SafeAssert: async-signal-safe CHECK, DCHECK

Summary: To be used from the (new) fatal signal handler.

Test Plan: test added

Reviewed By: lucian@fb.com

FB internal diff: D1076168

@override-unit-failures

folly/SafeAssert.cpp

+/*
+ * Copyright 2013 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "folly/SafeAssert.h"
+
+#include "folly/Conv.h"
+#include "folly/FileUtil.h"
+
+namespace folly { namespace detail {
+
+namespace {
+void writeStderr(const char* s) {
+  writeFull(STDERR_FILENO, s, strlen(s));
+}
+}  // namespace
+
+void assertionFailure(const char* expr, const char* msg, const char* file,
+                      unsigned int line, const char* function) {
+  writeStderr("\n\nAssertion failure: ");
+  writeStderr(expr);
+  writeStderr("\nMessage: ");
+  writeStderr(msg);
+  writeStderr("\nFile: ");
+  writeStderr(file);
+  writeStderr("\nLine: ");
+  char buf[20];
+  uint32_t n = uint64ToBufferUnsafe(line, buf);
+  writeFull(STDERR_FILENO, buf, n);
+  writeStderr("\nFunction: ");
+  writeStderr(function);
+  writeStderr("\n");
+  fsyncNoInt(STDERR_FILENO);
+  abort();
+}
+
+}}  // namespaces
+

folly/SafeAssert.h

+/*
+ * Copyright 2013 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FOLLY_SAFEASSERT_H_
+#define FOLLY_SAFEASSERT_H_
+
+#include "folly/Portability.h"
+#include "folly/Preprocessor.h"
+
+/**
+ * Verify that the expression is true. If not, prints an error message
+ * (containing msg) to stderr and abort()s. Just like CHECK(), but only
+ * logs to stderr and only does async-signal-safe calls.
+ */
+#define FOLLY_SAFE_CHECK(expr, msg) \
+  ((expr) ? static_cast<void>(0) : \
+   ::folly::detail::assertionFailure( \
+       FB_STRINGIZE(expr), (msg), __FILE__, __LINE__, __PRETTY_FUNCTION__))
+
+/**
+ * In debug mode, verify that the expression is true. Otherwise, do nothing
+ * (do not even evaluate expr). Just like assert() or DCHECK(), but only
+ * logs to stderr and only does async-signal-safe calls.
+ */
+#ifdef NDEBUG
+#define FOLLY_SAFE_DCHECK(expr, msg) (static_cast<void>(0))
+#else
+#define FOLLY_SAFE_DCHECK FOLLY_SAFE_CHECK
+#endif
+
+namespace folly { namespace detail {
+
+void assertionFailure(const char* expr, const char* msg, const char* file,
+                      unsigned int line, const char* function)
+  FOLLY_NORETURN;
+
+}}  // namespace folly
+
+#endif /* FOLLY_SAFEASSERT_H_ */
+

folly/test/SafeAssertTest.cpp

+/*
+ * Copyright 2013 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "folly/SafeAssert.h"
+
+#include <glog/logging.h>
+#include <gtest/gtest.h>
+
+#include "folly/Benchmark.h"
+
+using namespace folly;
+
+void fail() {
+  FOLLY_SAFE_CHECK(0, "hello");
+}
+
+void succeed() {
+  FOLLY_SAFE_CHECK(1, "world");
+}
+
+TEST(SafeAssert, AssertionFailure) {
+  succeed();
+  EXPECT_DEATH(fail(), ".*Assertion failure:.*hello.*");
+}
+