Guard memory block allocation.

2018-09-24  Martin Liska  <mliska@suse.cz>

	* memory-block.h (memory_block_pool::release): Annotate with
	valgrind that the memory is not accessible.

From-SVN: r264529

gcc/ChangeLog

 2018-09-24  Martin Liska  <mliska@suse.cz>
 
+	* memory-block.h (memory_block_pool::release): Annotate with
+	valgrind that the memory is not accessible.
+
+2018-09-24  Martin Liska  <mliska@suse.cz>
+
 	PR sanitizer/85774
 	* asan.c: Make asan_handled_variables extern.
 	* asan.h: Likewise.

gcc/memory-block.h

@@ -68,6 +68,11 @@ memory_block_pool::release (void *uncast_block)
   block_list *block = new (uncast_block) block_list;
   block->m_next = instance.m_blocks;
   instance.m_blocks = block;
+
+  VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS ((char *)uncast_block
+						+ sizeof (block_list),
+						block_size
+						- sizeof (block_list)));
 }
 
 extern void *mempool_obstack_chunk_alloc (size_t) ATTRIBUTE_MALLOC;