binutils-gdb/gold/configure.ac

dnl Process this file with autoconf to produce a configure script.
dnl
dnl   Copyright (C) 2006-2019 Free Software Foundation, Inc.
dnl
dnl This file is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU General Public License as published by
dnl the Free Software Foundation; either version 3 of the License, or
dnl (at your option) any later version.
dnl
dnl This program is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
dnl GNU General Public License for more details.
dnl
dnl You should have received a copy of the GNU General Public License
dnl along with this program; see the file COPYING3.  If not see
dnl <http://www.gnu.org/licenses/>.
dnl

AC_INIT(gold, 0.1)
AC_CONFIG_SRCDIR(gold.cc)

AC_CANONICAL_TARGET

AM_INIT_AUTOMAKE([no-dist parallel-tests])

AM_CONFIG_HEADER(config.h:config.in)

AC_USE_SYSTEM_EXTENSIONS

# PR 14072
AH_VERBATIM([00_CONFIG_H_CHECK],
[/* Check that config.h is #included before system headers
   (this works only for glibc, but that should be enough).  */
#if defined(__GLIBC__) && !defined(__FreeBSD_kernel__) && !defined(__CONFIG_H__)
#  error config.h must be #included before system headers
#endif
#define __CONFIG_H__ 1])

AC_ARG_WITH(sysroot,
[  --with-sysroot[=DIR]    search for usr/lib et al within DIR],
[sysroot=$withval], [sysroot=no])

if test "$sysroot" = "yes"; then
  sysroot='${exec_prefix}/${target_alias}/sys-root'
elif test "$sysroot" = "no"; then
  sysroot=
fi

sysroot_relocatable=0
if test -n "$sysroot"; then
  case "$sysroot" in
    "${prefix}" | "${prefix}/"* | \
    "${exec_prefix}" | "${exec_prefix}/"* | \
    '${prefix}' | '${prefix}/'*| \
    '${exec_prefix}' | '${exec_prefix}/'*)
      sysroot_relocatable=1
      ;;
  esac
fi

AC_DEFINE_UNQUOTED(TARGET_SYSTEM_ROOT, "$sysroot",
  [System root for target files])
AC_DEFINE_UNQUOTED(TARGET_SYSTEM_ROOT_RELOCATABLE, $sysroot_relocatable,
  [Whether the system root can be relocated])

dnl "install_as_default" is true if the linker to be installed as the
dnl default linker, ld.
dnl "installed_linker" is the installed gold linker name.

installed_linker=ld.gold
AC_ARG_ENABLE(gold,
[[  --enable-gold[=ARG]     build gold [ARG={default,yes,no}]]],
[case "${enableval}" in
 default)
   install_as_default=yes
   ;;
 yes)
   if test x${enable_ld} = xno; then
     install_as_default=yes
   fi
   ;;
 esac],
[install_as_default=no])
AC_SUBST(install_as_default)
AC_SUBST(installed_linker)

AC_PLUGINS
if test "$plugins" = "yes"; then
  AC_DEFINE(ENABLE_PLUGINS, 1,
	    [Define to enable linker plugins])
fi
AM_CONDITIONAL(PLUGINS, test "$plugins" = "yes")

# Decide if -z relro should be enabled in ELF linker by default.
ac_default_ld_z_relro=unset
# Provide a configure time option to override our default.
AC_ARG_ENABLE(relro,
	      AS_HELP_STRING([--enable-relro],
	      [enable -z relro in ELF linker by default]),
[case "${enableval}" in
  yes)  ac_default_ld_z_relro=1 ;;
  no)  ac_default_ld_z_relro=0 ;;
esac])dnl
if test "${ac_default_ld_z_relro}" = unset; then
  ac_default_ld_z_relro=1
fi
AC_DEFINE_UNQUOTED(DEFAULT_LD_Z_RELRO,
  $ac_default_ld_z_relro,
  [Define to 1 if you want to enable -z relro in ELF linker by default.])

AC_ARG_ENABLE([targets],
[  --enable-targets        alternative target configurations],
[case "${enableval}" in
  yes | "")
    AC_MSG_ERROR([--enable-targets option must specify target names or 'all'])
    ;;
  no)
    enable_targets=
    ;;
  *)
    enable_targets=$enableval
    ;;
esac],
[# For now, enable all targets by default
 enable_targets=all
])

# Canonicalize the enabled targets.
if test -n "$enable_targets"; then
  for targ in `echo $enable_targets | sed -e 's/,/ /g'`; do
    result=`$ac_config_sub $targ 2>/dev/null`
    if test -n "$result"; then
      canon_targets="$canon_targets $result"
    else
      # Permit unrecognized target names, like "all".
      canon_targets="$canon_targets $targ"
    fi
  done
fi

# Decide which "--hash-style" to use by default
# Provide a configure time option to override our default.
AC_ARG_ENABLE([default-hash-style],
AS_HELP_STRING([--enable-default-hash-style={sysv,gnu,both}],
	       [use this default hash style]),
[case "${enable_default_hash_style}" in
  sysv | gnu | both) ;;
  *) AC_MSG_ERROR([bad value ${enable_default_hash_style} for enable-default-hash-style option]) ;;
esac],
[case "${target}" in
  # Enable gnu hash only on GNU targets, but not mips
  mips*-*-*) enable_default_hash_style=sysv ;;
  *-*-gnu* | *-*-linux* | *-*-nacl*) enable_default_hash_style=both ;;
  *) enable_default_hash_style=sysv ;;
esac])

AC_DEFINE_UNQUOTED([DEFAULT_HASH_STYLE],
  ["${enable_default_hash_style}"],
  [Set the default --hash-style value])

# See which specific instantiations we need.
targetobjs=
all_targets=
default_machine=
default_size=
default_big_endian=
default_osabi=ELFOSABI_NONE
targ_32_little=
targ_32_big=
targ_64_little=
targ_64_big=
for targ in $target $canon_targets; do
  if test "$targ" = "all"; then
    targ_32_little=yes
    targ_32_big=yes
    targ_64_little=yes
    targ_64_big=yes
    all_targets=yes
  else
    . ${srcdir}/configure.tgt

    if test "$targ_obj" = "UNKNOWN"; then
      AC_MSG_ERROR("unsupported target $targ")
    else
      targetobjs="$targetobjs ${targ_obj}.\$(OBJEXT)"
      if test "$targ_extra_obj" != ""; then
        targetobjs="$targetobjs ${targ_extra_obj}.\$(OBJEXT)"
      fi
      if test "$targ_size" = "32" -o "$targ_extra_size" = "32"; then
	  if test "$targ_big_endian" = "true" \
	      -o "$targ_extra_big_endian" = "true"; then
	      targ_32_big=yes
	  fi
	  if test "$targ_big_endian" = "false" \
	      -o "$targ_extra_big_endian" = "false"; then
	      targ_32_little=yes
	  fi
      fi
      if test "$targ_size" = "64" -o "$targ_extra_size" = "64"; then
	  if test "$targ_big_endian" = "true" \
	      -o "$targ_extra_big_endian" = "true"; then
	      targ_64_big=yes
	  fi
	  if test "$targ_big_endian" = "false" \
	      -o "$targ_extra_big_endian" = "false"; then
	      targ_64_little=yes
	  fi
      fi

      if test "$target" = "$targ"; then
        default_machine=$targ_machine
	default_size=$targ_size
	default_big_endian=$targ_big_endian
	default_osabi=$targ_osabi

	AM_CONDITIONAL(DEFAULT_TARGET_AARCH64, test "$targ_obj" = "aarch64")
	AM_CONDITIONAL(DEFAULT_TARGET_ARM, test "$targ_obj" = "arm")
	AM_CONDITIONAL(DEFAULT_TARGET_I386, test "$targ_obj" = "i386")
	AM_CONDITIONAL(DEFAULT_TARGET_POWERPC, test "$targ_obj" = "powerpc")
	AM_CONDITIONAL(DEFAULT_TARGET_SPARC, test "$targ_obj" = "sparc")
	AM_CONDITIONAL(DEFAULT_TARGET_S390, test "$targ_obj" = "s390")
	target_x86_64=no
	target_x32=no
	if test "$targ_obj" = "x86_64"; then
	  case "$target" in
	  x86_64*-linux-gnux32)
	    target_x32=yes
	    default_size=32
	    ;;
	  *)
	    target_x86_64=yes
	    ;;
	  esac
	fi
	AM_CONDITIONAL(DEFAULT_TARGET_X86_64, test "$target_x86_64" = "yes")
	AM_CONDITIONAL(DEFAULT_TARGET_X32, test "$target_x32" = "yes")
	AM_CONDITIONAL(DEFAULT_TARGET_X86_64_OR_X32,
		       test "$target_x86_64" = "yes" -o "$target_x32" = "yes")
	AM_CONDITIONAL(DEFAULT_TARGET_TILEGX, test "$targ_obj" = "tilegx")
        AM_CONDITIONAL(DEFAULT_TARGET_MIPS, test "$targ_obj" = "mips")
	DEFAULT_TARGET=${targ_obj}
	AC_SUBST(DEFAULT_TARGET)
      fi
    fi
  fi
done

# Remove any duplicates.
to=""
for t in $targetobjs; do
  case " $to " in
  *" $t "*) ;;
  *) to="$to $t" ;;
  esac
done
targetobjs=$to

if test -n "$targ_32_little"; then
  AC_DEFINE(HAVE_TARGET_32_LITTLE, 1,
	      [Define to support 32-bit little-endian targets])
fi
if test -n "$targ_32_big"; then
  AC_DEFINE(HAVE_TARGET_32_BIG, 1,
	      [Define to support 32-bit big-endian targets])
fi
if test -n "$targ_64_little"; then
  AC_DEFINE(HAVE_TARGET_64_LITTLE, 1,
	      [Define to support 64-bit little-endian targets])
fi
if test -n "$targ_64_big"; then
  AC_DEFINE(HAVE_TARGET_64_BIG, 1,
	      [Define to support 64-bit big-endian targets])
fi

if test -n "$all_targets"; then
  TARGETOBJS='$(ALL_TARGETOBJS)'
else
  TARGETOBJS="$targetobjs"
fi
AC_SUBST(TARGETOBJS)

AC_DEFINE_UNQUOTED(GOLD_DEFAULT_MACHINE, $default_machine,
		   [Default machine code])
AC_DEFINE_UNQUOTED(GOLD_DEFAULT_SIZE, $default_size,
		   [Default size (32 or 64)])
AC_DEFINE_UNQUOTED(GOLD_DEFAULT_BIG_ENDIAN, $default_big_endian,
		   [Default big endian (true or false)])
AC_DEFINE_UNQUOTED(GOLD_DEFAULT_OSABI, $default_osabi,
		   [Default OSABI code])

AC_ARG_WITH(lib-path,
[  --with-lib-path=dir1:dir2...  set default LIB_PATH],
[case "$withval" in
 yes) LIB_PATH='"/lib:/usr/lib"' ;;
 no) LIB_PATH='""' ;;
 *) LIB_PATH='"'"$withval"'"' ;;
 esac],
[LIB_PATH='"::DEFAULT::"'])
AC_DEFINE_UNQUOTED(LIB_PATH, $LIB_PATH,
		   [Default library search path])
if test "x$target_alias" = "x" -o "x$host_alias" = "x$target_alias"; then
  AC_DEFINE(NATIVE_LINKER, 1, [Whether configured as a native linker])
fi

AC_CHECK_TOOL(NM, nm)

AC_PROG_CC
AC_PROG_CXX
AC_PROG_YACC
AC_PROG_RANLIB
AC_PROG_INSTALL
AC_PROG_LN_S

AC_GNU_SOURCE

ZW_GNU_GETTEXT_SISTER_DIR
AM_PO_SUBDIRS

AC_C_BIGENDIAN

AC_EXEEXT

AM_CONDITIONAL(NATIVE_LINKER,
  test "x$target_alias" = "x" -o "x$host_alias" = "x$target_alias")
AM_CONDITIONAL(GCC, test "$GCC" = yes)

AM_CONDITIONAL(NATIVE_OR_CROSS_LINKER,
  test "x$target_alias" = "x" -o "x$host_alias" = "x$target_alias" -o "x$host_alias" = "x$build_alias")

dnl Test for whether static linking is supported.  Some systems do not
dnl install static libraries.  This only affects the set of tests that
dnl we run.
AC_CACHE_CHECK([whether static linking works], [gold_cv_lib_static],
[LDFLAGS_hold=$LDFLAGS
LDFLAGS="$LDFLAGS -static"
AC_LINK_IFELSE([
AC_LANG_PROGRAM([[void f() { }]])],
[gold_cv_lib_static=yes], [gold_cv_lib_static=no])
LDFLAGS=$LDFLAGS_hold])
AM_CONDITIONAL(HAVE_STATIC, test "$gold_cv_lib_static" = "yes")

dnl Some architectures do not support taking pointers of functions
dnl defined in shared libraries except in -fPIC mode.  We need to
dnl tell the unittest framework if we're compiling for one of those
dnl targets, so it doesn't try to run the tests that do that.
AM_CONDITIONAL(FN_PTRS_IN_SO_WITHOUT_PIC, [
  case $target_cpu in
    powerpc*) false;;
    x86_64) false;;
    sparc64) false;;
    s390x) false;;
    *) true;;
  esac])

dnl Test for gcc 4.1 or later.  Full support for -mcmodel=medium is
dnl only available in gcc 4.1.
AC_CACHE_CHECK([for gcc >= 4.1], [gold_cv_prog_gcc41],
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#if !defined __GNUC__
error
#elif __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1)
error
#endif
])], [gold_cv_prog_gcc41=yes], [gold_cv_prog_gcc41=no])])

save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -mcmodel=medium"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([int i;])], [have_mcmodel_medium=yes], [have_mcmodel_medium=no])
CFLAGS="$save_CFLAGS"
dnl Whether we can test -mcmodel=medium.
AM_CONDITIONAL(MCMODEL_MEDIUM,
[test "$target_cpu" = "x86_64" -a "$have_mcmodel_medium" = "yes" -a "$gold_cv_prog_gcc41" = "yes"])

AC_CACHE_CHECK([whether $CC supports -fmerge-constants],
	       [gold_cv_merge_constants], [
save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -fmerge-constants"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([const char *s = "foo";])],
		  [gold_cv_merge_constants=yes],
		  [gold_cv_merge_constants=no])
CFLAGS="$save_CFLAGS"])
AC_SUBST([MERGE_CONSTANTS_FLAG])
AS_IF([test "$gold_cv_merge_constants" = yes],
      [MERGE_CONSTANTS_FLAG=-fmerge-constants],
      [MERGE_CONSTANTS_FLAG=])

dnl Test for __thread support.
AC_CACHE_CHECK([for thread support], [gold_cv_c_thread],
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([__thread int i = 1;])],
[gold_cv_c_thread=yes], [gold_cv_c_thread=no])])

AM_CONDITIONAL(TLS, test "$gold_cv_c_thread" = "yes")

dnl On GNU/Linux TLS in static programs only works when using glibc
dnl 2.4 or later.
AC_CACHE_CHECK([for glibc >= 2.4], [gold_cv_lib_glibc24],
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <features.h>
#if !defined __GLIBC__
error
#elif __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 4)
error
#endif
])], [gold_cv_lib_glibc24=yes], [gold_cv_lib_glibc24=no])])

AM_CONDITIONAL(STATIC_TLS, test "$gold_cv_lib_glibc24" = "yes")

dnl Test for #pragma omp threadprivate
AC_CACHE_CHECK([for omp support], [gold_cv_c_threadprivate],
[save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -fopenmp"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <omp.h>
int i;
#pragma omp threadprivate (i)
])], [gold_cv_c_threadprivate=yes], [gold_cv_c_threadprivate=no])
CFLAGS="$save_CFLAGS"])
if test "$gold_cv_c_threadprivate" = "yes"; then
  AC_DEFINE(HAVE_OMP_SUPPORT, 1,
	    [Define if compiler supports #pragma omp threadprivate])
fi
AM_CONDITIONAL(OMP_SUPPORT, test "$gold_cv_c_threadprivate" = "yes")

dnl Test for the -ftls-dialect=gnu2 option.
dnl Use -Werror in case of compilers that make unknown -m options warnings.
dnl They would pass the test here, but fail in actual use when $WARN_CFLAGS
dnl gets set later by default Autoconf magic to include -Werror.  (We are
dnl assuming here that there is no compiler that groks -mtls-dialect=gnu2
dnl but does not grok -Werror.)
save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Werror -fpic -mtls-dialect=gnu2"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
__thread int i;
void foo (void)
{
  i = 10;
}
])], [have_tls_gnu2=yes], [have_tls_gnu2=no])
CFLAGS="$save_CFLAGS"
AM_CONDITIONAL(TLS_GNU2_DIALECT, test "$have_tls_gnu2" = "yes")

dnl On GNU/Linux TLS descriptors are supported by the dynamic loader
dnl only with glibc 2.9 or later.
AC_CACHE_CHECK([for glibc >= 2.9], [gold_cv_lib_glibc29],
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <features.h>
#if !defined __GLIBC__
error
#elif __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 9)
error
#endif
])], [gold_cv_lib_glibc29=yes], [gold_cv_lib_glibc29=no])])

AM_CONDITIONAL(TLS_DESCRIPTORS, test "$gold_cv_lib_glibc29" = "yes")

dnl Test for the -frandom-seed option.
AC_CACHE_CHECK([for -frandom-seed support], [gold_cv_c_random_seed],
[save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -frandom-seed=foo"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([int i;])], [gold_cv_c_random_seed=yes],
[gold_cv_c_random_seed=no])
CFLAGS="$save_CFLAGS"])
if test "$gold_cv_c_random_seed" = "yes"; then
  # In Makefile, '$@' will be expanded to be the name of the file
  # being built, providing a unique seed for each file.
  RANDOM_SEED_CFLAGS=-frandom-seed=\$@
fi
AC_SUBST(RANDOM_SEED_CFLAGS)

dnl On GNU/Linux ifunc is supported by the dynamic linker in glibc
dnl 2.11 or later, and by binutils 2.20.1 or later.
AC_CACHE_CHECK([for glibc ifunc support], [gold_cv_lib_glibc_ifunc],
[save_LDFLAGS="$LDFLAGS"
LDFLAGS="$LDFLAGS -static"
AC_LINK_IFELSE([AC_LANG_PROGRAM([[
#include <features.h>
#if !defined __GLIBC__
error
#elif __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 11)
error
#endif
void func (void) { }
void invoke (void);
__asm__(".type invoke, %gnu_indirect_function");
typedef void (*funcptr) (void);
funcptr dispatch (void) __asm__ ("invoke");
funcptr dispatch (void) { return &func; }]],
[[invoke();]])
], [
if ${NM} conftest$EXEEXT | grep "__rela\?_iplt_start" >/dev/null 2>&1; then
  gold_cv_lib_glibc_ifunc=both
else
  gold_cv_lib_glibc_ifunc=dyn
fi], [gold_cv_lib_glibc_ifunc=no])
LDFLAGS="$save_LDFLAGS"])

AM_CONDITIONAL(IFUNC, test "$gold_cv_lib_glibc_ifunc" != "no")
AM_CONDITIONAL(IFUNC_STATIC, test "$gold_cv_lib_glibc_ifunc" = "both")

AM_BINUTILS_WARNINGS

WARN_CXXFLAGS=`echo ${WARN_CFLAGS} | sed -e 's/-Wstrict-prototypes//' -e 's/-Wmissing-prototypes//' -e 's/-Wshadow//'`
AC_SUBST(WARN_CXXFLAGS)

AC_ARG_WITH(gold-ldflags,
[  --with-gold-ldflags=FLAGS  additional link flags for gold],
[if test "$withval" = "no" -o "$withval" = "yes"; then
   GOLD_LDFLAGS=
 else
   GOLD_LDFLAGS=$withval
 fi],
[GOLD_LDFLAGS=])
AC_SUBST(GOLD_LDFLAGS)

AC_ARG_WITH(gold-ldadd,
[  --with-gold-ldadd=LIBS     additional libraries for gold],
[if test "$withval" = "no" -o "$withval" = "yes"; then
   GOLD_LDADD=
 else
   GOLD_LDADD=$withval
 fi],
[GOLD_LDADD=])
AC_SUBST(GOLD_LDADD)

dnl Force support for large files by default.  This may need to be
dnl host dependent.  If build == host, we can check getconf LFS_CFLAGS.
LFS_CFLAGS="-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64"
AC_SUBST(LFS_CFLAGS)

AC_CHECK_HEADERS(sys/mman.h)
AC_CHECK_FUNCS(chsize mmap link)
AC_REPLACE_FUNCS(pread ftruncate ffsll)

AC_CACHE_CHECK([mremap with MREMAP_MAYMOVE], [gold_cv_lib_mremap_maymove],
[AC_LINK_IFELSE([
AC_LANG_PROGRAM([[
#include <sys/mman.h>
void f() { mremap (0, 0, 0, MREMAP_MAYMOVE); }
]])], [gold_cv_lib_mremap_maymove=yes], [gold_cv_lib_mremap_maymove=no])])
if test "$gold_cv_lib_mremap_maymove" = "yes"; then
  AC_DEFINE(HAVE_MREMAP, 1,
    [Define to 1 if you have the mremap function with MREMAP_MAYMOVE support])
else
  AC_LIBOBJ(mremap)
fi

# Link in zlib if we can.  This allows us to write compressed sections.
AM_ZLIB

AC_ARG_ENABLE([threads],
[[  --enable-threads[=ARG]  multi-threaded linking [ARG={auto,yes,no}]]],
[case "${enableval}" in
  yes | "") threads=yes ;;
  no) threads=no ;;
  auto) threads=auto ;;
  *) threads=yes ;;
 esac],
[threads=auto])

if test "$threads" = "yes"; then
  AX_PTHREAD([threads=yes], AC_MSG_ERROR([pthread not found]))
elif test "$threads" = "auto"; then
  AX_PTHREAD([threads=yes], [threads=no])
fi

if test "$threads" = "yes"; then
  AC_DEFINE(ENABLE_THREADS, 1,
	    [Define to do multi-threaded linking])
fi
AM_CONDITIONAL(THREADS, test "$threads" = "yes")

dnl We have to check these in C, not C++, because autoconf generates
dnl tests which have no type information, and current glibc provides
dnl multiple declarations of functions like basename when compiling
dnl with C++.
AC_CHECK_DECLS([basename, ffs, asprintf, vasprintf, snprintf, vsnprintf, strverscmp])

dnl Check if gcc supports the -gpubnames option.
dnl Use -Werror in case of compilers that make unknown -g options warnings.
dnl They would pass the test here, but fail in actual use when $WARN_CFLAGS
dnl gets set later by default Autoconf magic to include -Werror.  (We are
dnl assuming here that there is no compiler that groks -gpubnames
dnl but does not grok -Werror.)
save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Werror -gpubnames"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([int i;])], [have_pubnames=yes], [have_pubnames=no])
CFLAGS="$save_CFLAGS"
AM_CONDITIONAL(HAVE_PUBNAMES, test "$have_pubnames" = "yes")

dnl Check if gcc supports the -fno-use-linker-plugin option.
save_CFLAGS="$CFLAGS"
CFLAGS="$CFLAGS -Werror -fno-use-linker-plugin"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([int i;])], [have_no_use_linker_plugin=yes], [have_no_use_linker_plugin=no])
CFLAGS="$save_CFLAGS"
AM_CONDITIONAL(HAVE_NO_USE_LINKER_PLUGIN, test "$have_no_use_linker_plugin" = "yes")

AC_LANG_PUSH(C++)

AC_CHECK_HEADERS(unordered_set unordered_map)
AC_CHECK_HEADERS(tr1/unordered_set tr1/unordered_map)
AC_CHECK_HEADERS(ext/hash_map ext/hash_set)
AC_CHECK_HEADERS(byteswap.h)

dnl When plugins enabled dynamic loader interface is required. Check headers
dnl which may provide this interface. Add the necessary library to link.
AC_CHECK_HEADERS(windows.h)
AC_CHECK_HEADERS(dlfcn.h)
AC_SEARCH_LIBS(dlopen, [dl dld])
case "$ac_cv_search_dlopen" in
  no*) DLOPEN_LIBS="";;
  *)   DLOPEN_LIBS="$ac_cv_search_dlopen";;
esac
AC_SUBST(DLOPEN_LIBS)

AC_CHECK_FUNCS(mallinfo posix_fallocate fallocate readv sysconf times mkdtemp)
AC_CHECK_DECLS([basename, ffs, asprintf, vasprintf, snprintf, vsnprintf, strverscmp, strndup, memmem])

# Use of ::std::tr1::unordered_map::rehash causes undefined symbols
# at link time with some versions of GCC.
AC_CACHE_CHECK([whether ::std::tr1::unordered_map::rehash is usable.],
[gold_cv_unordered_map_rehash],
[AC_LINK_IFELSE([AC_LANG_PROGRAM([[
#include <tr1/unordered_map>
void bar() { ::std::tr1::unordered_map<int, int> x; x.rehash(10); }
]])], [gold_cv_unordered_map_rehash=yes], [gold_cv_unordered_map_rehash=no])])
if test "$gold_cv_unordered_map_rehash" = "yes"; then
  AC_DEFINE(HAVE_TR1_UNORDERED_MAP_REHASH, 1,
	    [Define if ::std::tr1::unordered_map::rehash is usable])
fi

# Use of tr1/unordered_map with off_t as a key is not supported on GCC
# 4.1.xx when compiling in 32-bit mode with a 64-bit off_t type.
AC_CACHE_CHECK([whether std::tr1::hash<off_t> is defined],
[gold_cv_hash_off_t],
[CXXFLAGS_hold=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $LFS_CFLAGS"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
#include <sys/types.h>
#include <tr1/unordered_map>
std::tr1::hash<off_t> h;
])],
[gold_cv_hash_off_t=yes],
[gold_cv_hash_off_t=no])
CXXFLAGS=$CXXFLAGS_hold])
if test "$gold_cv_hash_off_t" = "yes"; then
   AC_DEFINE(HAVE_TR1_HASH_OFF_T, 1,
	     [Define if std::tr1::hash<off_t> is usable])
fi

# gcc 4.3.0 doesn't recognize the printf attribute on a template
# function.  Check for that.  This is gcc bug 35546.  This test can
# probably be removed after the bug has been fixed for a while.
AC_CACHE_CHECK([whether we can use attributes with template functions],
[gold_cv_template_attribute],
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([
template<typename T> extern void foo(const char*, ...)
  __attribute__ ((__format__ (__printf__, 1, 2)));
template<typename T> void foo(const char* format, ...) {}
void bar() { foo<int>("%s\n", "foo"); }
])], [gold_cv_template_attribute=yes], [gold_cv_template_attribute=no])])
if test "$gold_cv_template_attribute" = "yes"; then
  AC_DEFINE(HAVE_TEMPLATE_ATTRIBUTES, 1,
	    [Define if attributes work on C++ templates])
fi

dnl Check if the system has struct stat::st_mtim.
AC_CACHE_CHECK([for struct stat::st_mtim.],
[gold_cv_stat_st_mtim],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <sys/stat.h>
long bar() { struct stat s; return (long)(s.st_mtim.tv_sec + s.st_mtim.tv_sec);}
]])], [gold_cv_stat_st_mtim=yes], [gold_cv_stat_st_mtim=no])])
if test "$gold_cv_stat_st_mtim" = "yes"; then
  AC_DEFINE(HAVE_STAT_ST_MTIM, 1,
	    [Define if struct stat has a field st_mtim with timespec for mtime])
fi

AC_LANG_POP(C++)

AC_CHECK_HEADERS(locale.h)
AC_CHECK_FUNCS(setlocale)
AM_LC_MESSAGES

AM_MAINTAINER_MODE

AC_OUTPUT(Makefile testsuite/Makefile po/Makefile.in:po/Make-in)