strerror_r: fix OpenBSD behavior on 0 OpenBSD treats strerror_r(0,,) as a success, but with a message "Undefined error: 0"; while this is distinct from strerror_r(-1,,) returning "Unknown error: -1", it does not imply success. Meanwhile, if buf is short enough for ERANGE, then we can't use strstr to look for "Unknown" or "Undefined" in the resulting message, like we had been doing for strerror(). Fix this by shifting the burden - now the strerror-override code guarantees that 0 will have an override when needed. * lib/strerror-override.c (strerror_override): Also override 0 when needed. * lib/strerror-override.h (strerror_override): Likewise. * lib/strerror.c (strerror): Simplify, now that 0 override is done earlier. * lib/strerror_r.c (strerror_r): Likewise. * m4/strerror.m4 (gl_FUNC_STRERROR): Split detection of 0 behavior... (gl_FUNC_STRERROR_0): ...into new macro. * m4/strerror_r.m4 (gl_FUNC_STRERROR_R): Replace strerror_r if 0 is overridden. (gl_FUNC_STRERROR_R_WORKS): Avoid extra tests if 0 is broken. * modules/strerror-override (Files): Add strerror.m4. (configure.ac): Also provide override for 0 when needed. * doc/posix-functions/strerror.texi (strerror): Document this. * doc/posix-functions/perror.texi (perror): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>

Description:
strerror_override() function: provide strings for gnulib-specific errno values

Files:
lib/strerror-override.h
lib/strerror-override.c
m4/sys_socket_h.m4
m4/strerror.m4

Depends-on:
errno

configure.ac:
AC_REQUIRE([gl_HEADER_ERRNO_H])
AC_REQUIRE([gl_FUNC_STRERROR_0])
if test -n "$ERRNO_H" || test $REPLACE_STRERROR_0 = 1; then
  AC_LIBOBJ([strerror-override])
  gl_PREREQ_SYS_H_WINSOCK2
fi

Makefile.am:

Include:
"strerror-override.h"

License:
LGPLv2+

Maintainer:
all