//=== FuzzerExtWindows.cpp - Interface to external functions --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// Implementation of FuzzerExtFunctions for Windows. Uses alternatename when
// compiled with MSVC. Uses weak aliases when compiled with clang. Unfortunately
// the method each compiler supports is not supported by the other.
//===----------------------------------------------------------------------===//
#include "FuzzerPlatform.h"
#if LIBFUZZER_WINDOWS

  #include "FuzzerExtFunctions.h"
  #include "FuzzerIO.h"

using namespace fuzzer;

  // Intermediate macro to ensure the parameter is expanded before stringified.
  #define STRINGIFY_(A) #A
  #define STRINGIFY(A) STRINGIFY_(A)

  #if LIBFUZZER_MSVC
    // Copied from compiler-rt/lib/sanitizer_common/sanitizer_win_defs.h
    #if defined(_M_IX86) || defined(__i386__)
      #define WIN_SYM_PREFIX "_"
    #else
      #define WIN_SYM_PREFIX
    #endif

    // Declare external functions as having alternativenames, so that we can
    // determine if they are not defined.
    #define EXTERNAL_FUNC(Name, Default)                              \
      __pragma(                                                       \
          comment(linker, "/alternatename:" WIN_SYM_PREFIX STRINGIFY( \
                              Name) "=" WIN_SYM_PREFIX STRINGIFY(Default)))
  #else
    // Declare external functions as weak to allow them to default to a
    // specified function if not defined explicitly. We must use weak symbols
    // because clang's support for alternatename is not 100%, see
    // https://bugs.llvm.org/show_bug.cgi?id=40218 for more details.
    #define EXTERNAL_FUNC(Name, Default) \
      __attribute__((weak, alias(STRINGIFY(Default))))
  #endif  // LIBFUZZER_MSVC

extern "C" {

  #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN)         \
    RETURN_TYPE NAME##Def FUNC_SIG {                          \
                                                              \
      Printf("ERROR: Function \"%s\" not defined.\n", #NAME); \
      exit(1);                                                \
                                                              \
    }                                                         \
    EXTERNAL_FUNC(NAME, NAME##Def) RETURN_TYPE NAME FUNC_SIG

  #include "FuzzerExtFunctions.def"

  #undef EXT_FUNC

}

template <typename T>
static T *GetFnPtr(T *Fun, T *FunDef, const char *FnName, bool WarnIfMissing) {

  if (Fun == FunDef) {

    if (WarnIfMissing)
      Printf("WARNING: Failed to find function \"%s\".\n", FnName);
    return nullptr;

  }

  return Fun;

}

namespace fuzzer {

ExternalFunctions::ExternalFunctions() {

  #define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
    this->NAME = GetFnPtr<decltype(::NAME)>(::NAME, ::NAME##Def, #NAME, WARN);

  #include "FuzzerExtFunctions.def"

  #undef EXT_FUNC

}

}  // namespace fuzzer

#endif  // LIBFUZZER_WINDOWS

