llvm/lib/Fuzzer/FuzzerIO.h
Marcos Pividori ed3dca071a [libFuzzer] Avoid undefined behavior, properly discard output to stdout/stderr.
Fix libFuzzer when setting -close_fd_mask to a non-zero value.
In previous implementation, libFuzzer closes the file descriptors for
stdout/stderr. This has some disavantages:

For `fuzzer-fdmask.test`, we write directly to stdout and stderr using the
file streams stdout and stderr, after the file descriptors are closed, which is
undefined behavior. In Windows, in particular, this was making the test fail.

Also, if we close stdout and we open a new file in libFuzzer, we get the file
descriptor 1, which could generate problem if some code assumes file descriptors
refers to stdout and works directly writing to the file descriptor 1, but it
will be writing to the opened file (for example using std::cout).

Instead of closing the file descriptors, I redirect the output to /dev/null on
linux and nul on Windows.

Differential Revision: https://reviews.llvm.org/D28718

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292743 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-22 01:58:45 +00:00

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1.9 KiB
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//===- FuzzerIO.h - Internal header for IO utils ----------------*- C++ -* ===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// IO interface.
//===----------------------------------------------------------------------===//
#ifndef LLVM_FUZZER_IO_H
#define LLVM_FUZZER_IO_H
#include "FuzzerDefs.h"
namespace fuzzer {
long GetEpoch(const std::string &Path);
Unit FileToVector(const std::string &Path, size_t MaxSize = 0,
bool ExitOnError = true);
std::string FileToString(const std::string &Path);
void CopyFileToErr(const std::string &Path);
void WriteToFile(const Unit &U, const std::string &Path);
void ReadDirToVectorOfUnits(const char *Path, std::vector<Unit> *V,
long *Epoch, size_t MaxSize, bool ExitOnError);
// Returns "Dir/FileName" or equivalent for the current OS.
std::string DirPlusFile(const std::string &DirPath,
const std::string &FileName);
// Returns the name of the dir, similar to the 'dirname' utility.
std::string DirName(const std::string &FileName);
// Returns path to a TmpDir.
std::string TmpDir();
bool IsInterestingCoverageFile(const std::string &FileName);
void DupAndCloseStderr();
void CloseStdout();
void Printf(const char *Fmt, ...);
// Platform specific functions:
bool IsFile(const std::string &Path);
void ListFilesInDirRecursive(const std::string &Dir, long *Epoch,
std::vector<std::string> *V, bool TopDir);
char GetSeparator();
FILE* OpenFile(int Fd, const char *Mode);
int CloseFile(int Fd);
int DuplicateFile(int Fd);
void RemoveFile(const std::string &Path);
void DiscardOutput(int Fd);
} // namespace fuzzer
#endif // LLVM_FUZZER_IO_H