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 withdnl static linking. This fails at least with some older Red Hatdnl 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"; thenAC_DEFINE(HAVE_TLS, 1,[Define to 1 if the target supports thread-local storage.])fi])