[ASan] Add the memcmp_strict flag (1 by default) that controls the behavior of accessibility checks in memcmp.

1: memcmp(p1, p2, n) always checks n bytes
0: memcmp checks up to n bytes depending on whether the memory contents differ.

llvm-svn: 176256

1 files changed, 2 insertions, 0 deletions

diff --git a/compiler-rt/lib/asan/asan_rtl.cc b/compiler-rt/lib/asan/asan_rtl.cc
index 770e93a5843..d7aebd47842 100644
--- a/compiler-rt/lib/asan/asan_rtl.cc
+++ b/compiler-rt/lib/asan/asan_rtl.cc
@@ -127,6 +127,7 @@ static void ParseFlagsFromString(Flags *f, const char *str) {
   ParseFlag(str, &f->poison_heap, "poison_heap");
   ParseFlag(str, &f->alloc_dealloc_mismatch, "alloc_dealloc_mismatch");
   ParseFlag(str, &f->use_stack_depot, "use_stack_depot");
+  ParseFlag(str, &f->strict_memcmp, "strict_memcmp");
 }
 
 void InitializeFlags(Flags *f, const char *env) {
@@ -168,6 +169,7 @@ void InitializeFlags(Flags *f, const char *env) {
   // TODO(glider): Fix known issues and enable this back.
   f->alloc_dealloc_mismatch = (ASAN_MAC == 0);;
   f->use_stack_depot = true;  // Only affects allocator2.
+  f->strict_memcmp = true;
 
   // Override from compile definition.
   ParseFlagsFromString(f, MaybeUseAsanDefaultOptionsCompileDefiniton());