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// 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
//
//
// 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 "absl/base/internal/raw_logging.h"
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#ifdef __EMSCRIPTEN__
#include <emscripten/console.h>
#endif
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/internal/atomic_hook.h"
#include "absl/base/internal/errno_saver.h"
#include "absl/base/log_severity.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(__FreeBSD__) || \
defined(__Fuchsia__) || defined(__native_client__) || \
defined(__OpenBSD__) || defined(__EMSCRIPTEN__) || defined(__ASYLO__)
#include <unistd.h>
#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(__FreeBSD__)) && !defined(__ANDROID__)
#include <sys/syscall.h>
#define ABSL_HAVE_SYSCALL_WRITE 1
#define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
#else
#undef ABSL_HAVE_SYSCALL_WRITE
#endif
#ifdef _WIN32
#include <io.h>
#define ABSL_HAVE_RAW_IO 1
#define ABSL_LOW_LEVEL_WRITE_SUPPORTED 1
#else
#undef ABSL_HAVE_RAW_IO
#endif
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace raw_log_internal {
namespace {
// 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 selected set of platforms for which we expect not to be able to raw log.
#ifdef ABSL_LOW_LEVEL_WRITE_SUPPORTED
constexpr 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[].
bool VADoRawLog(char** buf, int* size, const char* format, va_list ap)
ABSL_PRINTF_ATTRIBUTE(3, 0);
bool VADoRawLog(char** buf, int* size, const char* format, va_list ap) {
if (*size < 0) return false;
int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
bool result = true;
if (n < 0 || n > *size) {
result = false;
if (static_cast<size_t>(*size) > sizeof(kTruncated)) {
n = *size - static_cast<int>(sizeof(kTruncated));
} else {
n = 0; // no room for truncation message
}
}
*size -= n;
*buf += n;
return result;
}
#endif // ABSL_LOW_LEVEL_WRITE_SUPPORTED
constexpr int kLogBufSize = 3000;
// CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
// that invoke malloc() and getenv() that might acquire some locks.
// 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, ...) {
if (*size < 0) return false;
va_list ap;
va_start(ap, format);
int n = vsnprintf(*buf, static_cast<size_t>(*size), format, ap);
va_end(ap);
if (n < 0 || n > *size) return false;
*size -= n;
*buf += n;
return true;
}
bool DefaultLogFilterAndPrefix(absl::LogSeverity, const char* file, int line,
char** buf, int* buf_size) {
DoRawLog(buf, buf_size, "[%s : %d] RAW: ", file, line);
return true;
}
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
absl::base_internal::AtomicHook<LogFilterAndPrefixHook>
log_filter_and_prefix_hook(DefaultLogFilterAndPrefix);
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES
absl::base_internal::AtomicHook<AbortHook> abort_hook;
void RawLogVA(absl::LogSeverity severity, const char* file, int line,
const char* format, va_list ap) ABSL_PRINTF_ATTRIBUTE(4, 0);
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 (severity < static_cast<absl::LogSeverity>(ABSL_MIN_LOG_LEVEL) &&
severity < absl::LogSeverity::kFatal) {
enabled = false;
}
#endif
enabled = log_filter_and_prefix_hook(severity, file, line, &buf, &size);
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);
}
AsyncSignalSafeWriteError(buffer, strlen(buffer));
}
#else
static_cast<void>(format);
static_cast<void>(ap);
static_cast<void>(enabled);
#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();
}
}
// Non-formatting version of RawLog().
//
// TODO(gfalcon): When string_view no longer depends on base, change this
// interface to take its message as a string_view instead.
void DefaultInternalLog(absl::LogSeverity severity, const char* file, int line,
const std::string& message) {
RawLog(severity, file, line, "%.*s", static_cast<int>(message.size()),
message.data());
}
} // namespace
void AsyncSignalSafeWriteError(const char* s, size_t len) {
if (!len) return;
absl::base_internal::ErrnoSaver errno_saver;
#if defined(__EMSCRIPTEN__)
// In WebAssembly, bypass filesystem emulation via fwrite.
if (s[len - 1] == '\n') {
// Skip a trailing newline character as emscripten_errn adds one itself.
len--;
}
// emscripten_errn was introduced in 3.1.41 but broken in standalone mode
// until 3.1.43.
#if ABSL_INTERNAL_EMSCRIPTEN_VERSION >= 3001043
emscripten_errn(s, len);
#else
char buf[kLogBufSize];
if (len >= kLogBufSize) {
len = kLogBufSize - 1;
constexpr size_t trunc_len = sizeof(kTruncated) - 2;
memcpy(buf + len - trunc_len, kTruncated, trunc_len);
buf[len] = '\0';
len -= trunc_len;
} else {
buf[len] = '\0';
}
memcpy(buf, s, len);
_emscripten_err(buf);
#endif
#elif defined(ABSL_HAVE_SYSCALL_WRITE)
// We prefer calling write via `syscall` to minimize the risk of libc doing
// something "helpful".
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, static_cast<unsigned>(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
}
ABSL_INTERNAL_ATOMIC_HOOK_ATTRIBUTES ABSL_DLL
absl::base_internal::AtomicHook<InternalLogFunction>
internal_log_function(DefaultInternalLog);
void RegisterLogFilterAndPrefixHook(LogFilterAndPrefixHook func) {
log_filter_and_prefix_hook.Store(func);
}
void RegisterAbortHook(AbortHook func) { abort_hook.Store(func); }
void RegisterInternalLogFunction(InternalLogFunction func) {
internal_log_function.Store(func);
}
} // namespace raw_log_internal
ABSL_NAMESPACE_END
} // namespace absl