Index: lib/asan/tests/CMakeLists.txt
===================================================================
--- lib/asan/tests/CMakeLists.txt
+++ lib/asan/tests/CMakeLists.txt
@@ -34,6 +34,13 @@
   -O2)
 append_if(ASAN_UNITTEST_COMMON_CFLAGS COMPILER_RT_HAS_WNO_VARIADIC_MACROS_FLAG -Wno-variadic-macros)
 
+# System headers incorrectly define 'size_t' as 'unsigned long' on
+# x64 FreeBSD 9.2 whereas 'unsigned int' is expected.
+if(CMAKE_SYSTEM MATCHES "FreeBSD-9.2-RELEASE" AND
+    CMAKE_SIZEOF_VOID_P MATCHES "8")
+  list(APPEND ASAN_UNITTEST_COMMON_CFLAGS -D_SIZE_T_DECLARED)
+endif()
+
 # Use -D instead of definitions to please custom compile command.
 list(APPEND ASAN_UNITTEST_COMMON_CFLAGS
   -DASAN_HAS_BLACKLIST=1