[libFuzzer][MSVC] Make attribute-use compatible with MSVC

[metzman]

Summary

Replace attributes with macros that use equivalent declspecs
for MSVC.

[metzman]

fix newlines

[metzman]

• fix

[metzman]

Please take a look Vitaly

[vitalybuka]

compiler-rt/lib/fuzzer/FuzzerDefs.h

133

what happend with __declspec(dllexport)

compiler-rt/lib/fuzzer/FuzzerInterface.h

32

why we don't use ATTRIBUTE_INTERFACE

[metzman]

• add dllexport back

[metzman]

• fix comment

[metzman]

• remove extra space

[metzman]

compiler-rt/lib/fuzzer/FuzzerDefs.h

133

Thanks for noticing this. I shouldn't have removed it and I added it back.

compiler-rt/lib/fuzzer/FuzzerInterface.h

32

Do you mean rename this ATTRIBUTE_INTERFACE? Or do you mean include FuzzerDefs.h and use that definition?
First seems 100% OK to do.
The second one I didn't do because this header is included by somethings that aren't part of libFuzzer and I didn't want to leak everything from FuzzerDefs.h to anything including FuzzerInterface.h.

I can do whichever you prefer.

41

I initially didn't set FUZZER_INTERFACE_VISIBILITY to dllexport on Windows since I felt weird about making these functions dllexport when they aren't even defined by libFuzzer.

There may be something I am missing here, but what do you think about removing FUZZER_INTERFACE_VISIBILITY from LLVMFuzzerInitialize, LLVMFuzzerCustomCrossOver, LLVMFuzzerCustomMutator?
What do they do here?

[vitalybuka]

LGTM

compiler-rt/lib/fuzzer/FuzzerDefs.h

 #  else
 #    define ATTRIBUTE_NO_SANITIZE_ALL
 #  endif
 #else
 #  define ATTRIBUTE_NO_SANITIZE_ALL
 #endif
 
 #if LIBFUZZER_WINDOWS
+#define ATTRIBUTE_ALIGNED(X) __declspec(align(X))
 #define ATTRIBUTE_INTERFACE __declspec(dllexport)
 // This is used for __sancov_lowest_stack which is needed for
 // -fsanitize-coverage=stack-depth. That feature is not yet available on
 // Windows, so make the symbol static to avoid linking errors.
 #define ATTRIBUTES_INTERFACE_TLS_INITIAL_EXEC \
   __attribute__((tls_model("initial-exec"))) thread_local static
+
+#define ATTRIBUTE_NOINLINE __declspec(noinline)
+#define ATTRIBUTE_NO_SANITIZE_ADDRESS
 #else
+#define ATTRIBUTE_ALIGNED(X) __attribute__((aligned(X)))
 #define ATTRIBUTE_INTERFACE __attribute__((visibility("default")))
 #define ATTRIBUTES_INTERFACE_TLS_INITIAL_EXEC \
   ATTRIBUTE_INTERFACE __attribute__((tls_model("initial-exec"))) thread_local
+
+#define ATTRIBUTE_NOINLINE __attribute__((noinline))
 #endif
 
 namespace fuzzer {
 
 template <class T> T Min(T a, T b) { return a < b ? a : b; }
 template <class T> T Max(T a, T b) { return a > b ? a : b; }
 
 class Random;

compiler-rt/lib/fuzzer/FuzzerDriver.cpp

 #include <cstdlib>
 #include <cstring>
 #include <mutex>
 #include <string>
 #include <thread>
 
 // This function should be present in the libFuzzer so that the client
 // binary can test for its existence.
+#if LIBFUZZER_MSVC
+extern "C" void __libfuzzer_is_present() {}
+#pragma comment(linker, "/include:__libfuzzer_is_present")
+#else
 extern "C" __attribute__((used)) void __libfuzzer_is_present() {}
+#endif  // LIBFUZZER_WINDOWS
 
 namespace fuzzer {
 
 // Program arguments.
 struct FlagDescription {
   const char *Name;
   const char *Description;
   int   Default;

compiler-rt/lib/fuzzer/FuzzerInterface.h

 
 #include <stddef.h>
 #include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif  // __cplusplus
 
+// Define FUZZER_INTERFACE_VISIBILITY to set default visibility in a way that
+// doesn't break MSVC.
+#if defined(_MSC_VER) && !defined(__clang__)
+#define FUZZER_INTERFACE_VISIBILITY
+#else
+#define FUZZER_INTERFACE_VISIBILITY __attribute__((visibility("default")))
+#endif
+
 // Mandatory user-provided target function.
 // Executes the code under test with [Data, Data+Size) as the input.
 // libFuzzer will invoke this function *many* times with different inputs.
 // Must return 0.
-__attribute__((visibility("default"))) int
+FUZZER_INTERFACE_VISIBILITY int
 LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
 
 // Optional user-provided initialization function.
 // If provided, this function will be called by libFuzzer once at startup.
 // It may read and modify argc/argv.
 // Must return 0.
-__attribute__((visibility("default"))) int LLVMFuzzerInitialize(int *argc,
-                                                                char ***argv);
+FUZZER_INTERFACE_VISIBILITY int LLVMFuzzerInitialize(int *argc, char ***argv);
 
 // Optional user-provided custom mutator.
 // Mutates raw data in [Data, Data+Size) inplace.
 // Returns the new size, which is not greater than MaxSize.
 // Given the same Seed produces the same mutation.
-__attribute__((visibility("default"))) size_t
+FUZZER_INTERFACE_VISIBILITY size_t
 LLVMFuzzerCustomMutator(uint8_t *Data, size_t Size, size_t MaxSize,
                         unsigned int Seed);
 
 // Optional user-provided custom cross-over function.
 // Combines pieces of Data1 & Data2 together into Out.
 // Returns the new size, which is not greater than MaxOutSize.
 // Should produce the same mutation given the same Seed.
-__attribute__((visibility("default"))) size_t
+FUZZER_INTERFACE_VISIBILITY size_t
 LLVMFuzzerCustomCrossOver(const uint8_t *Data1, size_t Size1,
                           const uint8_t *Data2, size_t Size2, uint8_t *Out,
                           size_t MaxOutSize, unsigned int Seed);
 
 // Experimental, may go away in future.
 // libFuzzer-provided function to be used inside LLVMFuzzerCustomMutator.
 // Mutates raw data in [Data, Data+Size) inplace.
 // Returns the new size, which is not greater than MaxSize.
-__attribute__((visibility("default"))) size_t
+FUZZER_INTERFACE_VISIBILITY size_t
 LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize);
 
+#undef FUZZER_INTERFACE_VISIBILITY
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif  // __cplusplus
 
 #endif  // LLVM_FUZZER_INTERFACE_H

compiler-rt/lib/fuzzer/FuzzerLoop.cpp

if (SMR.IsServer()) {
     }
   }
 }
 
 } // namespace fuzzer
 
 extern "C" {
 
-__attribute__((visibility("default"))) size_t
+ATTRIBUTE_INTERFACE size_t
 LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize) {
   assert(fuzzer::F);
   return fuzzer::F->GetMD().DefaultMutate(Data, Size, MaxSize);
 }
 
 // Experimental
-__attribute__((visibility("default"))) void
+ATTRIBUTE_INTERFACE void
 LLVMFuzzerAnnounceOutput(const uint8_t *Data, size_t Size) {
   assert(fuzzer::F);
   fuzzer::F->AnnounceOutput(Data, Size);
 }
 } // extern "C"

compiler-rt/lib/fuzzer/FuzzerMain.cpp

 
 #include "FuzzerDefs.h"
 
 extern "C" {
 // This function should be defined by the user.
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
 }  // extern "C"
 
-__attribute__((visibility("default"))) int main(int argc, char **argv) {
+ATTRIBUTE_INTERFACE int main(int argc, char **argv) {
   return fuzzer::FuzzerDriver(&argc, &argv, LLVMFuzzerTestOneInput);
 }

compiler-rt/lib/fuzzer/FuzzerTracePC.h

unsigned CounterToFeature(T Counter) {
     else if (Counter >= 4) Bit = 3;
     else if (Counter >= 3) Bit = 2;
     else if (Counter >= 2) Bit = 1;
     return Bit;
 }
 
 template <class Callback>  // void Callback(size_t Feature)
 ATTRIBUTE_NO_SANITIZE_ADDRESS
-__attribute__((noinline))
+ATTRIBUTE_NOINLINE
 void TracePC::CollectFeatures(Callback HandleFeature) const {
   uint8_t *Counters = this->Counters();
   size_t N = GetNumPCs();
   auto Handle8bitCounter = [&](size_t FirstFeature,
                                size_t Idx, uint8_t Counter) {
     if (UseCounters)
       HandleFeature(FirstFeature + Idx * 8 + CounterToFeature(Counter));
     else

compiler-rt/lib/fuzzer/FuzzerValueBitMap.h

void ForEach(Callback CB) const {
     for (size_t i = 0; i < kMapSizeInWords; i++)
       if (uintptr_t M = Map[i])
         for (size_t j = 0; j < sizeof(M) * 8; j++)
           if (M & ((uintptr_t)1 << j))
             CB(i * sizeof(M) * 8 + j);
   }
 
  private:
-  uintptr_t Map[kMapSizeInWords] __attribute__((aligned(512)));
+  ATTRIBUTE_ALIGNED(512) uintptr_t Map[kMapSizeInWords];
 };
 
 }  // namespace fuzzer
 
 #endif  // LLVM_FUZZER_VALUE_BIT_MAP_H