[llvm] r257423 - [libFuzzer] extend the weak memcmp/strcmp/strncmp interceptors to receive the result of the computations. With that, don't do any mutations if memcmp/etc returned 0

[Kostya Serebryany via llvm-commits]

Author: kcc
Date: Mon Jan 11 18:43:42 2016
New Revision: 257423

URL: http://llvm.org/viewvc/llvm-project?rev=257423&view=rev
Log:
[libFuzzer] extend the weak memcmp/strcmp/strncmp interceptors to receive the result of the computations. With that, don't do any mutations if memcmp/etc returned 0

Modified:
    llvm/trunk/lib/Fuzzer/FuzzerTraceState.cpp

Modified: llvm/trunk/lib/Fuzzer/FuzzerTraceState.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Fuzzer/FuzzerTraceState.cpp?rev=257423&r1=257422&r2=257423&view=diff
==============================================================================
--- llvm/trunk/lib/Fuzzer/FuzzerTraceState.cpp (original)
+++ llvm/trunk/lib/Fuzzer/FuzzerTraceState.cpp Mon Jan 11 18:43:42 2016
@@ -539,16 +539,18 @@ void dfsan_weak_hook_strcmp(void *caller
 }
 
 void __sanitizer_weak_hook_memcmp(void *caller_pc, const void *s1,
-                                  const void *s2, size_t n) {
+                                  const void *s2, size_t n, int result) {
   if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
   if (n <= 1) return;  // Not interesting.
   TS->TraceMemcmpCallback(n, reinterpret_cast<const uint8_t *>(s1),
                           reinterpret_cast<const uint8_t *>(s2));
 }
 
 void __sanitizer_weak_hook_strncmp(void *caller_pc, const char *s1,
-                                   const char *s2, size_t n) {
+                                   const char *s2, size_t n, int result) {
   if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
   size_t Len1 = fuzzer::InternalStrnlen(s1, n);
   size_t Len2 = fuzzer::InternalStrnlen(s2, n);
   n = std::min(n, Len1);
@@ -559,8 +561,9 @@ void __sanitizer_weak_hook_strncmp(void
 }
 
 void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
-                                   const char *s2) {
+                                   const char *s2, int result) {
   if (!TS) return;
+  if (result == 0) return;  // No reason to mutate.
   size_t Len1 = strlen(s1);
   size_t Len2 = strlen(s2);
   size_t N = std::min(Len1, Len2);