Update from https://crrev.com/333737

base/safe_strerror_posix.cc

-// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#if defined(__ANDROID__)
-// Post-L versions of bionic define the GNU-specific strerror_r if _GNU_SOURCE
-// is defined, but the symbol is renamed to __gnu_strerror_r which only exists
-// on those later versions. To preserve ABI compatibility with older versions,
-// undefine _GNU_SOURCE and use the POSIX version.
-#undef _GNU_SOURCE
-#endif
-
-#include "build/build_config.h"
-#include "base/safe_strerror_posix.h"
-
-#include <errno.h>
-#include <stdio.h>
-#include <string.h>
-
-#define USE_HISTORICAL_STRERRO_R (defined(__GLIBC__) || defined(OS_NACL))
-
-#if USE_HISTORICAL_STRERRO_R && defined(__GNUC__)
-// GCC will complain about the unused second wrap function unless we tell it
-// that we meant for them to be potentially unused, which is exactly what this
-// attribute is for.
-#define POSSIBLY_UNUSED __attribute__((unused))
-#else
-#define POSSIBLY_UNUSED
-#endif
-
-#if USE_HISTORICAL_STRERRO_R
-// glibc has two strerror_r functions: a historical GNU-specific one that
-// returns type char *, and a POSIX.1-2001 compliant one available since 2.3.4
-// that returns int. This wraps the GNU-specific one.
-static void POSSIBLY_UNUSED wrap_posix_strerror_r(
-    char *(*strerror_r_ptr)(int, char *, size_t),
-    int err,
-    char *buf,
-    size_t len) {
-  // GNU version.
-  char *rc = (*strerror_r_ptr)(err, buf, len);
-  if (rc != buf) {
-    // glibc did not use buf and returned a static string instead. Copy it
-    // into buf.
-    buf[0] = '\0';
-    strncat(buf, rc, len - 1);
-  }
-  // The GNU version never fails. Unknown errors get an "unknown error" message.
-  // The result is always null terminated.
-}
-#endif  // USE_HISTORICAL_STRERRO_R
-
-// Wrapper for strerror_r functions that implement the POSIX interface. POSIX
-// does not define the behaviour for some of the edge cases, so we wrap it to
-// guarantee that they are handled. This is compiled on all POSIX platforms, but
-// it will only be used on Linux if the POSIX strerror_r implementation is
-// being used (see below).
-static void POSSIBLY_UNUSED wrap_posix_strerror_r(
-    int (*strerror_r_ptr)(int, char *, size_t),
-    int err,
-    char *buf,
-    size_t len) {
-  int old_errno = errno;
-  // Have to cast since otherwise we get an error if this is the GNU version
-  // (but in such a scenario this function is never called). Sadly we can't use
-  // C++-style casts because the appropriate one is reinterpret_cast but it's
-  // considered illegal to reinterpret_cast a type to itself, so we get an
-  // error in the opposite case.
-  int result = (*strerror_r_ptr)(err, buf, len);
-  if (result == 0) {
-    // POSIX is vague about whether the string will be terminated, although
-    // it indirectly implies that typically ERANGE will be returned, instead
-    // of truncating the string. We play it safe by always terminating the
-    // string explicitly.
-    buf[len - 1] = '\0';
-  } else {
-    // Error. POSIX is vague about whether the return value is itself a system
-    // error code or something else. On Linux currently it is -1 and errno is
-    // set. On BSD-derived systems it is a system error and errno is unchanged.
-    // We try and detect which case it is so as to put as much useful info as
-    // we can into our message.
-    int strerror_error;  // The error encountered in strerror
-    int new_errno = errno;
-    if (new_errno != old_errno) {
-      // errno was changed, so probably the return value is just -1 or something
-      // else that doesn't provide any info, and errno is the error.
-      strerror_error = new_errno;
-    } else {
-      // Either the error from strerror_r was the same as the previous value, or
-      // errno wasn't used. Assume the latter.
-      strerror_error = result;
-    }
-    // snprintf truncates and always null-terminates.
-    snprintf(buf,
-             len,
-             "Error %d while retrieving error %d",
-             strerror_error,
-             err);
-  }
-  errno = old_errno;
-}
-
-void safe_strerror_r(int err, char *buf, size_t len) {
-  if (buf == NULL || len <= 0) {
-    return;
-  }
-  // If using glibc (i.e., Linux), the compiler will automatically select the
-  // appropriate overloaded function based on the function type of strerror_r.
-  // The other one will be elided from the translation unit since both are
-  // static.
-  wrap_posix_strerror_r(&strerror_r, err, buf, len);
-}
-
-std::string safe_strerror(int err) {
-  const int buffer_size = 256;
-  char buf[buffer_size];
-  safe_strerror_r(err, buf, sizeof(buf));
-  return std::string(buf);
-}