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/** @file
* @brief Convert errno value to std::string, thread-safely if possible
*/
/* Copyright (C) 2014,2015,2016,2021 Olly Betts
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <config.h>
#include "errno_to_string.h"
// On Linux, sys_errlist and sys_nerr need <stdio.h>, though the man page
// says <errno.h>. The man page seems to match other platforms such as
// NetBSD, so include both headers to ensure we get them.
#include <errno.h>
// <cstring> doesn't give us strerror_r() with Sun C++ 5.9.
#include <string.h>
#if defined HAVE__SYS_ERRLIST_AND__SYS_NERR || \
defined HAVE_SYS_ERRLIST_AND_SYS_NERR
# include <stdio.h>
// With mingw and MSVC they're provided by <stdlib.h>.
# include <stdlib.h>
#endif
#include "str.h"
using namespace std;
void
errno_to_string(int e, string& s)
{
// Use a thread-safe way to convert an errno value to a string if possible.
#ifdef HAVE_STRERRORDESC_NP
// GNU-specific replacement for sys_errlist and sys_nerr, added in glibc
// 2.32.
const char* desc = strerrordesc_np(e);
if (desc) {
s += desc;
} else {
s += "Unknown error ";
s += str(e);
}
#elif defined HAVE__SYS_ERRLIST_AND__SYS_NERR
// Old-style Unix fixed array of strings.
if (e >= 0 && e < _sys_nerr && _sys_errlist[e]) {
s += _sys_errlist[e];
} else {
s += "Unknown error ";
s += str(e);
}
#elif defined HAVE_SYS_ERRLIST_AND_SYS_NERR
// Old-style Unix fixed array of strings.
if (e >= 0 && e < sys_nerr && sys_errlist[e]) {
s += sys_errlist[e];
} else {
s += "Unknown error ";
s += str(e);
}
#elif HAVE_DECL_STRERROR_R
// POSIX specifies strerror_r() to provide a thread-safe way to translate
// an errno value to a string.
//
// Unhelpfully this requires us to pass in a buffer, but we don't know how
// big to make it to reliably be able to convert all possible errno values,
// and the implementation is permitted to return localised strings so the
// maximum possible length may vary depending on the current locale
// settings.
//
// If the buffer passed is too small, then with older glibc errno gets
// stomped on, so growing the buffer on error and retrying isn't a great
// answer. Hence we only use strerror_r() if we don't have a better
// alternative.
//
// Another reason to have support for alternative approaches is that
// strerror_r() is marked as "optional" by POSIX.
//
// A further complication is there's a GNU-specific strerror_r() with a
// different return value type.
//
// The strerror_r(3) man page on Linux suggests a buffer size of 1024
// characters, noting that glibc uses this size for strerror(). The
// actual longest on Linux in English is EILSEQ which needs 50 bytes.
char buf[1024];
# ifdef STRERROR_R_CHAR_P
// Returns char* pointing to string describing error.
s += strerror_r(e, buf, sizeof(buf));
# else
// XSI-compliant strerror_r returns int: 0 means success; a positive error
// number should be returned on error, but glibc < 2.13 returns -1 and sets
// errno.
int r = strerror_r(e, buf, sizeof(buf));
if (r == 0) {
s += buf;
} else {
s += "Unknown error ";
s += str(e);
}
# endif
#else
// Not thread safe.
//
// We can assume the return value is non-NULL because "C99 and POSIX.1-2008
// require the return value to be non-NULL" and we require C++11 which
// incorporates C99.
s += strerror(e);
#endif
}
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