From c2e754829628d1e9b7a16b3389cfdace76950fdf Mon Sep 17 00:00:00 2001 From: misterg Date: Tue, 19 Sep 2017 16:54:40 -0400 Subject: Initial Commit --- absl/base/internal/raw_logging.cc | 225 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 225 insertions(+) create mode 100644 absl/base/internal/raw_logging.cc (limited to 'absl/base/internal/raw_logging.cc') diff --git a/absl/base/internal/raw_logging.cc b/absl/base/internal/raw_logging.cc new file mode 100644 index 000000000000..d197d444a6f4 --- /dev/null +++ b/absl/base/internal/raw_logging.cc @@ -0,0 +1,225 @@ +// Copyright 2017 The Abseil Authors. +// +// 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 +#include +#include +#include +#include +#include + +#include "absl/base/config.h" +#include "absl/base/internal/atomic_hook.h" +#include "absl/base/internal/log_severity.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/base/port.h" + +// We know how to perform low-level writes to stderr in POSIX and Windows. For +// these platforms, we define the token ABSL_LOW_LEVEL_WRITE_SUPPORTED. +// Much of raw_logging.cc becomes a no-op when we can't output messages, +// although a FATAL ABSL_RAW_LOG message will still abort the process. + +// ABSL_HAVE_POSIX_WRITE is defined when the platform provides posix write() +// (as from unistd.h) +// +// This preprocessor token is also defined in raw_io.cc. If you need to copy +// this, consider moving both to config.h instead. +#if defined(__linux__) || defined(__APPLE__) || defined(__Fuchsia__) || \ + defined(__GENCLAVE__) +#include +#define ABSL_HAVE_POSIX_WRITE 1 +#define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1 +#else +#undef ABSL_HAVE_POSIX_WRITE +#endif + +// ABSL_HAVE_SYSCALL_WRITE is defined when the platform provides the syscall +// syscall(SYS_write, /*int*/ fd, /*char* */ buf, /*size_t*/ len); +// for low level operations that want to avoid libc. +#if defined(__linux__) && !defined(__ANDROID__) +#include +#define ABSL_HAVE_SYSCALL_WRITE 1 +#define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1 +#else +#undef ABSL_HAVE_SYSCALL_WRITE +#endif + +#ifdef _WIN32 +#include +#define ABSL_HAVE_RAW_IO 1 +#define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1 +#else +#undef ABSL_HAVE_RAW_IO +#endif + +// TODO(gfalcon): We want raw-logging to work on as many platforms as possible. +// Explicitly #error out when not ABSL_LOW_LEVEL_WRITE_SUPPORTED, except for a +// whitelisted set of platforms for which we expect not to be able to raw log. + +ABSL_CONST_INIT static absl::base_internal::AtomicHook< + absl::raw_logging_internal::LogPrefixHook> log_prefix_hook; +ABSL_CONST_INIT static absl::base_internal::AtomicHook< + absl::raw_logging_internal::AbortHook> abort_hook; + +#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED +static const char kTruncated[] = " ... (message truncated)\n"; + +// sprintf the format to the buffer, adjusting *buf and *size to reflect the +// consumed bytes, and return whether the message fit without truncation. If +// truncation occurred, if possible leave room in the buffer for the message +// kTruncated[]. +inline static bool VADoRawLog(char** buf, int* size, + const char* format, va_list ap) { + int n = vsnprintf(*buf, *size, format, ap); + bool result = true; + if (n < 0 || n > *size) { + result = false; + if (static_cast(*size) > sizeof(kTruncated)) { + n = *size - sizeof(kTruncated); // room for truncation message + } else { + n = 0; // no room for truncation message + } + } + *size -= n; + *buf += n; + return result; +} +#endif // ABSL_LOW_LEVEL_WRITE_SUPPORTED + +static constexpr int kLogBufSize = 3000; + +namespace absl { +namespace raw_logging_internal { +void SafeWriteToStderr(const char *s, size_t len); +} // namespace raw_logging_internal +} // namespace absl + +namespace { + +// CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths +// that invoke malloc() and getenv() that might acquire some locks. +// If this becomes a problem we should reimplement a subset of vsnprintf +// that does not need locks and malloc. +// E.g. google3/third_party/clearsilver/core/util/snprintf.c +// looks like such a reimplementation. + +// Helper for RawLog below. +// *DoRawLog writes to *buf of *size and move them past the written portion. +// It returns true iff there was no overflow or error. +bool DoRawLog(char** buf, int* size, const char* format, ...) + ABSL_PRINTF_ATTRIBUTE(3, 4); +bool DoRawLog(char** buf, int* size, const char* format, ...) { + va_list ap; + va_start(ap, format); + int n = vsnprintf(*buf, *size, format, ap); + va_end(ap); + if (n < 0 || n > *size) return false; + *size -= n; + *buf += n; + return true; +} + +void RawLogVA(absl::LogSeverity severity, const char* file, int line, + const char* format, va_list ap) { + char buffer[kLogBufSize]; + char* buf = buffer; + int size = sizeof(buffer); +#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED + bool enabled = true; +#else + bool enabled = false; +#endif + +#ifdef ABSL_MIN_LOG_LEVEL + if (static_cast(severity) < ABSL_MIN_LOG_LEVEL && + severity < absl::LogSeverity::kFatal) { + enabled = false; + } +#endif + + auto log_prefix_hook_ptr = log_prefix_hook.Load(); + if (log_prefix_hook_ptr) { + enabled = log_prefix_hook_ptr(severity, file, line, &buf, &size); + } else { + if (enabled) { + DoRawLog(&buf, &size, "[%s : %d] RAW: ", file, line); + } + } + const char* const prefix_end = buf; + +#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED + if (enabled) { + bool no_chop = VADoRawLog(&buf, &size, format, ap); + if (no_chop) { + DoRawLog(&buf, &size, "\n"); + } else { + DoRawLog(&buf, &size, "%s", kTruncated); + } + absl::raw_logging_internal::SafeWriteToStderr(buffer, strlen(buffer)); + } +#else + static_cast(format); + static_cast(ap); +#endif + + // Abort the process after logging a FATAL message, even if the output itself + // was suppressed. + if (severity == absl::LogSeverity::kFatal) { + abort_hook(file, line, buffer, prefix_end, buffer + kLogBufSize); + abort(); + } +} + +} // namespace + +namespace absl { +namespace raw_logging_internal { + +// Writes the provided buffer directly to stderr, in a safe, low-level manner. +// +// In POSIX this means calling write(), which is async-signal safe and does +// not malloc. If the platform supports the SYS_write syscall, we invoke that +// directly to side-step any libc interception. +void SafeWriteToStderr(const char *s, size_t len) { +#if defined(ABSL_HAVE_SYSCALL_WRITE) + syscall(SYS_write, STDERR_FILENO, s, len); +#elif defined(ABSL_HAVE_POSIX_WRITE) + write(STDERR_FILENO, s, len); +#elif defined(ABSL_HAVE_RAW_IO) + _write(/* stderr */ 2, s, len); +#else + // stderr logging unsupported on this platform + (void) s; + (void) len; +#endif +} + +void RawLog(absl::LogSeverity severity, const char* file, int line, + const char* format, ...) { + va_list ap; + va_start(ap, format); + RawLogVA(severity, file, line, format, ap); + va_end(ap); +} + +bool RawLoggingFullySupported() { +#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED + return true; +#else // !ABSL_LOW_LEVEL_WRITE_SUPPORTED + return false; +#endif // !ABSL_LOW_LEVEL_WRITE_SUPPORTED +} + +} // namespace raw_logging_internal +} // namespace absl -- cgit 1.4.1