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dnl Check whether the target supports TLS.
AC_DEFUN([GCC_CHECK_TLS], [
GCC_ENABLE(tls, yes, [], [Use thread-local storage])
AC_CACHE_CHECK([whether the target supports thread-local storage],
have_tls, [
AC_RUN_IFELSE([__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. This fails at least with some older Red Hat
dnl releases.
save_LDFLAGS="$LDFLAGS"
LDFLAGS="-static $LDFLAGS"
AC_RUN_IFELSE([__thread int a; int b; int main() { return a = b; }],
[have_tls=yes], [have_tls=no], [])
LDFLAGS="$save_LDFLAGS"],
[have_tls=no],
[AC_COMPILE_IFELSE([__thread int foo;], [have_tls=yes], [have_tls=no])]
)])
if test "$enable_tls $have_tls" = "yes yes"; then
AC_DEFINE(HAVE_TLS, 1,
[Define to 1 if the target supports thread-local storage.])
fi])
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