platforms that don't enable FP exceptions, the function appears in the math
@@ -157,26 +183,26 @@ AC_SUBST(PNGLIB_RELEASE)
 # Additional arguments (and substitutions)
 # Allow the pkg-config directory to be set
 AC_ARG_WITH(pkgconfigdir,
-	AC_HELP_STRING([--with-pkgconfigdir],
-	[Use the specified pkgconfig dir (default is libdir/pkgconfig)]),
-	[pkgconfigdir=${withval}],
-	[pkgconfigdir='${libdir}/pkgconfig'])
+   AS_HELP_STRING([[[--with-pkgconfigdir]]],
+      [Use the specified pkgconfig dir (default is libdir/pkgconfig)]),
+   [pkgconfigdir=${withval}],
+   [pkgconfigdir='${libdir}/pkgconfig'])
 
 AC_SUBST([pkgconfigdir])
-AC_MSG_NOTICE([pkgconfig directory is ${pkgconfigdir}])
+AC_MSG_NOTICE([[pkgconfig directory is ${pkgconfigdir}]])
 
 # Make the *-config binary config scripts optional
 AC_ARG_WITH(binconfigs,
-	AC_HELP_STRING([--with-binconfigs],
-		[Generate shell libpng-config scripts as well as pkg-config data]
-		[@<:@default=yes@:>@]),
-	[if test "${withval}" = no; then
-		binconfigs=
-		AC_MSG_NOTICE([libpng-config scripts will not be built])
-	else
-		binconfigs='${binconfigs}'
-	fi],
-	[binconfigs='${binconfigs}'])
+   AS_HELP_STRING([[[--with-binconfigs]]],
+      [Generate shell libpng-config scripts as well as pkg-config data]
+      [@<:@default=yes@:>@]),
+   [if test "${withval}" = no; then
+      binconfigs=
+      AC_MSG_NOTICE([[libpng-config scripts will not be built]])
+    else
+      binconfigs='${binconfigs}'
+    fi],
+   [binconfigs='${binconfigs}'])
 AC_SUBST([binconfigs])
 
 # Because GCC by default assembles code with an executable stack, even though it
@@ -185,16 +211,18 @@ AC_SUBST([binconfigs])
 AC_SUBST([AM_CCASFLAGS], [-Wa,--noexecstack])
 
 AC_ARG_ENABLE([arm-neon],
-	AC_HELP_STRING([--enable-arm-neon], [Enable ARM NEON optimizations]),
-	[if test "${enableval}" = yes; then
-		AC_DEFINE([PNG_ARM_NEON], [1], [Enable ARM NEON optimizations])
-		AC_DEFINE([PNG_ALIGNED_MEMORY_SUPPORTED], [1], [Align row buffers])
-	fi])
+   AS_HELP_STRING([[[--enable-arm-neon]]], [Enable ARM NEON optimizations]),
+   [if test "${enableval}" = "yes"; then
+      AC_DEFINE([PNG_ARM_NEON], [1], [Enable ARM NEON optimizations])
+      AC_DEFINE([PNG_ALIGNED_MEMORY_SUPPORTED], [1], [Align row buffers])
+    fi])
 AM_CONDITIONAL([PNG_ARM_NEON], [test "${enable_arm_neon:-no}" = yes])
 
+AC_MSG_NOTICE([[Extra options for compiler: $PNG_COPTS]])
+
 # Config files, substituting as above
 AC_CONFIG_FILES([Makefile libpng.pc:libpng.pc.in])
 AC_CONFIG_FILES([libpng-config:libpng-config.in],
-		[chmod +x libpng-config])
+   [chmod +x libpng-config])
 
 AC_OUTPUT