diff options
Diffstat (limited to 'm4/tls.m4')
| -rw-r--r-- | m4/tls.m4 | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/m4/tls.m4 b/m4/tls.m4 new file mode 100644 index 0000000..d2243aa --- /dev/null +++ b/m4/tls.m4 @@ -0,0 +1,111 @@ +# +# AX_CHECK_TLS -- check whether the target supports TLS (thread-local storage) +# +# Based on tls.m4 from gcc and extended by TLS link test for cross-compiling +# support from http://old.nabble.com/Improve-TLS-link-test-for-cross-compiling-td24312975.html +# +# Note that AX_TLS from http://autoconf-archive.cryp.to/ax_tls.html supports +# more keywords for TLS. We are happy with the "__thread" only. +# +# -- Karel Zak (04-Dec-2009) +# +dnl Check whether the target supports TLS. +AC_DEFUN([AX_CHECK_TLS], [ + + AC_REQUIRE([AC_CANONICAL_HOST]) + + AC_ARG_ENABLE([tls], + AS_HELP_STRING([--disable-tls], [disable use of thread local support]), + [], enable_tls=yes) + + AC_CACHE_CHECK([whether the target supports thread-local storage], + ax_cv_have_tls, [ + AC_RUN_IFELSE([AC_LANG_SOURCE([__thread int a; int b; int main() { return a = b; }])], + [dnl If the test case passed with dynamic linking, try again with + dnl static linking, but only if static linking is supported (not + dnl on Solaris 10). This fails with some older Red Hat releases. + chktls_save_LDFLAGS="$LDFLAGS" + LDFLAGS="-static $LDFLAGS" + AC_LINK_IFELSE([AC_LANG_SOURCE([int main() { return 0; }])], + AC_RUN_IFELSE([AC_LANG_SOURCE([__thread int a; int b; int main() { return a = b; }])], + [ax_cv_have_tls=yes], [ax_cv_have_tls=no],[]), + [ax_cv_have_tls=yes]) + LDFLAGS="$chktls_save_LDFLAGS" + if test $ax_cv_have_tls = yes; then + dnl So far, the binutils and the compiler support TLS. + dnl Also check whether the libc supports TLS, i.e. whether a variable + dnl with __thread linkage has a different address in different threads. + dnl First, find the thread_CFLAGS necessary for linking a program that + dnl calls pthread_create. + chktls_save_CFLAGS="$CFLAGS" + thread_CFLAGS=failed + for flag in '' '-pthread' '-lpthread'; do + CFLAGS="$flag $chktls_save_CFLAGS" + AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [#include <pthread.h> + void *g(void *d) { return NULL; }], + [pthread_t t; pthread_create(&t,NULL,g,NULL);])], + [thread_CFLAGS="$flag"]) + if test "X$thread_CFLAGS" != Xfailed; then + break + fi + done + CFLAGS="$chktls_save_CFLAGS" + if test "X$thread_CFLAGS" != Xfailed; then + CFLAGS="$thread_CFLAGS $chktls_save_CFLAGS" + AC_RUN_IFELSE( + [AC_LANG_PROGRAM( + [#include <pthread.h> + __thread int a; + static int *a_in_other_thread; + static void * + thread_func (void *arg) + { + a_in_other_thread = &a; + return (void *)0; + }], + [pthread_t thread; + void *thread_retval; + int *a_in_main_thread; + if (pthread_create (&thread, (pthread_attr_t *)0, + thread_func, (void *)0)) + return 0; + a_in_main_thread = &a; + if (pthread_join (thread, &thread_retval)) + return 0; + return (a_in_other_thread == a_in_main_thread);])], + [ax_cv_have_tls=yes], [ax_cv_have_tls=no], []) + CFLAGS="$chktls_save_CFLAGS" + fi + fi], + [ax_cv_have_tls=no], + [dnl This is the cross-compiling case. Assume libc supports TLS if the + dnl binutils and the compiler do. + AC_LINK_IFELSE([AC_LANG_SOURCE([__thread int a; int b; int main() { return a = b; }])], + [chktls_save_LDFLAGS="$LDFLAGS" + dnl Shared library options may depend on the host; this check + dnl is only known to be needed for GNU/Linux. + case $host in + *-*-linux*) + LDFLAGS="-shared -Wl,--no-undefined $LDFLAGS" + ;; + esac + chktls_save_CFLAGS="$CFLAGS" + CFLAGS="-fPIC $CFLAGS" + dnl If -shared works, test if TLS works in a shared library. + AC_LINK_IFELSE([AC_LANG_SOURCE([int f() { return 0; }])], + [AC_LINK_IFELSE([AC_LANG_SOURCE([__thread int a; int b; int f() { return a = b; }])], + [ax_cv_have_tls=yes], + [ax_cv_have_tls=no])], + [ax_cv_have_tls=yes]) + CFLAGS="$chktls_save_CFLAGS" + LDFLAGS="$chktls_save_LDFLAGS"], [ax_cv_have_tls=no]) + ] + )]) + + if test "$enable_tls $ax_cv_have_tls" = "yes yes"; then + AC_DEFINE(HAVE_TLS, 1, + [Define to 1 if the target supports thread-local storage.]) + fi +]) |