config/tls.m4

   1 dnl Check whether the target supports TLS.
   2 AC_DEFUN([GCC_CHECK_TLS], [
   3   AC_REQUIRE([AC_CANONICAL_HOST])
   4   GCC_ENABLE(tls, yes, [], [Use thread-local storage])
   5   AC_CACHE_CHECK([whether the target supports thread-local storage],
   6                  gcc_cv_have_tls, [
   7     AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
   8       [dnl If the test case passed with dynamic linking, try again with
   9        dnl static linking, but only if static linking is supported (not
  10        dnl on Solaris 10).  This fails with some older Red Hat releases.
  11       chktls_save_LDFLAGS="$LDFLAGS"
  12       LDFLAGS="-static $LDFLAGS"
  13       AC_LINK_IFELSE([int main() { return 0; }],
  14         AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
  15                       [gcc_cv_have_tls=yes], [gcc_cv_have_tls=no],[]),
  16         [gcc_cv_have_tls=yes])
  17       LDFLAGS="$chktls_save_LDFLAGS"
  18       if test $gcc_cv_have_tls = yes; then
  19         dnl So far, the binutils and the compiler support TLS.
  20         dnl Also check whether the libc supports TLS, i.e. whether a variable
  21         dnl with __thread linkage has a different address in different threads.
  22         dnl First, find the thread_CFLAGS necessary for linking a program that
  23         dnl calls pthread_create.
  24         chktls_save_CFLAGS="$CFLAGS"
  25         thread_CFLAGS=failed
  26         for flag in '' '-pthread' '-lpthread'; do
  27           CFLAGS="$flag $chktls_save_CFLAGS"
  28           AC_LINK_IFELSE(
  29             [AC_LANG_PROGRAM(
  30                [#include <pthread.h>
  31                 void *g(void *d) { return NULL; }],
  32                [pthread_t t; pthread_create(&t,NULL,g,NULL);])],
  33             [thread_CFLAGS="$flag"])
  34           if test "X$thread_CFLAGS" != Xfailed; then
  35             break
  36           fi
  37         done
  38         CFLAGS="$chktls_save_CFLAGS"
  39         if test "X$thread_CFLAGS" != Xfailed; then
  40           CFLAGS="$thread_CFLAGS $chktls_save_CFLAGS"
  41           AC_RUN_IFELSE(
  42             [AC_LANG_PROGRAM(
  43                [#include <pthread.h>
  44                 __thread int a;
  45                 static int *a_in_other_thread;
  46                 static void *
  47                 thread_func (void *arg)
  48                 {
  49                   a_in_other_thread = &a;
  50                   return (void *)0;
  51                 }],
  52                [pthread_t thread;
  53                 void *thread_retval;
  54                 int *a_in_main_thread;
  55                 if (pthread_create (&thread, (pthread_attr_t *)0,
  56                                     thread_func, (void *)0))
  57                   return 0;
  58                 a_in_main_thread = &a;
  59                 if (pthread_join (thread, &thread_retval))
  60                   return 0;
  61                 return (a_in_other_thread == a_in_main_thread);])],
  62              [gcc_cv_have_tls=yes], [gcc_cv_have_tls=no], [])
  63           CFLAGS="$chktls_save_CFLAGS"
  64         fi
  65       fi],
  66       [gcc_cv_have_tls=no],
  67       [dnl This is the cross-compiling case. Assume libc supports TLS if the
  68        dnl binutils and the compiler do.
  69        AC_LINK_IFELSE([__thread int a; int b; int main() { return a = b; }],
  70          [chktls_save_LDFLAGS="$LDFLAGS"
  71           dnl Shared library options may depend on the host; this check
  72           dnl is only known to be needed for GNU/Linux.
  73           case $host in
  74             *-*-linux*)
  75               LDFLAGS="-shared -Wl,--no-undefined $LDFLAGS"
  76               ;;
  77           esac
  78           chktls_save_CFLAGS="$CFLAGS"
  79           CFLAGS="-fPIC $CFLAGS"
  80           dnl If -shared works, test if TLS works in a shared library.
  81           AC_LINK_IFELSE([int f() { return 0; }],
  82             [AC_LINK_IFELSE([__thread int a; int b; int f() { return a = b; }],
  83               [gcc_cv_have_tls=yes],
  84               [gcc_cv_have_tls=no])],
  85             [gcc_cv_have_tls=yes])
  86           CFLAGS="$chktls_save_CFLAGS"
  87           LDFLAGS="$chktls_save_LDFLAGS"], [gcc_cv_have_tls=no])
  88       ]
  89     )])
  90   if test "$enable_tls $gcc_cv_have_tls" = "yes yes"; then
  91     AC_DEFINE(HAVE_TLS, 1,
  92               [Define to 1 if the target supports thread-local storage.])
  93   fi])
  94
  95 dnl Check whether the target assembler supports TLS.
  96 AC_DEFUN([GCC_CHECK_CC_TLS], [
  97   GCC_ENABLE(tls, yes, [], [Use thread-local storage])
  98   AC_CACHE_CHECK([whether the target assembler supports thread-local storage],
  99                  gcc_cv_have_cc_tls, [
 100     AC_COMPILE_IFELSE([__thread int a; int b; int main() { return a = b; }],
 101       [gcc_cv_have_cc_tls=yes], [gcc_cv_have_cc_tls=no])]
 102     )])
 103   if test "$enable_tls $gcc_cv_have_cc_tls" = "yes yes"; then
 104     AC_DEFINE(HAVE_CC_TLS, 1,
 105               [Define to 1 if the target assembler supports thread-local storage.])
 106   fi])
 107
 108 dnl Check whether TLS is emulated.
 109 AC_DEFUN([GCC_CHECK_EMUTLS], [
 110   AC_CACHE_CHECK([whether the thread-local storage support is from emutls],
 111                  gcc_cv_use_emutls, [
 112     gcc_cv_use_emutls=no
 113     echo '__thread int a; int b; int main() { return a = b; }' > conftest.c
 114     if AC_TRY_COMMAND(${CC-cc} -Werror -S -o conftest.s conftest.c 1>&AS_MESSAGE_LOG_FD); then
 115       if grep __emutls_get_address conftest.s > /dev/null; then
 116         gcc_cv_use_emutls=yes
 117       fi
 118     fi
 119     rm -f conftest.*
 120     ])
 121   if test "$gcc_cv_use_emutls" = "yes" ; then
 122     AC_DEFINE(USE_EMUTLS, 1,
 123               [Define to 1 if the target use emutls for thread-local storage.])
 124   fi])