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([AC_LANG_SOURCE([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="$CFLAGS -Werror"
 196   AC_TRY_LINK([
 197     int foo_alt(void) { return 0; }
 198     typedef int F (void);
 199     F *foo_sel(void) { return foo_alt; }
 200     int foo(void) __attribute__((ifunc("foo_sel")));],
 201     [return foo();], libat_cv_have_ifunc=yes, libat_cv_have_ifunc=no)])
 202   LIBAT_DEFINE_YESNO([HAVE_IFUNC], [$libat_cv_have_ifunc],
 203       [Define to 1 if the target supports __attribute__((ifunc(...))).])
 204 ])
 205
 206 dnl ----------------------------------------------------------------------
 207 dnl This whole bit snagged from libitm.
 208
 209 dnl Check whether the target supports hidden visibility.
 210 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_VISIBILITY], [
 211   AC_CACHE_CHECK([whether the target supports hidden visibility],
 212                  libat_cv_have_attribute_visibility, [
 213   save_CFLAGS="$CFLAGS"
 214   CFLAGS="$CFLAGS -Werror"
 215   AC_TRY_COMPILE([void __attribute__((visibility("hidden"))) foo(void) { }],
 216                  [], libat_cv_have_attribute_visibility=yes,
 217                  libat_cv_have_attribute_visibility=no)
 218   CFLAGS="$save_CFLAGS"])
 219   if test $libat_cv_have_attribute_visibility = yes; then
 220     AC_DEFINE(HAVE_ATTRIBUTE_VISIBILITY, 1,
 221       [Define to 1 if the target supports __attribute__((visibility(...))).])
 222   fi])
 223
 224 dnl Check whether the target supports dllexport
 225 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_DLLEXPORT], [
 226   AC_CACHE_CHECK([whether the target supports dllexport],
 227                  libat_cv_have_attribute_dllexport, [
 228   save_CFLAGS="$CFLAGS"
 229   CFLAGS="$CFLAGS -Werror"
 230   AC_TRY_COMPILE([void __attribute__((dllexport)) foo(void) { }],
 231                  [], libat_cv_have_attribute_dllexport=yes,
 232                  libat_cv_have_attribute_dllexport=no)
 233   CFLAGS="$save_CFLAGS"])
 234   if test $libat_cv_have_attribute_dllexport = yes; then
 235     AC_DEFINE(HAVE_ATTRIBUTE_DLLEXPORT, 1,
 236       [Define to 1 if the target supports __attribute__((dllexport)).])
 237   fi])
 238
 239 dnl Check whether the target supports symbol aliases.
 240 AC_DEFUN([LIBAT_CHECK_ATTRIBUTE_ALIAS], [
 241   AC_CACHE_CHECK([whether the target supports symbol aliases],
 242                  libat_cv_have_attribute_alias, [
 243   AC_TRY_LINK([
 244 void foo(void) { }
 245 extern void bar(void) __attribute__((alias("foo")));],
 246     [bar();], libat_cv_have_attribute_alias=yes, libat_cv_have_attribute_alias=no)])
 247   if test $libat_cv_have_attribute_alias = yes; then
 248     AC_DEFINE(HAVE_ATTRIBUTE_ALIAS, 1,
 249       [Define to 1 if the target supports __attribute__((alias(...))).])
 250   fi])
 251
 252 dnl ----------------------------------------------------------------------
 253 dnl This whole bit snagged from libstdc++-v3.
 254
 255 dnl
 256 dnl LIBAT_ENABLE
 257 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING)
 258 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, permit a|b|c)
 259 dnl    (FEATURE, DEFAULT, HELP-ARG, HELP-STRING, SHELL-CODE-HANDLER)
 260 dnl
 261 dnl See docs/html/17_intro/configury.html#enable for documentation.
 262 dnl
 263 m4_define([LIBAT_ENABLE],[dnl
 264 m4_define([_g_switch],[--enable-$1])dnl
 265 m4_define([_g_help],[AC_HELP_STRING(_g_switch$3,[$4 @<:@default=$2@:>@])])dnl
 266  AC_ARG_ENABLE($1,_g_help,
 267   m4_bmatch([$5],
 268    [^permit ],
 269      [[
 270       case "$enableval" in
 271        m4_bpatsubst([$5],[permit ])) ;;
 272        *) AC_MSG_ERROR(Unknown argument to enable/disable $1) ;;
 273           dnl Idea for future:  generate a URL pointing to
 274           dnl "onlinedocs/configopts.html#whatever"
 275       esac
 276      ]],
 277    [^$],
 278      [[
 279       case "$enableval" in
 280        yes|no) ;;
 281        *) AC_MSG_ERROR(Argument to enable/disable $1 must be yes or no) ;;
 282       esac
 283      ]],
 284    [[$5]]),
 285   [enable_]m4_bpatsubst([$1],-,_)[=][$2])
 286 m4_undefine([_g_switch])dnl
 287 m4_undefine([_g_help])dnl
 288 ])
 289
 290 dnl
 291 dnl If GNU ld is in use, check to see if tricky linker opts can be used.  If
 292 dnl the native linker is in use, all variables will be defined to something
 293 dnl safe (like an empty string).
 294 dnl
 295 dnl Defines:
 296 dnl  SECTION_LDFLAGS='-Wl,--gc-sections' if possible
 297 dnl  OPT_LDFLAGS='-Wl,-O1' if possible
 298 dnl  LD (as a side effect of testing)
 299 dnl Sets:
 300 dnl  with_gnu_ld
 301 dnl  libat_ld_is_gold (possibly)
 302 dnl  libat_gnu_ld_version (possibly)
 303 dnl
 304 dnl The last will be a single integer, e.g., version 1.23.45.0.67.89 will
 305 dnl set libat_gnu_ld_version to 12345.  Zeros cause problems.
 306 dnl
 307 AC_DEFUN([LIBAT_CHECK_LINKER_FEATURES], [
 308   # If we're not using GNU ld, then there's no point in even trying these
 309   # tests.  Check for that first.  We should have already tested for gld
 310   # by now (in libtool), but require it now just to be safe...
 311   test -z "$SECTION_LDFLAGS" && SECTION_LDFLAGS=''
 312   test -z "$OPT_LDFLAGS" && OPT_LDFLAGS=''
 313   AC_REQUIRE([AC_PROG_LD])
 314   AC_REQUIRE([AC_PROG_AWK])
 315
 316   # The name set by libtool depends on the version of libtool.  Shame on us
 317   # for depending on an impl detail, but c'est la vie.  Older versions used
 318   # ac_cv_prog_gnu_ld, but now it's lt_cv_prog_gnu_ld, and is copied back on
 319   # top of with_gnu_ld (which is also set by --with-gnu-ld, so that actually
 320   # makes sense).  We'll test with_gnu_ld everywhere else, so if that isn't
 321   # set (hence we're using an older libtool), then set it.
 322   if test x${with_gnu_ld+set} != xset; then
 323     if test x${ac_cv_prog_gnu_ld+set} != xset; then
 324       # We got through "ac_require(ac_prog_ld)" and still not set?  Huh?
 325       with_gnu_ld=no
 326     else
 327       with_gnu_ld=$ac_cv_prog_gnu_ld
 328     fi
 329   fi
 330
 331   # Start by getting the version number.  I think the libtool test already
 332   # does some of this, but throws away the result.
 333   libat_ld_is_gold=no
 334   if $LD --version 2>/dev/null | grep 'GNU gold'> /dev/null 2>&1; then
 335     libat_ld_is_gold=yes
 336   fi
 337   changequote(,)
 338   ldver=`$LD --version 2>/dev/null |
 339          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'`
 340   changequote([,])
 341   libat_gnu_ld_version=`echo $ldver | \
 342          $AWK -F. '{ if (NF<3) [$]3=0; print ([$]1*100+[$]2)*100+[$]3 }'`
 343
 344   # Set --gc-sections.
 345   if test "$with_gnu_ld" = "notbroken"; then
 346     # GNU ld it is!  Joy and bunny rabbits!
 347
 348     # All these tests are for C++; save the language and the compiler flags.
 349     # Need to do this so that g++ won't try to link in libstdc++
 350     ac_test_CFLAGS="${CFLAGS+set}"
 351     ac_save_CFLAGS="$CFLAGS"
 352     CFLAGS='-x c++  -Wl,--gc-sections'
 353
 354     # Check for -Wl,--gc-sections
 355     # XXX This test is broken at the moment, as symbols required for linking
 356     # are now in libsupc++ (not built yet).  In addition, this test has
 357     # cored on solaris in the past.  In addition, --gc-sections doesn't
 358     # really work at the moment (keeps on discarding used sections, first
 359     # .eh_frame and now some of the glibc sections for iconv).
 360     # Bzzzzt.  Thanks for playing, maybe next time.
 361     AC_MSG_CHECKING([for ld that supports -Wl,--gc-sections])
 362     AC_TRY_RUN([
 363      int main(void)
 364      {
 365        try { throw 1; }
 366        catch (...) { };
 367        return 0;
 368      }
 369     ], [ac_sectionLDflags=yes],[ac_sectionLDflags=no], [ac_sectionLDflags=yes])
 370     if test "$ac_test_CFLAGS" = set; then
 371       CFLAGS="$ac_save_CFLAGS"
 372     else
 373       # this is the suspicious part
 374       CFLAGS=''
 375     fi
 376     if test "$ac_sectionLDflags" = "yes"; then
 377       SECTION_LDFLAGS="-Wl,--gc-sections $SECTION_LDFLAGS"
 378     fi
 379     AC_MSG_RESULT($ac_sectionLDflags)
 380   fi
 381
 382   # Set linker optimization flags.
 383   if test x"$with_gnu_ld" = x"yes"; then
 384     OPT_LDFLAGS="-Wl,-O1 $OPT_LDFLAGS"
 385   fi
 386
 387   AC_SUBST(SECTION_LDFLAGS)
 388   AC_SUBST(OPT_LDFLAGS)
 389 ])
 390
 391
 392 dnl
 393 dnl If GNU ld is in use, check to see if tricky linker opts can be used.  If
 394 dnl the native linker is in use, all variables will be defined to something
 395 dnl safe (like an empty string).
 396 dnl
 397 dnl Defines:
 398 dnl  SECTION_LDFLAGS='-Wl,--gc-sections' if possible
 399 dnl  OPT_LDFLAGS='-Wl,-O1' if possible
 400 dnl  LD (as a side effect of testing)
 401 dnl Sets:
 402 dnl  with_gnu_ld
 403 dnl  libat_ld_is_gold (possibly)
 404 dnl  libat_gnu_ld_version (possibly)
 405 dnl
 406 dnl The last will be a single integer, e.g., version 1.23.45.0.67.89 will
 407 dnl set libat_gnu_ld_version to 12345.  Zeros cause problems.
 408 dnl
 409 AC_DEFUN([LIBAT_CHECK_LINKER_FEATURES], [
 410   # If we're not using GNU ld, then there's no point in even trying these
 411   # tests.  Check for that first.  We should have already tested for gld
 412   # by now (in libtool), but require it now just to be safe...
 413   test -z "$SECTION_LDFLAGS" && SECTION_LDFLAGS=''
 414   test -z "$OPT_LDFLAGS" && OPT_LDFLAGS=''
 415   AC_REQUIRE([AC_PROG_LD])
 416   AC_REQUIRE([AC_PROG_AWK])
 417
 418   # The name set by libtool depends on the version of libtool.  Shame on us
 419   # for depending on an impl detail, but c'est la vie.  Older versions used
 420   # ac_cv_prog_gnu_ld, but now it's lt_cv_prog_gnu_ld, and is copied back on
 421   # top of with_gnu_ld (which is also set by --with-gnu-ld, so that actually
 422   # makes sense).  We'll test with_gnu_ld everywhere else, so if that isn't
 423   # set (hence we're using an older libtool), then set it.
 424   if test x${with_gnu_ld+set} != xset; then
 425     if test x${ac_cv_prog_gnu_ld+set} != xset; then
 426       # We got through "ac_require(ac_prog_ld)" and still not set?  Huh?
 427       with_gnu_ld=no
 428     else
 429       with_gnu_ld=$ac_cv_prog_gnu_ld
 430     fi
 431   fi
 432
 433   # Start by getting the version number.  I think the libtool test already
 434   # does some of this, but throws away the result.
 435   libat_ld_is_gold=no
 436   if $LD --version 2>/dev/null | grep 'GNU gold'> /dev/null 2>&1; then
 437     libat_ld_is_gold=yes
 438   fi
 439   changequote(,)
 440   ldver=`$LD --version 2>/dev/null |
 441          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'`
 442   changequote([,])
 443   libat_gnu_ld_version=`echo $ldver | \
 444          $AWK -F. '{ if (NF<3) [$]3=0; print ([$]1*100+[$]2)*100+[$]3 }'`
 445
 446   # Set --gc-sections.
 447   if test "$with_gnu_ld" = "notbroken"; then
 448     # GNU ld it is!  Joy and bunny rabbits!
 449
 450     # All these tests are for C++; save the language and the compiler flags.
 451     # Need to do this so that g++ won't try to link in libstdc++
 452     ac_test_CFLAGS="${CFLAGS+set}"
 453     ac_save_CFLAGS="$CFLAGS"
 454     CFLAGS='-x c++  -Wl,--gc-sections'
 455
 456     # Check for -Wl,--gc-sections
 457     # XXX This test is broken at the moment, as symbols required for linking
 458     # are now in libsupc++ (not built yet).  In addition, this test has
 459     # cored on solaris in the past.  In addition, --gc-sections doesn't
 460     # really work at the moment (keeps on discarding used sections, first
 461     # .eh_frame and now some of the glibc sections for iconv).
 462     # Bzzzzt.  Thanks for playing, maybe next time.
 463     AC_MSG_CHECKING([for ld that supports -Wl,--gc-sections])
 464     AC_TRY_RUN([
 465      int main(void)
 466      {
 467        try { throw 1; }
 468        catch (...) { };
 469        return 0;
 470      }
 471     ], [ac_sectionLDflags=yes],[ac_sectionLDflags=no], [ac_sectionLDflags=yes])
 472     if test "$ac_test_CFLAGS" = set; then
 473       CFLAGS="$ac_save_CFLAGS"
 474     else
 475       # this is the suspicious part
 476       CFLAGS=''
 477     fi
 478     if test "$ac_sectionLDflags" = "yes"; then
 479       SECTION_LDFLAGS="-Wl,--gc-sections $SECTION_LDFLAGS"
 480     fi
 481     AC_MSG_RESULT($ac_sectionLDflags)
 482   fi
 483
 484   # Set linker optimization flags.
 485   if test x"$with_gnu_ld" = x"yes"; then
 486     OPT_LDFLAGS="-Wl,-O1 $OPT_LDFLAGS"
 487   fi
 488
 489   AC_SUBST(SECTION_LDFLAGS)
 490   AC_SUBST(OPT_LDFLAGS)
 491 ])
 492
 493
 494 dnl
 495 dnl Add version tags to symbols in shared library (or not), additionally
 496 dnl marking other symbols as private/local (or not).
 497 dnl
 498 dnl --enable-symvers=style adds a version script to the linker call when
 499 dnl       creating the shared library.  The choice of version script is
 500 dnl       controlled by 'style'.
 501 dnl --disable-symvers does not.
 502 dnl  +  Usage:  LIBAT_ENABLE_SYMVERS[(DEFAULT)]
 503 dnl       Where DEFAULT is either 'yes' or 'no'.  Passing `yes' tries to
 504 dnl       choose a default style based on linker characteristics.  Passing
 505 dnl       'no' disables versioning.
 506 dnl
 507 AC_DEFUN([LIBAT_ENABLE_SYMVERS], [
 508
 509 LIBAT_ENABLE(symvers,yes,[=STYLE],
 510   [enables symbol versioning of the shared library],
 511   [permit yes|no|gnu*|sun])
 512
 513 # If we never went through the LIBAT_CHECK_LINKER_FEATURES macro, then we
 514 # don't know enough about $LD to do tricks...
 515 AC_REQUIRE([LIBAT_CHECK_LINKER_FEATURES])
 516
 517 # Turn a 'yes' into a suitable default.
 518 if test x$enable_symvers = xyes ; then
 519   # FIXME  The following test is too strict, in theory.
 520   if test $enable_shared = no || test "x$LD" = x; then
 521     enable_symvers=no
 522   else
 523     if test $with_gnu_ld = yes ; then
 524       enable_symvers=gnu
 525     else
 526       case ${target_os} in
 527         # Sun symbol versioning exists since Solaris 2.5.
 528         solaris2.[[5-9]]* | solaris2.1[[0-9]]*)
 529           enable_symvers=sun ;;
 530         *)
 531           enable_symvers=no ;;
 532       esac
 533     fi
 534   fi
 535 fi
 536
 537 # Check if 'sun' was requested on non-Solaris 2 platforms.
 538 if test x$enable_symvers = xsun ; then
 539   case ${target_os} in
 540     solaris2*)
 541       # All fine.
 542       ;;
 543     *)
 544       # Unlikely to work.
 545       AC_MSG_WARN([=== You have requested Sun symbol versioning, but])
 546       AC_MSG_WARN([=== you are not targetting Solaris 2.])
 547       AC_MSG_WARN([=== Symbol versioning will be disabled.])
 548       enable_symvers=no
 549       ;;
 550   esac
 551 fi
 552
 553 # Check to see if libgcc_s exists, indicating that shared libgcc is possible.
 554 if test $enable_symvers != no; then
 555   AC_MSG_CHECKING([for shared libgcc])
 556   ac_save_CFLAGS="$CFLAGS"
 557   CFLAGS=' -lgcc_s'
 558   AC_TRY_LINK(, [return 0;], libat_shared_libgcc=yes, libat_shared_libgcc=no)
 559   CFLAGS="$ac_save_CFLAGS"
 560   if test $libat_shared_libgcc = no; then
 561     cat > conftest.c <<EOF
 562 int main (void) { return 0; }
 563 EOF
 564 changequote(,)dnl
 565     libat_libgcc_s_suffix=`${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
 566                              -shared -shared-libgcc -o conftest.so \
 567                              conftest.c -v 2>&1 >/dev/null \
 568                              | sed -n 's/^.* -lgcc_s\([^ ]*\) .*$/\1/p'`
 569 changequote([,])dnl
 570     rm -f conftest.c conftest.so
 571     if test x${libat_libgcc_s_suffix+set} = xset; then
 572       CFLAGS=" -lgcc_s$libat_libgcc_s_suffix"
 573       AC_TRY_LINK(, [return 0;], libat_shared_libgcc=yes)
 574       CFLAGS="$ac_save_CFLAGS"
 575     fi
 576   fi
 577   AC_MSG_RESULT($libat_shared_libgcc)
 578 fi
 579
 580 # For GNU ld, we need at least this version.  The format is described in
 581 # LIBAT_CHECK_LINKER_FEATURES above.
 582 libat_min_gnu_ld_version=21400
 583 # XXXXXXXXXXX libat_gnu_ld_version=21390
 584
 585 # Check to see if unspecified "yes" value can win, given results above.
 586 # Change "yes" into either "no" or a style name.
 587 if test $enable_symvers != no && test $libat_shared_libgcc = yes; then
 588   if test $with_gnu_ld = yes; then
 589     if test $libat_gnu_ld_version -ge $libat_min_gnu_ld_version ; then
 590       enable_symvers=gnu
 591     elif test $libat_ld_is_gold = yes ; then
 592       enable_symvers=gnu
 593     else
 594       # The right tools, the right setup, but too old.  Fallbacks?
 595       AC_MSG_WARN(=== Linker version $libat_gnu_ld_version is too old for)
 596       AC_MSG_WARN(=== full symbol versioning support in this release of GCC.)
 597       AC_MSG_WARN(=== You would need to upgrade your binutils to version)
 598       AC_MSG_WARN(=== $libat_min_gnu_ld_version or later and rebuild GCC.)
 599       if test $libat_gnu_ld_version -ge 21200 ; then
 600         # Globbing fix is present, proper block support is not.
 601         dnl AC_MSG_WARN([=== Dude, you are soooo close.  Maybe we can fake it.])
 602         dnl enable_symvers=???
 603         AC_MSG_WARN([=== Symbol versioning will be disabled.])
 604         enable_symvers=no
 605       else
 606         # 2.11 or older.
 607         AC_MSG_WARN([=== Symbol versioning will be disabled.])
 608         enable_symvers=no
 609       fi
 610     fi
 611   elif test $enable_symvers = sun; then
 612     : All interesting versions of Sun ld support sun style symbol versioning.
 613   else
 614     # just fail for now
 615     AC_MSG_WARN([=== You have requested some kind of symbol versioning, but])
 616     AC_MSG_WARN([=== either you are not using a supported linker, or you are])
 617     AC_MSG_WARN([=== not building a shared libgcc_s (which is required).])
 618     AC_MSG_WARN([=== Symbol versioning will be disabled.])
 619     enable_symvers=no
 620   fi
 621 fi
 622 if test $enable_symvers = gnu; then
 623   AC_DEFINE(LIBAT_GNU_SYMBOL_VERSIONING, 1,
 624             [Define to 1 if GNU symbol versioning is used for libatomic.])
 625 fi
 626
 627 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB, test $enable_symvers != no)
 628 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB_GNU, test $enable_symvers = gnu)
 629 AM_CONDITIONAL(LIBAT_BUILD_VERSIONED_SHLIB_SUN, test $enable_symvers = sun)
 630 AC_MSG_NOTICE(versioning on shared library symbols is $enable_symvers)
 631 ])
 632
 633 dnl ----------------------------------------------------------------------
 634 sinclude(../libtool.m4)
 635 sinclude(../config/enable.m4)
 636 sinclude(../config/cet.m4)
 637 dnl The lines below arrange for aclocal not to bring an installed
 638 dnl libtool.m4 into aclocal.m4, while still arranging for automake to
 639 dnl add a definition of LIBTOOL to Makefile.in.
 640 ifelse(,,,[AC_SUBST(LIBTOOL)
 641 AC_DEFUN([AM_PROG_LIBTOOL])
 642 AC_DEFUN([AC_LIBTOOL_DLOPEN])
 643 AC_DEFUN([AC_PROG_LD])
 644 ])