Create a new macro for checking compiler support for TLS.

Create a new macro that can be shared between projects to check for
__thread support by the compiler. This macro might come useful for
xine-lib too so I want to keep it separate for easier importing it
over.

Name the defined macro SUPPORT_TLS___THREAD to follow the same style
as the checks from attributes.m4.

1 files changed, 17 insertions, 0 deletions

diff --git a/m4/tls.m4 b/m4/tls.m4
new file mode 100644
index 00000000..3808f06e
--- /dev/null
+++ b/m4/tls.m4
@@ -0,0 +1,17 @@
+AC_DEFUN([CC_CHECK_TLS], [
+  AC_CACHE_CHECK([whether $CC knows __thread for Thread-Local Storage],
+    cc_cv_tls___thread,
+    [AC_COMPILE_IFELSE(
+      AC_LANG_PROGRAM(
+        [[static __thread int a = 6;]],
+        [[a = 5;]]),
+      [cc_cv_tls___thread=yes],
+      [cc_cv_tls___thread=no])
+    ])
+  
+  AS_IF([test "x$cc_cv_tls___thread" = "xyes"],
+    [AC_DEFINE([SUPPORT_TLS___THREAD], 1,
+     [Define this if the compiler supports __thread for Thread-Local Storage])
+     $1],
+    [$2])
+])