Merge remote-tracking branch 'upstream/dev' into ldm-mergeDev

lib/common/pool.c

@@ -236,7 +236,7 @@ POOL_ctx* POOL_create_advanced(size_t numThreads, size_t queueSize, ZSTD_customM
 }
 
 void POOL_free(POOL_ctx* ctx) {
-    assert(ctx == &g_ctx);
+    assert(!ctx || ctx == &g_ctx);
     (void)ctx;
 }
 

lib/common/threading.c

@@ -14,12 +14,8 @@
  * This file will hold wrapper for systems, which do not support pthreads
  */
 
-/* When ZSTD_MULTITHREAD is not defined, this file would become an empty translation unit.
- * Include some ISO C header code to prevent this and portably avoid related warnings.
- * (Visual C++: C4206 / GCC: -Wpedantic / Clang: -Wempty-translation-unit)
- */
-#include <stddef.h>
-
+/* create fake symbol to avoid empty trnaslation unit warning */
+int g_ZSTD_threading_useles_symbol;
 
 #if defined(ZSTD_MULTITHREAD) && defined(_WIN32)