[PATCH] disable lock annotation with clang 3.4.2

[David Marchand <david.marchand@redhat.com>]

Venerable RHEL7 clang 3.4.2 has (at least) two issues with lock
annotations.

A first one with regards to the attribute position:
../lib/vhost/vhost.h:518:2: error: GCC does not allow
	assert_exclusive_lock attribute in this position on a
	function definition [-Werror,-Wgcc-compat]
        __rte_assert_exclusive_lock(&vq->access_lock)
        ^
../lib/eal/include/rte_lock_annotations.h:29:38: note: expanded
	from macro '__rte_assert_exclusive_lock'
        __attribute__((assert_exclusive_lock(__VA_ARGS__)))
                                            ^

This can be worked around by splitting and having the allocation on the
function declaration.

But on the other hand, clang 3.4.2 does not seem to propagate those
annotations in presence of a __builtin_expect (i.e. unlikely()), like
for example when calling if (unlikely(rte_spinlock_trylock() == 0)).

Those annotations were only working with clang in any case, so restrict
to clang versions newer than 3.5.0.

Fixes: 657a98f38940 ("eal: annotate spinlock, rwlock and seqlock")

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
 drivers/meson.build | 2 +-
 lib/meson.build     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/meson.build b/drivers/meson.build
index bddc4a6cc4..0618c31a69 100644
--- a/drivers/meson.build
+++ b/drivers/meson.build
@@ -168,7 +168,7 @@ foreach subpath:subdirs
         enabled_drivers += name
         lib_name = '_'.join(['rte', class, name])
         cflags += '-DRTE_LOG_DEFAULT_LOGTYPE=' + '.'.join([log_prefix, name])
-        if annotate_locks and cc.has_argument('-Wthread-safety')
+        if annotate_locks and cc.get_id() == 'clang' and cc.version().version_compare('>=3.5.0')
             cflags += '-DRTE_ANNOTATE_LOCKS'
             cflags += '-Wthread-safety'
         endif
diff --git a/lib/meson.build b/lib/meson.build
index 450c061d2b..2bc0932ad5 100644
--- a/lib/meson.build
+++ b/lib/meson.build
@@ -203,7 +203,7 @@ foreach l:libraries
         cflags += '-DRTE_USE_FUNCTION_VERSIONING'
     endif
     cflags += '-DRTE_LOG_DEFAULT_LOGTYPE=lib.' + l
-    if annotate_locks and cc.has_argument('-Wthread-safety')
+    if annotate_locks and cc.get_id() == 'clang' and cc.version().version_compare('>=3.5.0')
         cflags += '-DRTE_ANNOTATE_LOCKS'
         cflags += '-Wthread-safety'
     endif
-- 
2.39.1