[fuzzer] Replace FuzzerExtFunctionsDlsymWin.cpp with FuzzerExtFunctionsWeakAlias.cpp

[metzman]

Summary

Replace FuzzerExtFunctionsDlsymWin.cpp with FuzzerExtFunctionsWeakAlias.cpp
to get externally defined functions (eg: LLVMFuzzerInitialize,
LLVMFuzzerCustomMutator, etc) working again.

Also enable tests that depended on these functions (on windows)

[metzman]

@morehouse and @rnk: please take a look.

My patch essentially undoes this one by Marcos.
I can't tell for sure what problem that patch solved and I haven't been able to reproduce it.
I think that maybe the use of -fsanitize=fuzzer has made it so that the issue seen no longer appears.
I've tested many chrome fuzzers with my patch and the initial code, the initial code does not work for loading functions like LLVMFuzzerInitialize etc. in non-component (ie: MT) builds, whereas with my patch these functions are found.
This change might break (more than it already is broken) MD builds but I don't need this for Chrome and I think it makes most sense to get one kind of build fully working rather than having neither kind fully working.

[metzman]

Should I remove FuzzerExtFunctionsDlsymWin.cpp?
I'm unsure about doing so because in Marcos's patch he didn't remove FuzzerExtFunctionsWeakAlias.cpp and because I may find how use it properly later, in which case removing it might make the history uglier?

[morehouse]

LGTM

[rnk]

lgtm

[rnk]

In D51700#1236413, @metzman wrote:

Should I remove FuzzerExtFunctionsDlsymWin.cpp?
I'm unsure about doing so because in Marcos's patch he didn't remove FuzzerExtFunctionsWeakAlias.cpp and because I may find how use it properly later, in which case removing it might make the history uglier?

Missed this initially... I would go ahead and remove it.

[metzman]

• Remove unused file.

lib/fuzzer/CMakeLists.txt

 set(LIBFUZZER_SOURCES
   FuzzerCrossOver.cpp
   FuzzerDataFlowTrace.cpp
   FuzzerDriver.cpp
   FuzzerExtFunctionsDlsym.cpp
-  FuzzerExtFunctionsDlsymWin.cpp
+  FuzzerExtFunctionsWeakAlias.cpp
   FuzzerExtFunctionsWeak.cpp
   FuzzerExtraCounters.cpp
   FuzzerIO.cpp
   FuzzerIOPosix.cpp
   FuzzerIOWindows.cpp
   FuzzerLoop.cpp
   FuzzerMerge.cpp
   FuzzerMutate.cpp

lib/fuzzer/FuzzerExtFunctionsDlsymWin.cpp

-//===- FuzzerExtFunctionsDlsymWin.cpp - Interface to external functions ---===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-// Implementation using dynamic loading for Windows.
-//===----------------------------------------------------------------------===//
-#include "FuzzerDefs.h"
-#if LIBFUZZER_WINDOWS
-
-#include "FuzzerExtFunctions.h"
-#include "FuzzerIO.h"
-#include <windows.h>
-
-// This must be included after Windows.h.
-#include <psapi.h>
-
-namespace fuzzer {
-
-ExternalFunctions::ExternalFunctions() {
-  HMODULE Modules[1024];
-  DWORD BytesNeeded;
-  HANDLE CurrentProcess = GetCurrentProcess();
-
-  if (!EnumProcessModules(CurrentProcess, Modules, sizeof(Modules),
-                          &BytesNeeded)) {
-    Printf("EnumProcessModules failed (error: %d).\n", GetLastError());
-    exit(1);
-  }
-
-  if (sizeof(Modules) < BytesNeeded) {
-    Printf("Error: the array is not big enough to hold all loaded modules.\n");
-    exit(1);
-  }
-
-  for (size_t i = 0; i < (BytesNeeded / sizeof(HMODULE)); i++)
-  {
-    FARPROC Fn;
-#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)                            \
-    if (this->NAME == nullptr) {                                               \
-      Fn = GetProcAddress(Modules[i], #NAME);                                  \
-      if (Fn == nullptr)                                                       \
-         Fn = GetProcAddress(Modules[i], #NAME "__dll");                       \
-      this->NAME = (decltype(ExternalFunctions::NAME)) Fn;                     \
-    }
-#include "FuzzerExtFunctions.def"
-#undef EXT_FUNC
-  }
-
-#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)                            \
-  if (this->NAME == nullptr && WARN)                                           \
-    Printf("WARNING: Failed to find function \"%s\".\n", #NAME);
-#include "FuzzerExtFunctions.def"
-#undef EXT_FUNC
-}
-
-} // namespace fuzzer
-
-#endif // LIBFUZZER_WINDOWS

test/fuzzer/bogus-initialize.test

-# FIXME: Disabled on Windows since LLVMFuzzerInitialize does not yet work.
-UNSUPPORTED: windows
 RUN: %cpp_compiler %S/BogusInitializeTest.cpp -o %t-BogusInitializeTest
 
 RUN: not %run %t-BogusInitializeTest 2>&1 | FileCheck %s --check-prefix=BOGUS_INITIALIZE
 BOGUS_INITIALIZE: argv[0] has been modified in LLVMFuzzerInitialize

test/fuzzer/fuzzer-customcrossover.test

-# FIXME: Disabled on Windows since LLVMFuzzerCustomCrossOver does not yet work.
-UNSUPPORTED: windows
 RUN: %cpp_compiler %S/CustomCrossOverTest.cpp -o %t-CustomCrossOverTest
 
 RUN: not %run %t-CustomCrossOverTest -seed=1 -runs=1000000                2>&1 | FileCheck %s --check-prefix=CHECK_CO
 Disable cross_over, verify that we can't find the target w/o it.
 RUN:     %run %t-CustomCrossOverTest -seed=1 -runs=1000000 -cross_over=0 2>&1 | FileCheck %s --check-prefix=CHECK_NO_CO
 
 CHECK_CO: In LLVMFuzzerCustomCrossover
 CHECK_CO: BINGO
 
 CHECK_NO_CO-NO: LLVMFuzzerCustomCrossover
 CHECK_NO_CO: DONE
 

test/fuzzer/fuzzer-custommutator.test

-# FIXME: Disabled on Windows since LLVMFuzzerCustomMutator does not yet work.
-UNSUPPORTED: windows
 RUN: %cpp_compiler %S/CustomMutatorTest.cpp -o %t-CustomMutatorTest
 RUN: not %run %t-CustomMutatorTest 2>&1 | FileCheck %s --check-prefix=LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutator: In LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutator: BINGO
 

test/fuzzer/fuzzer-flags.test

-# FIXME: Disabled on Windows since LLVMFuzzerInitialize does not yet work.
-UNSUPPORTED: windows
-RUN: %cpp_compiler %S/FlagsTest.cpp -o %t-FlagsTest
 RUN: %run %t-FlagsTest -runs=10 -foo_bar=1 2>&1 | FileCheck %s --check-prefix=FOO_BAR
 FOO_BAR: WARNING: unrecognized flag '-foo_bar=1'; use -help=1 to list all flags
 FOO_BAR: BINGO
 
 RUN: %run %t-FlagsTest -runs=10 --max_len=100 2>&1 | FileCheck %s --check-prefix=DASH_DASH
 DASH_DASH: WARNING: did you mean '-max_len=100' (single dash)?
 DASH_DASH: INFO: A corpus is not provided, starting from an empty corpus
 

test/fuzzer/initialize.test

-# FIXME: Disabled on Windows since LLVMFuzzerInitialize does not yet work.
-UNSUPPORTED: windows
 CHECK: BINGO
 RUN: %cpp_compiler %S/InitializeTest.cpp -o %t-InitializeTest
 RUN: not %run %t-InitializeTest -use_value_profile=1 2>&1 | FileCheck %s

test/fuzzer/standalone.test

-# FIXME: Disabled on Windows because memmem is a GNU extension.
-UNSUPPORTED: windows
 RUN: %no_fuzzer_c_compiler %libfuzzer_src/standalone/StandaloneFuzzTargetMain.c -c -o %t_1.o
 RUN: %no_fuzzer_cpp_compiler %S/InitializeTest.cpp -c -o %t_2.o
 
 RUN: %no_fuzzer_cpp_compiler %t_1.o %t_2.o -o %t-StandaloneInitializeTest
 RUN: %run %t-StandaloneInitializeTest %S/hi.txt %S/dict1.txt 2>&1 | FileCheck %s
 CHECK: StandaloneFuzzTargetMain: running 2 inputs
 CHECK: Done:    {{.*}}hi.txt: (3 bytes)
 CHECK: Done:    {{.*}}dict1.txt: (61 bytes)