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10.1076 strerror_r

POSIX specification:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/strerror_r.html

LSB specification:

• https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/baselib-strerror-r.html
• https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/baselib---xpg-strerror-r.html

Gnulib module: strerror_r-posix

Portability problems fixed by Gnulib:

• This function is missing on some platforms: NetBSD 3.0, Minix 3.1.8, HP-UX 11.23, IRIX 6.5, Solaris 9, mingw, MSVC 14.
• glibc, Cygwin, and Android have an incompatible version of this function. The POSIX compliant code

  char *s = (strerror_r (err, buf, buflen) == 0 ? buf : NULL);
  

  is essentially equivalent to this code using the glibc function:

  char *s = strerror_r (err, buf, buflen);
  

• This function clobbers the strerror buffer on some platforms: Cygwin 1.7.9.
• This function is sometimes not declared in <string.h> on some platforms: glibc 2.8.
• The third argument is of type int instead of size_t on some platforms: AIX 5.1.
• When this function fails, it returns -1 and sets errno, instead of returning the error number, on some platforms: glibc 2.12 with -D_POSIX_C_SOURCE=200112L, AIX 6.1.
• When this function fails, it corrupts errno, on some platforms: Solaris 10.
• This function does not support many error values defined in <errno.h> on some platforms: MSVC 14.
• 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.
• This function reports failure for strerror_r(0, buf, len), although POSIX requires this to succeed, on some platforms: FreeBSD 8.2.
• This function produces a different string for 0 than strerror on some platforms: macOS 11.1.
• This function always fails when the third argument is less than 80 on some platforms: HP-UX 11.31.
• 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.
• 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.
• 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.

Portability problems not fixed by Gnulib:

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