[PATCH v2] glx: Silence warnings when building with clang

[Jeremy Huddleston]

In file included from glapi.c:46:
In file included from ./glapi.h:51:
./glthread.h:237:20: error: unknown attribute 'tls_model' ignored [-Werror,-Wunknown-attributes]
    __attribute__((tls_model("initial-exec")));
                   ^
In file included from glapi.c:46:
./glapi.h:92:20: error: unknown attribute 'tls_model' ignored [-Werror,-Wunknown-attributes]
    __attribute__((tls_model("initial-exec")));
                   ^
glapi.c:82:20: error: unknown attribute 'tls_model' ignored [-Werror,-Wunknown-attributes]
    __attribute__((tls_model("initial-exec"))) = NULL;
                   ^
glapi.c:85:20: error: unknown attribute 'tls_model' ignored [-Werror,-Wunknown-attributes]
    __attribute__((tls_model("initial-exec")));
                   ^
4 errors generated.

Signed-off-by: Jeremy Huddleston <jeremyhu at apple.com>
---
 configure.ac            |   21 +++++++++++++++++++++
 glx/glapi.c             |    6 ++----
 glx/glapi.h             |    3 +--
 glx/glthread.h          |    3 +--
 include/dix-config.h.in |    3 +++
 5 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/configure.ac b/configure.ac
index 86e67f0..974861b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -590,7 +590,28 @@ dnl GLX build options
 AC_ARG_ENABLE(aiglx,          AS_HELP_STRING([--enable-aiglx], [Build accelerated indirect GLX (default: enabled)]),
                                 [AIGLX=$enableval],
                                 [AIGLX=yes])
+
 AX_TLS
+if test "$ac_cv_tls" != "none"; then
+  AC_MSG_CHECKING(if thread local storage (TLS) class supports the tls_model attribute)
+
+  AC_CACHE_VAL(ac_cv_tls_model, [
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$CFLAGS -Werror=unknown-attributes"
+    AC_TRY_COMPILE([], [TLS int bar __attribute__((tls_model("initial-exec")));],
+                   ac_cv_tls_model=yes, ac_cv_tls_model=no)
+    CFLAGS="$save_CFLAGS"
+  ])
+
+  AC_MSG_RESULT($ac_cv_tls_model)
+
+  ac_tls_initial_exec="$ac_cv_tls"
+  if test "x$ac_cv_tls_model" = "xyes" ; then
+    ac_tls_initial_exec="$ac_tls_initial_exec __attribute__((tls_model("initial-exec")))"
+  fi
+  AC_DEFINE_UNQUOTED([TLS_MODEL_INITIAL_EXEC], $ac_tls_initial_exec, [If the compiler supports the tls_model attribute, we prefer initial-exec])
+fi
+
 AC_ARG_ENABLE(glx-tls,        AS_HELP_STRING([--enable-glx-tls], [Build GLX with TLS support (default: auto)]),
                                 [GLX_USE_TLS=$enableval
                                  if test "x$GLX_USE_TLS" = "xyes" && test "${ac_cv_tls}" = "none" ; then
diff --git a/glx/glapi.c b/glx/glapi.c
index 7cb8495..7ffffc2 100644
--- a/glx/glapi.c
+++ b/glx/glapi.c
@@ -78,11 +78,9 @@ static void init_glapi_relocs(void);
 /*@{*/
 #if defined(GLX_USE_TLS)
 
-PUBLIC TLS struct _glapi_table * _glapi_tls_Dispatch
-    __attribute__((tls_model("initial-exec"))) = NULL;
+PUBLIC TLS_MODEL_INITIAL_EXEC struct _glapi_table * _glapi_tls_Dispatch = NULL;
 
-PUBLIC TLS void * _glapi_tls_Context
-    __attribute__((tls_model("initial-exec")));
+PUBLIC TLS_MODEL_INITIAL_EXEC void * _glapi_tls_Context;
 
 PUBLIC const struct _glapi_table *_glapi_Dispatch = NULL;
 PUBLIC const void *_glapi_Context = NULL;
diff --git a/glx/glapi.h b/glx/glapi.h
index 6521f31..f837ef4 100644
--- a/glx/glapi.h
+++ b/glx/glapi.h
@@ -83,8 +83,7 @@ typedef void (*_glapi_warning_func)(void *ctx, const char *str, ...);
 const extern void *_glapi_Context;
 const extern struct _glapi_table *_glapi_Dispatch;
 
-extern TLS void * _glapi_tls_Context
-    __attribute__((tls_model("initial-exec")));
+extern TLS_MODEL_INITIAL_EXEC void * _glapi_tls_Context;
 
 # define GET_CURRENT_CONTEXT(C)  GLcontext *C = (GLcontext *) _glapi_tls_Context
 
diff --git a/glx/glthread.h b/glx/glthread.h
index 140e2aa..c558926 100644
--- a/glx/glthread.h
+++ b/glx/glthread.h
@@ -233,8 +233,7 @@ _glthread_SetTSD(_glthread_TSD *, void *);
 
 #if defined(GLX_USE_TLS)
 
-extern TLS struct _glapi_table * _glapi_tls_Dispatch
-    __attribute__((tls_model("initial-exec")));
+extern TLS_MODEL_INITIAL_EXEC struct _glapi_table * _glapi_tls_Dispatch;
 
 #define GET_DISPATCH() _glapi_tls_Dispatch
 
diff --git a/include/dix-config.h.in b/include/dix-config.h.in
index f00c767..9b2f053 100644
--- a/include/dix-config.h.in
+++ b/include/dix-config.h.in
@@ -447,6 +447,9 @@
 /* If the compiler supports a TLS storage class define it to that here */
 #undef TLS
 
+/* If the compiler supports the tls_model attribute, we prefer initial-exec */
+#undef TLS_MODEL_INITIAL_EXEC
+
 /* Correctly set _XSERVER64 for OSX fat binaries */
 #ifdef __APPLE__
 #include "dix-config-apple-verbatim.h"
-- 
1.7.4.1