Handle both the XSI and GNU versions of strerror_r

Trying to force the XSI version by undefining _GNU_SOURCE can lead
to compilation errors on some systems because of headers expecting
that _GNU_SOURCE is defined.

This commit uses define checks to detect which version we have.
I tried making an overloaded function (int and const char*) instead,
but that led to a warning about one of the variants being unused.
This commit is contained in:
JosJuice 2017-12-16 13:08:50 +01:00
parent ba01642dc7
commit bd5da5cfd6

View File

@ -2,21 +2,10 @@
// Licensed under GPLv2+
// Refer to the license.txt file included.
// The code in GetErrorMessage can't handle some systems having the
// GNU version of strerror_r and other systems having the XSI version,
// so we undefine _GNU_SOURCE here in an attempt to always get the XSI version.
// We include cstring before all other headers in case cstring is included
// indirectly (without undefining _GNU_SOURCE) by some other header.
#ifdef _GNU_SOURCE
#undef _GNU_SOURCE
#include <cstring>
#define _GNU_SOURCE
#else
#include <cstring>
#endif
#include <cstddef>
#include <cstring>
#include <errno.h>
#include <type_traits>
#include "Common/CommonFuncs.h"
@ -33,13 +22,20 @@ std::string LastStrerrorString()
{
char error_message[BUFFER_SIZE];
// We assume that the XSI-compliant version of strerror_r (returns int) is used
// rather than the GNU version (returns char*). The returned value is stored to
// an int variable to get a compile-time check that the return type is not char*.
const int result = strerror_r(errno, error_message, BUFFER_SIZE);
if (result != 0)
return "";
return std::string(error_message);
// There are two variants of strerror_r. The XSI version stores the message to the passed-in
// buffer and returns an int (0 on success). The GNU version returns a pointer to the message,
// which might have been stored in the passed-in buffer or might be a static string.
// We check defines in order to figure out variant is in use, and we store the returned value
// to a variable so that we'll get a compile-time check that our assumption was correct.
#if defined(__GLIBC__) && (_GNU_SOURCE || (_POSIX_C_SOURCE < 200112L && _XOPEN_SOURCE < 600))
const char* str = strerror_r(errno, error_message, BUFFER_SIZE);
return std::string(str);
#else
int error_code = strerror_r(errno, error_message, BUFFER_SIZE);
return error_code == 0 ? std::string(error_message) : "";
#endif
}
#ifdef _WIN32