Marking exported symbols as visible.

[aizatsky]

Summary

Without default visibility there's error while compiling libfuzzer in chrome:

../../third_party/binutils/Linux_x64/Release/bin/ld.gold: warning: hidden symbol 'sanitizer_cov_trace_switch' in obj/testing/libfuzzer/libfuzzer_main.a(FuzzerTraceState.o) is referenced by DSO ./libc++.so
../../third_party/binutils/Linux_x64/Release/bin/ld.gold: warning: Cannot export local symbol 'sanitizer_cov_trace_switch'

Similar issue: https://code.google.com/p/chromium/issues/detail?id=368351

[kcc]

Is this testable within libFuzzer?
(please CC llvm-commits to libFuzzer patches)

[aizatsky]

Is this testable within libFuzzer?

This breaks in chrome because linker is stricter in chrome. It doesn't allow reexporting of private symbols there.

[kcc]

LGTM

[kcc]

r248954.

lib/Fuzzer/FuzzerTraceState.cpp

void __sanitizer_weak_hook_strcmp(void *caller_pc, const char *s1,
   size_t N = std::min(Len1, Len2);
   if (N <= 1) return;  // Not interesting.
   // Simplification: handle only first 8 bytes.
   memcpy(&S1, s1, std::min(N, sizeof(S1)));
   memcpy(&S2, s2, std::min(N, sizeof(S2)));
   TS->TraceCmpCallback(PC, N, fuzzer::ICMP_EQ, S1, S2);
 }
 
-
+__attribute__((visibility("default")))
 void __sanitizer_cov_trace_cmp(uint64_t SizeAndType, uint64_t Arg1,
                                uint64_t Arg2) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   uint64_t CmpSize = (SizeAndType >> 32) / 8;
   uint64_t Type = (SizeAndType << 32) >> 32;
   TS->TraceCmpCallback(PC, CmpSize, Type, Arg1, Arg2);
 }
 
+__attribute__((visibility("default")))
 void __sanitizer_cov_trace_switch(uint64_t Val, uint64_t *Cases) {
   if (!TS) return;
   uintptr_t PC = reinterpret_cast<uintptr_t>(__builtin_return_address(0));
   TS->TraceSwitchCallback(PC, Cases[1], Val, Cases[0], Cases + 2);
 }
 
 }  // extern "C"