Add fuzzer for Rust demangler

[dblaikie]

Looks good, thanks!

llvm/tools/llvm-rust-demangle-fuzzer/llvm-rust-demangle-fuzzer.cpp

17–19

Since free(nullptr) is a no-op, you could skip the 'if' here if you like.

[tmiasko]

Remove unnecessary nullptr check before free.

[tmiasko]

Could you commit this for me? Thank you.

Tomasz Miąsko <[e-mail]>

llvm/tools/llvm-rust-demangle-fuzzer/CMakeLists.txt

+set(LLVM_LINK_COMPONENTS
+  Demangle
+  FuzzMutate
+  Support
+)
+
+add_llvm_fuzzer(llvm-rust-demangle-fuzzer
+  llvm-rust-demangle-fuzzer.cpp
+  DUMMY_MAIN DummyDemanglerFuzzer.cpp
+  )

llvm/tools/llvm-rust-demangle-fuzzer/DummyDemanglerFuzzer.cpp

+//===-- DummyDemanglerFuzzer.cpp - Entry point to sanity check the fuzzer -===//
+//
+// 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 main so we can build and test without linking libFuzzer.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/FuzzMutate/FuzzerCLI.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
+int main(int argc, char *argv[]) {
+  return llvm::runFuzzerOnInputs(argc, argv, LLVMFuzzerTestOneInput);
+}

llvm/tools/llvm-rust-demangle-fuzzer/llvm-rust-demangle-fuzzer.cpp

+//===--- llvm-demangle-fuzzer.cpp - Fuzzer for the Rust Demangler ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Demangle/Demangle.h"
+
+#include <cstdint>
+#include <cstdlib>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  std::string NullTerminatedString((const char *)Data, Size);
+  int Status = 0;
+  if (char *Demangled = llvm::rustDemangle(NullTerminatedString.c_str(),
+                                           nullptr, nullptr, &Status))
+    std::free(Demangled);
+  return 0;
+}