@node strerror_r
@subsection @code{strerror_r}
@findex strerror_r

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/strerror_r.html}

LSB specification:
@itemize
@item
@url{https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/baselib-strerror-r.html}
@item
@url{https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/baselib---xpg-strerror-r.html}
@end itemize

Gnulib module: strerror_r-posix
@mindex strerror_r-posix

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
NetBSD 3.0, Minix 3.1.8, HP-UX 11.23, Solaris 9, mingw, MSVC 14.
@item
glibc, Cygwin, Android, and AIX+@code{_LINUX_SOURCE_COMPAT}
have an incompatible version of this function.
The POSIX compliant code
@smallexample
char *s = (strerror_r (err, buf, buflen) == 0 ? buf : NULL);
@end smallexample
is essentially equivalent to this code using the glibc function:
@smallexample
char *s = strerror_r (err, buf, buflen);
@end smallexample
@item
This function clobbers the @code{strerror} buffer on some platforms:
Cygwin 1.7.9.
@item
This function is sometimes not declared in @code{<string.h>} on some platforms:
glibc 2.8.
@item
The third argument is of type @code{int} instead of @code{size_t} on some
platforms:
AIX 5.1.
@item
When this function fails, it returns @minus{}1 and sets @code{errno}, instead of
returning the error number, on some platforms:
glibc 2.12 with @code{-D_POSIX_C_SOURCE=200112L}, AIX 6.1.
@item
When this function fails, it corrupts @code{errno}, on some platforms:
Solaris 10.
@item
This function does not support many error values defined in @code{<errno.h>} on
some platforms:
MSVC 14.
@item
This function does not support the error values that are specified by POSIX
but not defined by the system, on some platforms:
OpenBSD 4.0, NonStop Kernel, Cygwin 1.5.x.
@item
This function reports failure for @code{strerror_r(0, buf, len)},
although POSIX requires this to succeed, on some platforms:
FreeBSD 8.2.
@item
This function produces a different string for @code{0} than
@code{strerror} on some platforms:
macOS 14.
@item
This function always fails when the third argument is less than 80 on some
platforms:
HP-UX 11.31.
@item
When the buffer is too small and the value is in range, this function
does not fail, but instead truncates the result and returns 0 on some
platforms:
AIX 6.1, Haiku 2017.
@item
When the value is not in range or the buffer is too small, this
function fails to leave a NUL-terminated string in the buffer on some
platforms:
glibc 2.13, FreeBSD 8.2, Solaris 10.
@item
When the value is out of range but the buffer is too small, this
function does not always return the longest possible string on some
platforms:
OpenBSD 4.7.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@end itemize

@mindex xstrerror
Note: Gnulib has a module @code{xstrerror}, with the property that
@code{xstrerror (NULL, errnum)} returns the value of @code{strerror_r}
as a freshly allocated string.
(Recall that the expression @code{strerror (errnum)} is not multithread-safe.)
