diff --git a/Makefile.am b/Makefile.am
index 19efc2a711cd7ccb7c7474f2bd860ba37de7ea0e..86cdbf963999a0b73474811af71459faa8496e1d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -40,50 +40,50 @@ TESTS = celt/tests/test_unit_types celt/tests/test_unit_mathops celt/tests/test_
 
 opus_demo_SOURCES = src/opus_demo.c
 
-opus_demo_LDADD = libopus.la -lm
+opus_demo_LDADD = libopus.la $(LIBM)
 
 repacketizer_demo_SOURCES = src/repacketizer_demo.c
 
-repacketizer_demo_LDADD = libopus.la -lm
+repacketizer_demo_LDADD = libopus.la $(LIBM)
 
 opus_compare_SOURCES = src/opus_compare.c
-opus_compare_LDADD = -lm
+opus_compare_LDADD = $(LIBM)
 
 tests_test_opus_api_SOURCES = tests/test_opus_api.c tests/test_opus_common.h
-tests_test_opus_api_LDADD = libopus.la -lm
+tests_test_opus_api_LDADD = libopus.la $(LIBM)
 
 tests_test_opus_encode_SOURCES = tests/test_opus_encode.c tests/test_opus_common.h
-tests_test_opus_encode_LDADD = libopus.la -lm
+tests_test_opus_encode_LDADD = libopus.la $(LIBM)
 
 tests_test_opus_decode_SOURCES = tests/test_opus_decode.c tests/test_opus_common.h
-tests_test_opus_decode_LDADD = libopus.la -lm
+tests_test_opus_decode_LDADD = libopus.la $(LIBM)
 
 tests_test_opus_padding_SOURCES = tests/test_opus_padding.c tests/test_opus_common.h
-tests_test_opus_padding_LDADD = libopus.la -lm
+tests_test_opus_padding_LDADD = libopus.la $(LIBM)
 
 celt_tests_test_unit_cwrs32_SOURCES = celt/tests/test_unit_cwrs32.c
-celt_tests_test_unit_cwrs32_LDADD = -lm
+celt_tests_test_unit_cwrs32_LDADD = $(LIBM)
 
 celt_tests_test_unit_dft_SOURCES = celt/tests/test_unit_dft.c
-celt_tests_test_unit_dft_LDADD = -lm
+celt_tests_test_unit_dft_LDADD = $(LIBM)
 
 celt_tests_test_unit_entropy_SOURCES = celt/tests/test_unit_entropy.c
-celt_tests_test_unit_entropy_LDADD = -lm
+celt_tests_test_unit_entropy_LDADD = $(LIBM)
 
 celt_tests_test_unit_laplace_SOURCES = celt/tests/test_unit_laplace.c
-celt_tests_test_unit_laplace_LDADD = -lm
+celt_tests_test_unit_laplace_LDADD = $(LIBM)
 
 celt_tests_test_unit_mathops_SOURCES = celt/tests/test_unit_mathops.c
-celt_tests_test_unit_mathops_LDADD = -lm
+celt_tests_test_unit_mathops_LDADD = $(LIBM)
 
 celt_tests_test_unit_mdct_SOURCES = celt/tests/test_unit_mdct.c
-celt_tests_test_unit_mdct_LDADD = -lm
+celt_tests_test_unit_mdct_LDADD = $(LIBM)
 
 celt_tests_test_unit_rotation_SOURCES = celt/tests/test_unit_rotation.c
-celt_tests_test_unit_rotation_LDADD = -lm
+celt_tests_test_unit_rotation_LDADD = $(LIBM)
 
 celt_tests_test_unit_types_SOURCES = celt/tests/test_unit_types.c
-celt_tests_test_unit_types_LDADD = -lm
+celt_tests_test_unit_types_LDADD = $(LIBM)
 endif
 
 if CUSTOM_MODES
@@ -91,7 +91,7 @@ pkginclude_HEADERS += include/opus_custom.h
 if EXTRA_PROGRAMS
 noinst_PROGRAMS += opus_custom_demo
 opus_custom_demo_SOURCES = celt/opus_custom_demo.c
-opus_custom_demo_LDADD = libopus.la -lm
+opus_custom_demo_LDADD = libopus.la $(LIBM)
 endif
 endif
 
diff --git a/configure.ac b/configure.ac
index 824d4429c221b286be5e4daa02031a325ff363a9..13d04b09471d9b30885554670d840aee5ca6b483 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,8 +41,12 @@ AC_PROG_CC_C99
 AC_C_CONST
 AC_C_INLINE
 
+AC_DEFINE([OPUS_BUILD], [], [This is a build of OPUS])
+
 #Use a hacked up version of autoconf's AC_C_RESTRICT because it's not
 #strong enough a test to detect old buggy versions of GCC (e.g. 2.95.3)
+#Note: Both this and the test for variable-size arrays below are also
+#      done by AC_PROG_CC_C99, but not thoroughly enough apparently.
 AC_CACHE_CHECK([for C/C++ restrict keyword], ac_cv_c_restrict,
   [ac_cv_c_restrict=no
    # The order here caters to the fact that C++ does not require restrict.
@@ -60,7 +64,8 @@ AC_CACHE_CHECK([for C/C++ restrict keyword], ac_cv_c_restrict,
      test "$ac_cv_c_restrict" != no && break
    done
   ])
- AH_VERBATIM([restrict],
+
+AH_VERBATIM([restrict],
 [/* Define to the equivalent of the C99 'restrict' keyword, or to
    nothing if this is not supported.  Do not define if restrict is
    supported directly.  */
@@ -74,43 +79,76 @@ AC_CACHE_CHECK([for C/C++ restrict keyword], ac_cv_c_restrict,
 # define _Restrict
 # define __restrict__
 #endif])
- case $ac_cv_c_restrict in
+
+case $ac_cv_c_restrict in
    restrict) ;;
    no) AC_DEFINE([restrict], []) ;;
    *)  AC_DEFINE_UNQUOTED([restrict], [$ac_cv_c_restrict]) ;;
- esac
-
-AC_DEFINE([OPUS_BUILD], [], [This is a build of OPUS])
+esac
 
 AC_MSG_CHECKING(for C99 variable-size arrays)
-AC_TRY_COMPILE( [], [static int x; char a[++x]; a[sizeof a - 1] = 0; int N; return a[0];],
-[has_var_arrays=yes;AC_DEFINE([VAR_ARRAYS], [], [Use C99 variable-size arrays])
-],
-has_var_arrays=no
-)
-AC_MSG_RESULT($has_var_arrays)
-
-AC_CHECK_HEADERS([alloca.h getopt.h])
-AC_MSG_CHECKING(for alloca)
-AC_TRY_COMPILE( [#include <alloca.h>], [
-int foo=10;
-int *array = alloca(foo);
-],
-[
-has_alloca=yes;
-if test x$has_var_arrays = "xno" ; then
-AC_DEFINE([USE_ALLOCA], [], [Make use of alloca])
-fi
-],
-has_alloca=no
-)
-AC_MSG_RESULT($has_alloca)
-
-AC_CHECK_FUNC(exp,[fp_libm_not_needed=yes;LIBM=],[fp_libm_not_needed=dunno])
-if test x"$fp_libm_not_needed" = xdunno; then
-  AC_CHECK_LIB([m], [exp], [LIBS="-lm $LIBS"; LIBM="-lm"],[LIBM=])
-fi
-AC_SUBST([LIBM])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
+                   [[static int x; char a[++x]; a[sizeof a - 1] = 0; int N; return a[0];]])],
+    [ has_var_arrays=yes
+      use_alloca="no (using var arrays)"
+      AC_DEFINE([VAR_ARRAYS], [1], [Use C99 variable-size arrays])
+    ],[
+      has_var_arrays=no
+    ])
+AC_MSG_RESULT([$has_var_arrays])
+
+AS_IF([test "$has_var_arrays" = "no"],
+  [
+   AC_CHECK_HEADERS([alloca.h])
+   AC_MSG_CHECKING(for alloca)
+   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <alloca.h>]],
+                                      [[int foo=10; int *array = alloca(foo);]])],
+     [ use_alloca=yes;
+       AC_DEFINE([USE_ALLOCA], [], [Make use of alloca])
+     ],[
+       use_alloca=no
+     ])
+   AC_MSG_RESULT([$use_alloca])
+  ])
+
+LT_LIB_M
+
+AC_ARG_ENABLE([fixed-point],
+    [AS_HELP_STRING([--enable-fixed-point],
+                    [compile without floating point (for machines without a fast enough FPU)])],,
+    [enable_fixed_point=no])
+
+AS_IF([test "$enable_fixed_point" = "yes"],[
+  enable_float="no"
+  AC_DEFINE([FIXED_POINT], [1], [Compile as fixed-point (for machines without a fast enough FPU)])
+  PC_BUILD="fixed-point"
+],[
+  enable_float="yes";
+  PC_BUILD="floating-point"
+  PC_LIBM="$LIBM"
+])
+
+AM_CONDITIONAL([FIXED_POINT], [test "$enable_fixed_point" = "yes"])
+
+AC_ARG_ENABLE([fixed-point-debug],
+    [AS_HELP_STRING([--enable-fixed-point-debug], [debug fixed-point implementation])],,
+    [enable_fixed_point_debug=no])
+
+AS_IF([test "$enable_fixed_point_debug" = "yes"],[
+  AC_DEFINE([FIXED_DEBUG], [1], [Debug fixed-point implementation])
+])
+
+AC_ARG_ENABLE([custom-modes],
+    [AS_HELP_STRING([--enable-custom-modes], [enable non-Opus modes, e.g. 44.1 kHz & 2^n frames])],,
+    [enable_custom_modes=no])
+
+AS_IF([test "$enable_custom_modes" = "yes"],[
+  AC_DEFINE([CUSTOM_MODES], [1], [Custom modes])
+  PC_BUILD="$PC_BUILD, custom modes"
+  PC_LIBM="$LIBM"
+])
+
+AM_CONDITIONAL([CUSTOM_MODES], [test "$enable_custom_modes" = "yes"])
 
 has_float_approx=no
 #case "$host_cpu" in
@@ -119,132 +157,116 @@ has_float_approx=no
 #  ;;
 #esac    
 
-ac_enable_fixed="no";
-ac_enable_float="yes";
-AC_ARG_ENABLE(fixed-point, [  --enable-fixed-point       compile without floating point (for machines without a fast enough FPU)],
-[if test "$enableval" = yes; then
-  ac_enable_fixed="yes";
-  ac_enable_float="no";
-  AC_DEFINE([FIXED_POINT], [1], [Compile as fixed-point (for machines without a fast enough FPU)])
-fi])
-
-ac_enable_fixed_debug="no"
-AC_ARG_ENABLE(fixed-point-debug, [  --enable-fixed-point-debug debug fixed-point implementation],
-[if test "$enableval" = yes; then
-  ac_enable_fixed_debug="yes"
-  AC_DEFINE([FIXED_DEBUG], , [Debug fixed-point implementation])
-fi])
-
-ac_enable_custom_modes="no"
-AC_ARG_ENABLE(custom-modes, [  --enable-custom-modes      enable non-Opus modes, e.g. 44.1 kHz & 2^n frames],
-[if test "$enableval" = yes; then
-  ac_enable_custom_modes="yes"
-  AC_DEFINE([CUSTOM_MODES], , [Custom modes])
-fi])
-
-float_approx=$has_float_approx
-AC_ARG_ENABLE(float-approx, [  --enable-float-approx      enable fast approximations for floating point],
-    [ if test "$enableval" = yes; then
-    AC_WARN([Floating point approximations are not supported on all platforms.])
-    float_approx=yes
-    else
-    float_approx=no
-    fi], [ float_approx=$has_float_approx ])
-
-if test "x${float_approx}" = "xyes"; then
-    AC_DEFINE([FLOAT_APPROX], , [Float approximations])
-fi
+AC_ARG_ENABLE([float-approx],
+    [AS_HELP_STRING([--enable-float-approx], [enable fast approximations for floating point])],
+    [if test "$enable_float_approx" = "yes"; then
+       AC_WARN([Floating point approximations are not supported on all platforms.])
+     fi
+    ],
+    [enable_float_approx=$has_float_approx])
+
+AS_IF([test "$enable_float_approx" = "yes"],[
+  AC_DEFINE([FLOAT_APPROX], [1], [Float approximations])
+])
+
+AC_ARG_ENABLE([asm],
+    [AS_HELP_STRING([--disable-asm], [Disable assembly optimizations])],,
+    [enable_asm=yes])
 
 rtcd_support=no
 cpu_arm=no
-AC_ARG_ENABLE(asm,
-    AS_HELP_STRING([--disable-asm], [Disable assembly optimizations]),
-    [ ac_enable_asm=$enableval ], [ ac_enable_asm=yes] )
-if test "x${ac_enable_asm}" = xyes ; then
+
+AS_IF([test "$enable_asm" = "yes"],[
     asm_optimization="no asm for your platform, please send patches"
     case $host_cpu in
     arm*)
         cpu_arm=yes
         AS_GCC_INLINE_ASSEMBLY([asm_optimization="ARM"],
             [asm_optimization="disabled"])
-        if test "x${asm_optimization}" = "xARM" ; then
+        if test "$asm_optimization" = "ARM" ; then
             rtcd_support=yes
             AC_DEFINE([ARMv4_ASM], 1, [Use generic ARMv4 asm optimizations])
             AS_ASM_ARM_EDSP([ARMv5E_ASM=1],[ARMv5E_ASM=0])
-            if test "x${ARMv5E_ASM}" = "x1" ; then
-                AC_DEFINE(ARMv5E_ASM, 1, [Use ARMv5E asm optimizations])
-                asm_optimization="${asm_optimization} (EDSP)"
+            if test "$ARMv5E_ASM" = "1" ; then
+                AC_DEFINE([ARMv5E_ASM], [1], [Use ARMv5E asm optimizations])
+                asm_optimization="$asm_optimization (EDSP)"
             fi
             AS_ASM_ARM_MEDIA([ARMv6_ASM=1],[ARMv6_ASM=0])
-            if test "x${ARMv6_ASM}" = "x1" ; then
-                AC_DEFINE(ARMv6_ASM, 1, [Use ARMv6 asm optimizations])
-                asm_optimization="${asm_optimization} (Media)"
+            if test "$ARMv6_ASM" = "1" ; then
+                AC_DEFINE([ARMv6_ASM], [1], [Use ARMv6 asm optimizations])
+                asm_optimization="$asm_optimization (Media)"
             fi
             AS_ASM_ARM_NEON([ARM_HAVE_NEON=1],[ARM_HAVE_NEON=0])
-            if test "x${ARM_HAVE_NEON}" = "x1" ; then
+            if test "$ARM_HAVE_NEON" = "1" ; then
               AC_DEFINE([ARM_HAVE_NEON], 1, [Use ARM NEON optimizations])
-              asm_optimization="${asm_optimization} (NEON)"
+              asm_optimization="$asm_optimization (NEON)"
             fi
         fi
         ;;
     esac
-else
+],[
     asm_optimization="disabled"
-fi
-
-AC_ARG_ENABLE(rtcd,
-    AS_HELP_STRING([--disable-rtcd], [Disable run-time CPU capabilities detection]),
-    [ ac_enable_rtcd=$enableval ], [ ac_enable_rtcd=yes] )
-if test "x${ac_enable_rtcd}" = xyes -a "x${rtcd_support}" = xyes ; then
-    AC_DEFINE([OPUS_HAVE_RTCD], 1, [Use run-time CPU capabilities detection])
-elif test "x${rtcd_support}" = xno ; then
-    rtcd_support="no rtcd for your platform, please send patches"
-else
+])
+
+AM_CONDITIONAL([CPU_ARM], [test "$cpu_arm" = "yes"])
+
+AC_ARG_ENABLE([rtcd],
+    [AS_HELP_STRING([--disable-rtcd], [Disable run-time CPU capabilities detection])],,
+    [enable_rtcd=yes])
+
+AS_IF([test "$enable_rtcd" = "yes"],[
+    AS_IF([test "$rtcd_support" = "yes"],[
+        AC_DEFINE([OPUS_HAVE_RTCD], [1], [Use run-time CPU capabilities detection])
+    ],[
+        rtcd_support="no rtcd for your platform, please send patches"
+    ])
+],[
     rtcd_support="no"
-fi
-
-ac_enable_assertions="no"
-AC_ARG_ENABLE(assertions, [  --enable-assertions        enable additional software error checking],
-[if test "$enableval" = yes; then
-  ac_enable_assertions="yes"
-  AC_DEFINE([ENABLE_ASSERTIONS], , [Assertions])
-fi])
-
-ac_enable_fuzzing="no"
-AC_ARG_ENABLE(fuzzing, [  --enable-fuzzing           causes the encoder to make random decisions],
-[if test "$enableval" = yes; then
-  ac_enable_fuzzing="yes"
-  AC_DEFINE([FUZZING], , [Fuzzing])
-fi])
-
-ac_enable_doc="yes"
+])
+
+AC_ARG_ENABLE([assertions],
+    [AS_HELP_STRING([--enable-assertions],[enable additional software error checking])],,
+    [enable_assertions=no])
+
+AS_IF([test "$enable_assertions" = "yes"], [
+  AC_DEFINE([ENABLE_ASSERTIONS], [1], [Assertions])
+])
+
+AC_ARG_ENABLE([fuzzing],
+    [AS_HELP_STRING([--enable-fuzzing],[causes the encoder to make random decisions])],,
+    [enable_fuzzing=no])
+
+AS_IF([test "$enable_fuzzing" = "yes"], [
+  AC_DEFINE([FUZZING], [1], [Fuzzing])
+])
+
 AC_ARG_ENABLE([doc],
-  AS_HELP_STRING([--disable-doc], [Do not build API documentation]),
-                 [ac_enable_doc=$enableval])
-AC_CHECK_PROG(HAVE_DOXYGEN, [doxygen], [yes], [no])
-if test "$HAVE_DOXYGEN" != "yes" -o "$ac_enable_doc" != "yes"; then
-  HAVE_DOXYGEN="false"
-  ac_enable_doc="no"
-fi
-AM_CONDITIONAL(HAVE_DOXYGEN, [test $HAVE_DOXYGEN = yes])
-
-ac_enable_extra_programs="yes"
+    [AS_HELP_STRING([--disable-doc], [Do not build API documentation])],,
+    [enable_doc=yes])
+
+AS_IF([test "$enable_doc" = "yes"], [
+  AC_CHECK_PROG(HAVE_DOXYGEN, [doxygen], [yes], [no])
+],[
+  HAVE_DOXYGEN=no
+])
+
+AM_CONDITIONAL([HAVE_DOXYGEN], [test "$HAVE_DOXYGEN" = "yes"])
+
 AC_ARG_ENABLE([extra-programs],
-              AS_HELP_STRING([--disable-extra-programs], [Do not build extra programs (demo and tests)]),
-              [ac_enable_extra_programs=$enableval])
-if test "$ac_enable_extra_programs" != "yes"; then
-  ac_enable_extra_progs="no"
-fi
+    [AS_HELP_STRING([--disable-extra-programs], [Do not build extra programs (demo and tests)])],,
+    [enable_extra_programs=yes])
+
+AM_CONDITIONAL([EXTRA_PROGRAMS], [test "$enable_extra_programs" = "yes"])
+
 
 saved_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -fvisibility=hidden"
 AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
-      [ AC_MSG_RESULT([yes])
-        SYMBOL_VISIBILITY="-fvisibility=hidden" ],
-        AC_MSG_RESULT([no]))
-CFLAGS="$saved_CFLAGS $SYMBOL_VISIBILITY"
-AC_SUBST(SYMBOL_VISIBILITY)
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
+    [ AC_MSG_RESULT([yes]) ],
+    [ AC_MSG_RESULT([no])
+      CFLAGS="$saved_CFLAGS"
+    ])
 
 CFLAGS="$CFLAGS -W"
 
@@ -252,34 +274,20 @@ warn_CFLAGS="-Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-proto
 saved_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS $warn_CFLAGS"
 AC_MSG_CHECKING([if ${CC} supports ${warn_CFLAGS}])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
-      [ AC_MSG_RESULT([yes])
-        EXTRA_WARNS=$warn_CFLAGS ],
-        AC_MSG_RESULT([no]))
-CFLAGS="$saved_CFLAGS $EXTRA_WARNS"
-
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
+    [ AC_MSG_RESULT([yes]) ],
+    [ AC_MSG_RESULT([no])
+      CFLAGS="$saved_CFLAGS"
+    ])
+
+saved_LIBS="$LIBS"
+LIBS="$LIBS $LIBM"
 AC_CHECK_FUNCS([lrintf])
 AC_CHECK_FUNCS([lrint])
-AC_CHECK_FUNCS([__malloc_hook])
+LIBS="$saved_LIBS"
 
-AM_CONDITIONAL([FIXED_POINT], [test x$ac_enable_fixed = xyes])
-AM_CONDITIONAL([CUSTOM_MODES], [test x$ac_enable_custom_modes = xyes])
-AM_CONDITIONAL([EXTRA_PROGRAMS], [test x$ac_enable_extra_programs = xyes])
-AM_CONDITIONAL([CPU_ARM], [test x$cpu_arm = xyes])
+AC_CHECK_FUNCS([__malloc_hook])
 
-dnl subsitutions for the pkg-config files
-if test x$ac_enable_float = xyes; then
-  PC_BUILD="floating-point"
-  PC_LIBM=$LIBM
-else
-  PC_BUILD="fixed-point"
-  PC_LIBM=
-fi
-dnl opus_custom requires libm as well
-if test x$ac_enable_custom_modes = xyes; then
-  PC_BUILD="${PC_BUILD}, custom modes"
-  PC_LIBM=$LIBM
-fi
 AC_SUBST([PC_BUILD])
 AC_SUBST([PC_LIBM])
 
@@ -298,21 +306,21 @@ AC_MSG_NOTICE([
 
       C99 var arrays: ................ ${has_var_arrays}
       C99 lrintf: .................... ${ac_cv_func_lrintf}
-      Alloca: ........................ ${has_alloca}
+      Use alloca: .................... ${use_alloca}
     
     General configuration:
     
-      Floating point support: ........ ${ac_enable_float}
-      Fast float approximations: ..... ${float_approx}
-      Fixed point debugging: ......... ${ac_enable_fixed_debug}
+      Floating point support: ........ ${enable_float}
+      Fast float approximations: ..... ${enable_float_approx}
+      Fixed point debugging: ......... ${enable_fixed_point_debug}
       Assembly optimization: ......... ${asm_optimization}
       Run-time CPU detection: ........ ${rtcd_support}
-      Custom modes: .................. ${ac_enable_custom_modes}
-      Assertion checking: ............ ${ac_enable_assertions}
-      Fuzzing: ....................... ${ac_enable_fuzzing}
+      Custom modes: .................. ${enable_custom_modes}
+      Assertion checking: ............ ${enable_assertions}
+      Fuzzing: ....................... ${enable_fuzzing}
 
-      API documentation: ............. ${ac_enable_doc}
-      Extra programs: ................ ${ac_enable_extra_programs}
+      API documentation: ............. ${enable_doc}
+      Extra programs: ................ ${enable_extra_programs}
 ------------------------------------------------------------------------
 
  Type "make; make install" to compile and install