view doc/posix-functions/dprintf.texi @ 39983:db717b5315cf

docs: mention printf %m considerations gcc -Wformat does NOT flag printf("%m") on a BSD system, even though it prints only "m" instead of the desired GNU/Linux behavior of the current errno value (you have to use -Wpedantic to flag it, but that's a rather heavy hammer). Still, it's easy enough (even if verbose) to write out strerror() usage directly, to the point that gnulib will probably never provide a module to guarantee %m everywhere. See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88270 * doc/glibc-functions/asprintf.texi (asprintf): Document that %m is not portable, and is easy enough to work around. * doc/glibc-functions/obstack_printf.texi (obstack_printf): Likewise. * doc/glibc-functions/obstack_vprintf.texi (obstack_vprintf): Likewise. * doc/glibc-functions/vasprintf.texi (vasprintf): Likewise. * doc/posix-functions/dprintf.texi (dprintf): Likewise. * doc/posix-functions/fprintf.texi (fprintf): Likewise. * doc/posix-functions/fwprintf.texi (fwprintf): Likewise. * doc/posix-functions/printf.texi (printf): Likewise. * doc/posix-functions/snprintf.texi (snprintf): Likewise. * doc/posix-functions/sprintf.texi (sprintf): Likewise. * doc/posix-functions/swprintf.texi (swprintf): Likewise. * doc/posix-functions/vdprintf.texi (vdprintf): Likewise. * doc/posix-functions/vfprintf.texi (vfprintf): Likewise. * doc/posix-functions/vfwprintf.texi (vfwprintf): Likewise. * doc/posix-functions/vprintf.texi (vprintf): Likewise. * doc/posix-functions/vsnprintf.texi (vsnprintf): Likewise. * doc/posix-functions/vsprintf.texi (vsprintf): Likewise. * doc/posix-functions/vswprintf.texi (vswprintf): Likewise. * doc/posix-functions/vwprintf.texi (vwprintf): Likewise. * doc/posix-functions/wprintf.texi (wprintf): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>
author Eric Blake <eblake@redhat.com>
date Thu, 29 Nov 2018 13:33:28 -0600
parents 73d60b1f9c96
children
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@node dprintf
@section @code{dprintf}
@findex dprintf

POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/dprintf.html}

Gnulib module: dprintf or dprintf-posix

Portability problems fixed by either Gnulib module @code{dprintf} or @code{dprintf-posix}:
@itemize
@item
This function is missing on many non-glibc platforms:
Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 11.3, Cygwin 1.5.x, mingw, MSVC 14, Interix 3.5, BeOS.
@end itemize

Portability problems fixed by Gnulib module @code{dprintf-posix}:
@itemize
@item
printf @code{"%f"}, @code{"%e"}, @code{"%g"} of Infinity and NaN yields an
incorrect result on some platforms:
Solaris 11.4.
@item
This function does not support the @samp{a} and @samp{A} directives on some
platforms:
glibc-2.3.6.
@item
printf @code{"%010f"} of NaN and Infinity yields an incorrect result (padded
with zeroes, or wrong capitalization) on some platforms:
Solaris 11.4.
@item
This function does not support precisions larger than 512 or 1024 in integer,
floating-point and pointer output on some platforms:
AIX 7.1.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
The @code{%m} directive is not portable, use @code{%s} mapped to an
argument of @code{strerror(errno)} (or a version of @code{strerror_r})
instead.
@item
Formatting noncanonical @samp{long double} numbers produces
nonmeaningful results on some platforms:
glibc and others, on x86, x86_64, IA-64 CPUs.
@item
When formatting an integer with grouping flag, this function inserts thousands
separators even in the "C" locale on some platforms:
NetBSD 5.1.
@item
On some platforms, this function does not set @code{errno} or the
stream error indicator on attempts to write to a read-only stream:
Cygwin 1.7.9.
@end itemize