libatomic/acinclude.m4

   1 dnl
   2 dnl Unconditionally define a preprocessor macro, translating the shell
   3 dnl macro from yes/no to 1/0.
   4 dnl
   5 AC_DEFUN([LIBAT_DEFINE_YESNO], [
   6   yesno=`echo $2 | tr 'yesno' '1  0 '`
   7   AC_DEFINE_UNQUOTED([$1], $yesno, [$3])
   8 ])
   9 dnl
  10 dnl Iterate over all of the modes we're prepared to check.
  11 dnl
  12 AC_DEFUN([LIBAT_FORALL_MODES],
  13   [$1(QI,1)
  14   $1(HI,2)
  15   $1(SI,4)
  16   $1(DI,8)
  17   $1(TI,16)]
  18 )
  19 dnl
  20 dnl Check for builtin types by mode.
  21 dnl
  22 dnl A less interesting of size checking than autoconf normally provides.
  23 dnl We know that gcc always provides <stdint.h>, but we don't often
  24 dnl provide a builtin type for TImode.
  25 dnl
  26 AC_DEFUN([LIBAT_HAVE_INT_MODE],[
  27   AC_CACHE_CHECK([for $2 byte integer],[libat_cv_have_mode_$1],
  28     [AC_COMPILE_IFELSE([int x __attribute__((mode($1)));],
  29       [libat_cv_have_mode_$1=yes],[libat_cv_have_mode_$1=no])])
  30   LIBAT_DEFINE_YESNO([HAVE_INT$2], [$libat_cv_have_mode_$1],
  31       [Have support for $2 byte integers.])
  32   if test x$libat_cv_have_mode_$1 = xyes; then
  33     SIZES="$SIZES $2"
  34   fi
  35 ])
  36 dnl
  37 dnl Check for atomic builtins.
  38 dnl See:
  39 dnl http://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
  40 dnl
  41 dnl This checks to see if the host supports the compiler-generated
  42 dnl builtins for atomic operations for various integral sizes.
  43 dnl
  44 AC_DEFUN([LIBAT_TEST_ATOMIC_INIT],[
  45   # Do link tests if possible, instead asm tests, limited to some platforms
  46   # see discussion in PR target/40134, PR libstdc++/40133 and the thread
  47   # starting at http://gcc.gnu.org/ml/gcc-patches/2009-07/msg00322.html
  48   atomic_builtins_link_tests=no
  49   if test x$gcc_no_link != xyes; then
  50     # Can do link tests. Limit to some tested platforms
  51     case "$host" in
  52       *-*-linux* | *-*-uclinux* | *-*-kfreebsd*-gnu | *-*-gnu*)
  53         atomic_builtins_link_tests=yes
  54         ;;
  55     esac
  56   fi
  57 ])
  58 AC_DEFUN([LIBAT_TEST_ATOMIC_BUILTIN],[
  59   AC_CACHE_CHECK([$1],[$2],[
  60     AC_LANG_CONFTEST([AC_LANG_PROGRAM([],[$3])])
  61     if test x$atomic_builtins_link_tests = xyes; then
  62       if AC_TRY_EVAL(ac_link); then
  63         eval $2=yes
  64       else
  65         eval $2=no
  66       fi
  67     else
  68       old_CFLAGS="$CFLAGS"
  69       # Compile unoptimized.
  70       CFLAGS="$CFLAGS -O0 -S"
  71       if AC_TRY_EVAL(ac_compile); then
  72         if grep __atomic_ conftest.s >/dev/null 2>&1 ; then
  73           eval $2=no
  74         else
  75           eval $2=yes
  76         fi
  77       else
  78         eval $2=no
  79       fi
  80       CFLAGS="$old_CFLAGS"
  81     fi
  82     rm -f conftest*
  83   ])
  84 ])
  85
  86 dnl
  87 dnl Test if we have __atomic_load and __atomic_store for mode $1, size $2
  88 dnl
  89 AC_DEFUN([LIBAT_HAVE_ATOMIC_LOADSTORE],[
  90   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_load/store for size $2],
  91     [libat_cv_have_at_ldst_$2],
  92     [typedef int T __attribute__((mode($1)));
  93      T *x; volatile T sink; asm("" : "=g"(x));
  94      sink = __atomic_load_n(x, 0);
  95      __atomic_store_n(x, sink, 0);])
  96   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_LDST_$2], [$libat_cv_have_at_ldst_$2],
  97         [Have __atomic_load/store for $2 byte integers.])
  98   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_LDST_$2 HAVE_ATOMIC_LDST_$2])
  99   AH_BOTTOM([#define FAST_ATOMIC_LDST_$2 HAVE_ATOMIC_LDST_$2])
 100 ])
 101
 102 dnl
 103 dnl Test if we have __atomic_test_and_set for mode $1, size $2
 104 dnl
 105 AC_DEFUN([LIBAT_HAVE_ATOMIC_TAS],[
 106   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_test_and_set for size $2],
 107     [libat_cv_have_at_tas_$2],
 108     [typedef int T __attribute__((mode($1))); T *x; asm("" : "=g"(x));
 109      __atomic_test_and_set(x, 0);])
 110   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_TAS_$2], [$libat_cv_have_at_tas_$2],
 111         [Have __atomic_test_and_set for $2 byte integers.])
 112   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_TAS_$2 HAVE_ATOMIC_TAS_$2])
 113 ])
 114
 115 dnl
 116 dnl Test if we have __atomic_exchange for mode $1, size $2
 117 dnl
 118 AC_DEFUN([LIBAT_HAVE_ATOMIC_EXCHANGE],[
 119   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_exchange for size $2],
 120     [libat_cv_have_at_exch_$2],
 121     [typedef int T __attribute__((mode($1))); T *x; asm("" : "=g"(x));
 122      __atomic_exchange_n(x, 0, 0);])
 123   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_EXCHANGE_$2], [$libat_cv_have_at_exch_$2],
 124         [Have __atomic_exchange for $2 byte integers.])
 125   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_EXCHANGE_$2 HAVE_ATOMIC_EXCHANGE_$2])
 126 ])
 127
 128 dnl
 129 dnl Test if we have __atomic_compare_exchange for mode $1, size $2
 130 dnl
 131 AC_DEFUN([LIBAT_HAVE_ATOMIC_CAS],[
 132   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_compare_exchange for size $2],
 133     [libat_cv_have_at_cas_$2],
 134     [typedef int T __attribute__((mode($1))); T *x, *y;
 135      asm("" : "=g"(x), "=g"(y));
 136      __atomic_compare_exchange_n(x, y, 0, 0, 0, 0);])
 137   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_CAS_$2], [$libat_cv_have_at_cas_$2],
 138         [Have __atomic_compare_exchange for $2 byte integers.])
 139   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_CAS_$2 HAVE_ATOMIC_CAS_$2])
 140 ])
 141
 142 dnl
 143 dnl Test if we have __atomic_fetch_add for mode $1, size $2
 144 dnl
 145 AC_DEFUN([LIBAT_HAVE_ATOMIC_FETCH_ADD],[
 146   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_fetch_add for size $2],
 147     [libat_cv_have_at_fadd_$2],
 148     [typedef int T __attribute__((mode($1))); T *x, y;
 149      asm("" : "=g"(x), "=g"(y));
 150      __atomic_fetch_add (x, y, 0);
 151      __atomic_add_fetch (x, y, 0);])
 152   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_FETCH_ADD_$2], [$libat_cv_have_at_fadd_$2],
 153         [Have __atomic_fetch_add for $2 byte integers.])
 154   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_FETCH_ADD_$2 HAVE_ATOMIC_FETCH_ADD_$2])
 155 ])
 156
 157 dnl
 158 dnl Test if we have __atomic_fetch_op for all op for mode $1, size $2
 159 dnl
 160 AC_DEFUN([LIBAT_HAVE_ATOMIC_FETCH_OP],[
 161   LIBAT_TEST_ATOMIC_BUILTIN([for __atomic_fetch_op for size $2],
 162     [libat_cv_have_at_fop_$2],
 163     [typedef int T __attribute__((mode($1))); T *x, y;
 164      asm("" : "=g"(x), "=g"(y));
 165      __atomic_fetch_add (x, y, 0); __atomic_add_fetch (x, y, 0);
 166      __atomic_fetch_sub (x, y, 0); __atomic_sub_fetch (x, y, 0);
 167      __atomic_fetch_and (x, y, 0); __atomic_and_fetch (x, y, 0);
 168      __atomic_fetch_nand (x, y, 0); __atomic_nand_fetch (x, y, 0);
 169      __atomic_fetch_xor (x, y, 0); __atomic_xor_fetch (x, y, 0);
 170      __atomic_fetch_or (x, y, 0);  __atomic_or_fetch (x, y, 0); ])
 171   LIBAT_DEFINE_YESNO([HAVE_ATOMIC_FETCH_OP_$2], [$libat_cv_have_at_fop_$2],
 172         [Have __atomic_fetch_op for all op for $2 byte integers.])
 173   AH_BOTTOM([#define MAYBE_HAVE_ATOMIC_FETCH_OP_$2 HAVE_ATOMIC_FETCH_OP_$2])
 174 ])
 175
 176 dnl
 177 dnl Test for the size of the target word.
 178 dnl
 179 AC_DEFUN([LIBAT_WORDSIZE],[
 180   AC_CACHE_CHECK([for the word size],[libat_cv_wordsize],
 181     [AC_COMPUTE_INT(libat_cv_wordsize,
 182       [sizeof(word)], [typedef int word __attribute__((mode(word)));],
 183       AC_ERROR([Could not determine word size.]))])
 184   AC_DEFINE_UNQUOTED(WORDSIZE, $libat_cv_wordsize,
 185     [The word size in bytes of the machine.])
 186 ])
 187
 188 dnl
 189 dnl Check whether the target supports the ifunc attribute.
 190 dnl
 191 AC_DEFUN([LIBAT_CHECK_IFUNC], [
 192   AC_CACHE_CHECK([whether the target supports the ifunc attribute],
 193                  libat_cv_have_ifunc, [
 194   save_CFLAGS="$CFLAGS"
 195   CFLAGS="$CFLAGS -Werror"
 196   AC_TRY_LINK([
 197     int foo_alt(void) { return 0; }
 198     void *foo_sel(void) { return foo_alt; }
 199     int foo(void) __attribute__((ifunc("foo_sel")));],
 200     [return foo();], libat_cv_have_ifunc=yes, libat_cv_have_ifunc=no)])
 201   LIBAT_DEFINE_YESNO([HAVE_IFUNC], [$libat_cv_have_ifunc],
 202       [Define to 1 if the target supports __attribute__((ifunc(...))).])
 203 ])
 204
 205 dnl ----------------------------------------------------------------------
 206 dnl This whole bit snagged from libitm.
 207
 208 dnl Check whether the target supports hidden visibility.
 209 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_VISIBILITY], [
 210   AC_CACHE_CHECK([whether the target supports hidden visibility],
 211                  libat_cv_have_attribute_visibility, [
 212   save_CFLAGS="$CFLAGS"
 213   CFLAGS="$CFLAGS -Werror"
 214   AC_TRY_COMPILE([void __attribute__((visibility("hidden"))) foo(void) { }],
 215                  [], libat_cv_have_attribute_visibility=yes,
 216                  libat_cv_have_attribute_visibility=no)
 217   CFLAGS="$save_CFLAGS"])
 218   if test $libat_cv_have_attribute_visibility = yes; then
 219     AC_DEFINE(HAVE_ATTRIBUTE_VISIBILITY, 1,
 220       [Define to 1 if the target supports __attribute__((visibility(...))).])
 221   fi])
 222
 223 dnl Check whether the target supports dllexport
 224 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_DLLEXPORT], [
 225   AC_CACHE_CHECK([whether the target supports dllexport],
 226                  libat_cv_have_attribute_dllexport, [
 227   save_CFLAGS="$CFLAGS"
 228   CFLAGS="$CFLAGS -Werror"
 229   AC_TRY_COMPILE([void __attribute__((dllexport)) foo(void) { }],
 230                  [], libat_cv_have_attribute_dllexport=yes,
 231                  libat_cv_have_attribute_dllexport=no)
 232   CFLAGS="$save_CFLAGS"])
 233   if test $libat_cv_have_attribute_dllexport = yes; then
 234     AC_DEFINE(HAVE_ATTRIBUTE_DLLEXPORT, 1,
 235       [Define to 1 if the target supports __attribute__((dllexport)).])
 236   fi])
 237
 238 dnl Check whether the target supports symbol aliases.
 239 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_ALIAS], [
 240   AC_CACHE_CHECK([whether the target supports symbol aliases],
 241                  libat_cv_have_attribute_alias, [
 242   AC_TRY_LINK([
 243 void foo(void) { }
 244 extern void bar(void) __attribute__((alias("foo")));],
 245     [bar();], libat_cv_have_attribute_alias=yes, libat_cv_have_attribute_alias=no)])
 246   if test $libat_cv_have_attribute_alias = yes; then
 247     AC_DEFINE(HAVE_ATTRIBUTE_ALIAS, 1,
 248       [Define to 1 if the target supports __attribute__((alias(...))).])
 249   fi])
 250
 251 dnl ----------------------------------------------------------------------
 252 dnl This whole bit snagged from libstdc++-v3.
 253
 254 dnl
 255 dnl LIBAT_ENABLE
 256 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING)
 257 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, permit a|b|c)
 258 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, SHELL-CODE-HANDLER)
 259 dnl
 260 dnl See docs/html/17_intro/configury.html#enable for documentation.
 261 dnl
 262 m4_define([LIBAT_ENABLE],[dnl
 263 m4_define([_g_switch],[--enable-$1])dnl
 264 m4_define([_g_help],[AC_HELP_STRING(_g_switch$3,[$4 @<:@default=$2@:>@])])dnl
 265  AC_ARG_ENABLE($1,_g_help,
 266   m4_bmatch([$5],
 267    [^permit ],
 268      [[
 269       case "$enableval" in
 270        m4_bpatsubst([$5],[permit ])) ;;
 271        *) AC_MSG_ERROR(Unknown argument to enable/disable $1) ;;
 272           dnl Idea for future:  generate a URL pointing to
 273           dnl "onlinedocs/configopts.html#whatever"
 274       esac
 275      ]],
 276    [^$],
 277      [[
 278       case "$enableval" in
 279        yes|no) ;;
 280        *) AC_MSG_ERROR(Argument to enable/disable $1 must be yes or no) ;;
 281       esac
 282      ]],
 283    [[$5]]),
 284   [enable_]m4_bpatsubst([$1],-,_)[=][$2])
 285 m4_undefine([_g_switch])dnl
 286 m4_undefine([_g_help])dnl
 287 ])
 288
 289 dnl
 290 dnl If GNU ld is in use, check to see if tricky linker opts can be used.  If
 291 dnl the native linker is in use, all variables will be defined to something
 292 dnl safe (like an empty string).
 293 dnl
 294 dnl Defines:
 295 dnl  SECTION_LDFLAGS='-Wl,--gc-sections' if possible
 296 dnl  OPT_LDFLAGS='-Wl,-O1' if possible
 297 dnl  LD (as a side effect of testing)
 298 dnl Sets:
 299 dnl  with_gnu_ld
 300 dnl  libat_ld_is_gold (possibly)
 301 dnl  libat_gnu_ld_version (possibly)
 302 dnl
 303 dnl The last will be a single integer, e.g., version 1.23.45.0.67.89 will
 304 dnl set libat_gnu_ld_version to 12345.  Zeros cause problems.
 305 dnl
 306 AC_DEFUN([LIBAT_CHECK_LINKER_FEATURES], [
 307   # If we're not using GNU ld, then there's no point in even trying these
 308   # tests.  Check for that first.  We should have already tested for gld
 309   # by now (in libtool), but require it now just to be safe...
 310   test -z "$SECTION_LDFLAGS" && SECTION_LDFLAGS=''
 311   test -z "$OPT_LDFLAGS" && OPT_LDFLAGS=''
 312   AC_REQUIRE([AC_PROG_LD])
 313   AC_REQUIRE([AC_PROG_AWK])
 314
 315   # The name set by libtool depends on the version of libtool.  Shame on us
 316   # for depending on an impl detail, but c'est la vie.  Older versions used
 317   # ac_cv_prog_gnu_ld, but now it's lt_cv_prog_gnu_ld, and is copied back on
 318   # top of with_gnu_ld (which is also set by --with-gnu-ld, so that actually
 319   # makes sense).  We'll test with_gnu_ld everywhere else, so if that isn't
 320   # set (hence we're using an older libtool), then set it.
 321   if test x${with_gnu_ld+set} != xset; then
 322     if test x${ac_cv_prog_gnu_ld+set} != xset; then
 323       # We got through "ac_require(ac_prog_ld)" and still not set?  Huh?
 324       with_gnu_ld=no
 325     else
 326       with_gnu_ld=$ac_cv_prog_gnu_ld
 327     fi
 328   fi
 329
 330   # Start by getting the version number.  I think the libtool test already
 331   # does some of this, but throws away the result.
 332   libat_ld_is_gold=no
 333   if $LD --version 2>/dev/null | grep 'GNU gold'> /dev/null 2>&1; then
 334     libat_ld_is_gold=yes
 335   fi
 336   changequote(,)
 337   ldver=`$LD --version 2>/dev/null |
 338          sed -e 's/GNU gold /GNU ld /;s/GNU ld version /GNU ld /;s/GNU ld ([^)]*) /GNU ld /;s/GNU ld \([0-9.][0-9.]*\).*/\1/; q'`
 339   changequote([,])
 340   libat_gnu_ld_version=`echo $ldver | \
 341          $AWK -F. '{ if (NF<3) [$]3=0; print ([$]1*100+[$]2)*100+[$]3 }'`
 342
 343   # Set --gc-sections.
 344   if test "$with_gnu_ld" = "notbroken"; then
 345     # GNU ld it is!  Joy and bunny rabbits!
 346
 347     # All these tests are for C++; save the language and the compiler flags.
 348     # Need to do this so that g++ won't try to link in libstdc++
 349     ac_test_CFLAGS="${CFLAGS+set}"
 350     ac_save_CFLAGS="$CFLAGS"
 351     CFLAGS='-x c++  -Wl,--gc-sections'
 352
 353     # Check for -Wl,--gc-sections
 354     # XXX This test is broken at the moment, as symbols required for linking
 355     # are now in libsupc++ (not built yet).  In addition, this test has
 356     # cored on solaris in the past.  In addition, --gc-sections doesn't
 357     # really work at the moment (keeps on discarding used sections, first
 358     # .eh_frame and now some of the glibc sections for iconv).
 359     # Bzzzzt.  Thanks for playing, maybe next time.
 360     AC_MSG_CHECKING([for ld that supports -Wl,--gc-sections])
 361     AC_TRY_RUN([
 362      int main(void)
 363      {
 364        try { throw 1; }
 365        catch (...) { };
 366        return 0;
 367      }
 368     ], [ac_sectionLDflags=yes],[ac_sectionLDflags=no], [ac_sectionLDflags=yes])
 369     if test "$ac_test_CFLAGS" = set; then
 370       CFLAGS="$ac_save_CFLAGS"
 371     else
 372       # this is the suspicious part
 373       CFLAGS=''
 374     fi
 375     if test "$ac_sectionLDflags" = "yes"; then
 376       SECTION_LDFLAGS="-Wl,--gc-sections $SECTION_LDFLAGS"
 377     fi
 378     AC_MSG_RESULT($ac_sectionLDflags)
 379   fi
 380
 381   # Set linker optimization flags.
 382   if test x"$with_gnu_ld" = x"yes"; then
 383     OPT_LDFLAGS="-Wl,-O1 $OPT_LDFLAGS"
 384   fi
 385
 386   AC_SUBST(SECTION_LDFLAGS)
 387   AC_SUBST(OPT_LDFLAGS)
 388 ])
 389
 390
 391 dnl
 392 dnl If GNU ld is in use, check to see if tricky linker opts can be used.  If
 393 dnl the native linker is in use, all variables will be defined to something
 394 dnl safe (like an empty string).
 395 dnl
 396 dnl Defines:
 397 dnl  SECTION_LDFLAGS='-Wl,--gc-sections' if possible
 398 dnl  OPT_LDFLAGS='-Wl,-O1' if possible
 399 dnl  LD (as a side effect of testing)
 400 dnl Sets:
 401 dnl  with_gnu_ld
 402 dnl  libat_ld_is_gold (possibly)
 403 dnl  libat_gnu_ld_version (possibly)
 404 dnl
 405 dnl The last will be a single integer, e.g., version 1.23.45.0.67.89 will
 406 dnl set libat_gnu_ld_version to 12345.  Zeros cause problems.
 407 dnl
 408 AC_DEFUN([LIBAT_CHECK_LINKER_FEATURES], [
 409   # If we're not using GNU ld, then there's no point in even trying these
 410   # tests.  Check for that first.  We should have already tested for gld
 411   # by now (in libtool), but require it now just to be safe...
 412   test -z "$SECTION_LDFLAGS" && SECTION_LDFLAGS=''
 413   test -z "$OPT_LDFLAGS" && OPT_LDFLAGS=''
 414   AC_REQUIRE([AC_PROG_LD])
 415   AC_REQUIRE([AC_PROG_AWK])
 416
 417   # The name set by libtool depends on the version of libtool.  Shame on us
 418   # for depending on an impl detail, but c'est la vie.  Older versions used
 419   # ac_cv_prog_gnu_ld, but now it's lt_cv_prog_gnu_ld, and is copied back on
 420   # top of with_gnu_ld (which is also set by --with-gnu-ld, so that actually
 421   # makes sense).  We'll test with_gnu_ld everywhere else, so if that isn't
 422   # set (hence we're using an older libtool), then set it.
 423   if test x${with_gnu_ld+set} != xset; then
 424     if test x${ac_cv_prog_gnu_ld+set} != xset; then
 425       # We got through "ac_require(ac_prog_ld)" and still not set?  Huh?
 426       with_gnu_ld=no
 427     else
 428       with_gnu_ld=$ac_cv_prog_gnu_ld
 429     fi
 430   fi
 431
 432   # Start by getting the version number.  I think the libtool test already
 433   # does some of this, but throws away the result.
 434   libat_ld_is_gold=no
 435   if $LD --version 2>/dev/null | grep 'GNU gold'> /dev/null 2>&1; then
 436     libat_ld_is_gold=yes
 437   fi
 438   changequote(,)
 439   ldver=`$LD --version 2>/dev/null |
 440          sed -e 's/GNU gold /GNU ld /;s/GNU ld version /GNU ld /;s/GNU ld ([^)]*) /GNU ld /;s/GNU ld \([0-9.][0-9.]*\).*/\1/; q'`
 441   changequote([,])
 442   libat_gnu_ld_version=`echo $ldver | \
 443          $AWK -F. '{ if (NF<3) [$]3=0; print ([$]1*100+[$]2)*100+[$]3 }'`
 444
 445   # Set --gc-sections.
 446   if test "$with_gnu_ld" = "notbroken"; then
 447     # GNU ld it is!  Joy and bunny rabbits!
 448
 449     # All these tests are for C++; save the language and the compiler flags.
 450     # Need to do this so that g++ won't try to link in libstdc++
 451     ac_test_CFLAGS="${CFLAGS+set}"
 452     ac_save_CFLAGS="$CFLAGS"
 453     CFLAGS='-x c++  -Wl,--gc-sections'
 454
 455     # Check for -Wl,--gc-sections
 456     # XXX This test is broken at the moment, as symbols required for linking
 457     # are now in libsupc++ (not built yet).  In addition, this test has
 458     # cored on solaris in the past.  In addition, --gc-sections doesn't
 459     # really work at the moment (keeps on discarding used sections, first
 460     # .eh_frame and now some of the glibc sections for iconv).
 461     # Bzzzzt.  Thanks for playing, maybe next time.
 462     AC_MSG_CHECKING([for ld that supports -Wl,--gc-sections])
 463     AC_TRY_RUN([
 464      int main(void)
 465      {
 466        try { throw 1; }
 467        catch (...) { };
 468        return 0;
 469      }
 470     ], [ac_sectionLDflags=yes],[ac_sectionLDflags=no], [ac_sectionLDflags=yes])
 471     if test "$ac_test_CFLAGS" = set; then
 472       CFLAGS="$ac_save_CFLAGS"
 473     else
 474       # this is the suspicious part
 475       CFLAGS=''
 476     fi
 477     if test "$ac_sectionLDflags" = "yes"; then
 478       SECTION_LDFLAGS="-Wl,--gc-sections $SECTION_LDFLAGS"
 479     fi
 480     AC_MSG_RESULT($ac_sectionLDflags)
 481   fi
 482
 483   # Set linker optimization flags.
 484   if test x"$with_gnu_ld" = x"yes"; then
 485     OPT_LDFLAGS="-Wl,-O1 $OPT_LDFLAGS"
 486   fi
 487
 488   AC_SUBST(SECTION_LDFLAGS)
 489   AC_SUBST(OPT_LDFLAGS)
 490 ])
 491
 492
 493 dnl
 494 dnl Add version tags to symbols in shared library (or not), additionally
 495 dnl marking other symbols as private/local (or not).
 496 dnl
 497 dnl --enable-symvers=style adds a version script to the linker call when
 498 dnl       creating the shared library.  The choice of version script is
 499 dnl       controlled by 'style'.
 500 dnl --disable-symvers does not.
 501 dnl  +  Usage:  LIBAT_ENABLE_SYMVERS[(DEFAULT)]
 502 dnl       Where DEFAULT is either 'yes' or 'no'.  Passing `yes' tries to
 503 dnl       choose a default style based on linker characteristics.  Passing
 504 dnl       'no' disables versioning.
 505 dnl
 506 AC_DEFUN([LIBAT_ENABLE_SYMVERS], [
 507
 508 LIBAT_ENABLE(symvers,yes,[=STYLE],
 509   [enables symbol versioning of the shared library],
 510   [permit yes|no|gnu*|sun])
 511
 512 # If we never went through the LIBAT_CHECK_LINKER_FEATURES macro, then we
 513 # don't know enough about $LD to do tricks...
 514 AC_REQUIRE([LIBAT_CHECK_LINKER_FEATURES])
 515
 516 # Turn a 'yes' into a suitable default.
 517 if test x$enable_symvers = xyes ; then
 518   # FIXME  The following test is too strict, in theory.
 519   if test $enable_shared = no || test "x$LD" = x; then
 520     enable_symvers=no
 521   else
 522     if test $with_gnu_ld = yes ; then
 523       enable_symvers=gnu
 524     else
 525       case ${target_os} in
 526         # Sun symbol versioning exists since Solaris 2.5.
 527         solaris2.[[5-9]]* | solaris2.1[[0-9]]*)
 528           enable_symvers=sun ;;
 529         *)
 530           enable_symvers=no ;;
 531       esac
 532     fi
 533   fi
 534 fi
 535
 536 # Check if 'sun' was requested on non-Solaris 2 platforms.
 537 if test x$enable_symvers = xsun ; then
 538   case ${target_os} in
 539     solaris2*)
 540       # All fine.
 541       ;;
 542     *)
 543       # Unlikely to work.
 544       AC_MSG_WARN([=== You have requested Sun symbol versioning, but])
 545       AC_MSG_WARN([=== you are not targetting Solaris 2.])
 546       AC_MSG_WARN([=== Symbol versioning will be disabled.])
 547       enable_symvers=no
 548       ;;
 549   esac
 550 fi
 551
 552 # Check to see if libgcc_s exists, indicating that shared libgcc is possible.
 553 if test $enable_symvers != no; then
 554   AC_MSG_CHECKING([for shared libgcc])
 555   ac_save_CFLAGS="$CFLAGS"
 556   CFLAGS=' -lgcc_s'
 557   AC_TRY_LINK(, [return 0;], libat_shared_libgcc=yes, libat_shared_libgcc=no)
 558   CFLAGS="$ac_save_CFLAGS"
 559   if test $libat_shared_libgcc = no; then
 560     cat > conftest.c <<EOF
 561 int main (void) { return 0; }
 562 EOF
 563 changequote(,)dnl
 564     libat_libgcc_s_suffix=`${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
 565                              -shared -shared-libgcc -o conftest.so \
 566                              conftest.c -v 2>&1 >/dev/null \
 567                              | sed -n 's/^.* -lgcc_s\([^ ]*\) .*$/\1/p'`
 568 changequote([,])dnl
 569     rm -f conftest.c conftest.so
 570     if test x${libat_libgcc_s_suffix+set} = xset; then
 571       CFLAGS=" -lgcc_s$libat_libgcc_s_suffix"
 572       AC_TRY_LINK(, [return 0;], libat_shared_libgcc=yes)
 573       CFLAGS="$ac_save_CFLAGS"
 574     fi
 575   fi
 576   AC_MSG_RESULT($libat_shared_libgcc)
 577 fi
 578
 579 # For GNU ld, we need at least this version.  The format is described in
 580 # LIBAT_CHECK_LINKER_FEATURES above.
 581 libat_min_gnu_ld_version=21400
 582 # XXXXXXXXXXX libat_gnu_ld_version=21390
 583
 584 # Check to see if unspecified "yes" value can win, given results above.
 585 # Change "yes" into either "no" or a style name.
 586 if test $enable_symvers != no && test $libat_shared_libgcc = yes; then
 587   if test $with_gnu_ld = yes; then
 588     if test $libat_gnu_ld_version -ge $libat_min_gnu_ld_version ; then
 589       enable_symvers=gnu
 590     elif test $libat_ld_is_gold = yes ; then
 591       enable_symvers=gnu
 592     else
 593       # The right tools, the right setup, but too old.  Fallbacks?
 594       AC_MSG_WARN(=== Linker version $libat_gnu_ld_version is too old for)
 595       AC_MSG_WARN(=== full symbol versioning support in this release of GCC.)
 596       AC_MSG_WARN(=== You would need to upgrade your binutils to version)
 597       AC_MSG_WARN(=== $libat_min_gnu_ld_version or later and rebuild GCC.)
 598       if test $libat_gnu_ld_version -ge 21200 ; then
 599         # Globbing fix is present, proper block support is not.
 600         dnl AC_MSG_WARN([=== Dude, you are soooo close.  Maybe we can fake it.])
 601         dnl enable_symvers=???
 602         AC_MSG_WARN([=== Symbol versioning will be disabled.])
 603         enable_symvers=no
 604       else
 605         # 2.11 or older.
 606         AC_MSG_WARN([=== Symbol versioning will be disabled.])
 607         enable_symvers=no
 608       fi
 609     fi
 610   elif test $enable_symvers = sun; then
 611     : All interesting versions of Sun ld support sun style symbol versioning.
 612   else
 613     # just fail for now
 614     AC_MSG_WARN([=== You have requested some kind of symbol versioning, but])
 615     AC_MSG_WARN([=== either you are not using a supported linker, or you are])
 616     AC_MSG_WARN([=== not building a shared libgcc_s (which is required).])
 617     AC_MSG_WARN([=== Symbol versioning will be disabled.])
 618     enable_symvers=no
 619   fi
 620 fi
 621 if test $enable_symvers = gnu; then
 622   AC_DEFINE(LIBAT_GNU_SYMBOL_VERSIONING, 1,
 623             [Define to 1 if GNU symbol versioning is used for libatomic.])
 624 fi
 625
 626 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB, test $enable_symvers != no)
 627 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB_GNU, test $enable_symvers = gnu)
 628 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB_SUN, test $enable_symvers = sun)
 629 AC_MSG_NOTICE(versioning on shared library symbols is $enable_symvers)
 630 ])
 631
 632 dnl ----------------------------------------------------------------------
 633 sinclude(../libtool.m4)
 634 dnl The lines below arrange for aclocal not to bring an installed
 635 dnl libtool.m4 into aclocal.m4, while still arranging for automake to
 636 dnl add a definition of LIBTOOL to Makefile.in.
 637 ifelse(,,,[AC_SUBST(LIBTOOL)
 638 AC_DEFUN([AM_PROG_LIBTOOL])
 639 AC_DEFUN([AC_LIBTOOL_DLOPEN])
 640 AC_DEFUN([AC_PROG_LD])
 641 ])