| // 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. |
| |
| #include "build/build_config.h" |
| #include "base/safe_strerror_posix.h" |
| |
| #include <errno.h> |
| #include <stdio.h> |
| #include <string.h> |
| |
| #if (defined(__GLIBC__) || defined(OS_NACL)) |
| #define USE_HISTORICAL_STRERRO_R 1 |
| #else |
| #define USE_HISTORICAL_STRERRO_R 0 |
| #endif |
| |
| #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. |
| #if defined(__LB_XB1__) || defined(__LB_XB360__) || defined(__STDC_LIB_EXT1__) |
| strerror_s(buf, len, err); |
| #else |
| wrap_posix_strerror_r(&strerror_r, err, buf, len); |
| #endif |
| } |
| |
| 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); |
| } |