1//===- FuzzerExtFunctionsWeak.cpp - Interface to external functions -------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8// Implementation for Linux. This relies on the linker's support for weak
9// symbols. We don't use this approach on Apple platforms because it requires
10// clients of LibFuzzer to pass ``-U _<symbol_name>`` to the linker to allow
11// weak symbols to be undefined. That is a complication we don't want to expose
12// to clients right now.
13//===----------------------------------------------------------------------===//
14#include "FuzzerPlatform.h"
15#if LIBFUZZER_LINUX || LIBFUZZER_NETBSD || LIBFUZZER_FUCHSIA || \
16 LIBFUZZER_FREEBSD || LIBFUZZER_EMSCRIPTEN
17
18#include "FuzzerExtFunctions.h"
19#include "FuzzerIO.h"
20
21extern "C" {
22// Declare these symbols as weak to allow them to be optionally defined.
23#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
24 __attribute__((weak, visibility("default"))) RETURN_TYPE NAME FUNC_SIG
25
26#include "FuzzerExtFunctions.def"
27
28#undef EXT_FUNC
29}
30
31using namespace fuzzer;
32
33static void CheckFnPtr(void *FnPtr, const char *FnName, bool WarnIfMissing) {
34 if (FnPtr == nullptr && WarnIfMissing) {
35 Printf("WARNING: Failed to find function \"%s\".\n", FnName);
36 }
37}
38
39namespace fuzzer {
40
41ExternalFunctions::ExternalFunctions() {
42#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
43 this->NAME = ::NAME; \
44 CheckFnPtr(reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(::NAME)), \
45 #NAME, WARN);
46
47#include "FuzzerExtFunctions.def"
48
49#undef EXT_FUNC
50}
51
52} // namespace fuzzer
53
54#endif
55