[SCM] libav/experimental: threads: Check w32threads dependencies at the configure stage

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit 874c751cc5b99cd68932e21c2c3a0d21134207e0
Author: Diego Biurrun <diego at biurrun.de>
Date:   Wed Dec 18 22:29:25 2013 +0100

    threads: Check w32threads dependencies at the configure stage
    
    Also add warning comment about threading implementations without matching
    atomics implementation to the atomics fallback implementation.

diff --git a/configure b/configure
index 292da47..841c39a 100755
--- a/configure
+++ b/configure
@@ -1606,6 +1606,7 @@ atomics_gcc_if="sync_val_compare_and_swap"
 atomics_suncc_if="atomic_cas_ptr machine_rw_barrier"
 atomics_win32_if="MemoryBarrier"
 atomics_native_if_any="$ATOMICS_LIST"
+w32threads_deps="atomics_native"
 threads_if_any="$THREADS_LIST"
 
 # subsystems
diff --git a/libavutil/atomic.c b/libavutil/atomic.c
index e4fa957..8374039 100644
--- a/libavutil/atomic.c
+++ b/libavutil/atomic.c
@@ -97,8 +97,11 @@ void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval)
     return *ptr;
 }
 
-#else
+#else /* HAVE_THREADS */
 
+/* This should never trigger, unless a new threading implementation
+ * without correct atomics dependencies in configure or a corresponding
+ * atomics implementation is added. */
 #error "Threading is enabled, but there is no implementation of atomic operations available"
 
 #endif /* HAVE_PTHREADS */

-- 
Libav/FFmpeg packaging