Package: manpages-dev Version: 3.74-1 Severity: wishlist Tags: patch Dear Maintainer, I recently caused a problem for myself when writing some C-code by making direct use of sys_errlist. I did this after reading the manpage for "perror". The code I wrote worked on Debian 7, but was not binary compatible with Debian 6, much to my surprise. Replacing my use of sys_errlist with strerror fixed the problem.
I have attached a suggested update to the perror (3) manpage. It is meant as an example, I have no strong feelings about my actual text. -- System Information: Debian Release: 8.1 APT prefers stable-updates APT policy: (500, 'stable-updates'), (500, 'stable') Architecture: amd64 (x86_64) Kernel: Linux 3.16.0-4-amd64 (SMP w/2 CPU cores) Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) Versions of packages manpages-dev depends on: ii manpages 3.74-1 manpages-dev recommends no packages. Versions of packages manpages-dev suggests: ii konqueror [man-browser] 4:4.14.2-1 ii man-db [man-browser] 2.7.0.2-5 -- no debconf information
.\" Copyright (c) 1994 Michael Haardt (mich...@moria.de), 1994-06-04 .\" Copyright (c) 1995 Michael Haardt .\" (mich...@cantor.informatik.rwth-aachen.de), 1995-03-16 .\" Copyright (c) 1996 Andries Brouwer (a...@cwi.nl), 1996-01-13 .\" .\" %%%LICENSE_START(GPLv2+_DOC_FULL) .\" This is free documentation; you can redistribute it and/or .\" modify it under the terms of the GNU General Public License as .\" published by the Free Software Foundation; either version 2 of .\" the License, or (at your option) any later version. .\" .\" The GNU General Public License's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" This manual is distributed in the hope that it will be useful, .\" but WITHOUT ANY WARRANTY; without even the implied warranty of .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the .\" GNU General Public License for more details. .\" .\" You should have received a copy of the GNU General Public .\" License along with this manual; if not, see .\" <http://www.gnu.org/licenses/>. .\" %%%LICENSE_END .\" .\" 1996-01-13 aeb: merged in some text contributed by Melvin Smith .\" (msm...@falcon.mercer.peachnet.edu) and various other changes. .\" Modified 1996-05-16 by Martin Schulze (j...@infodrom.north.de) .\" .TH PERROR 3 2014-05-28 "" "Linux Programmer's Manual" .SH NAME perror \- print a system error message .SH SYNOPSIS .B #include <stdio.h> .sp .BI "void perror(const char *" s ); .sp .B #include <errno.h> .sp .BI "char *" strerror(int errnum); .br .BI "int " sys_nerr ; .br .BI "int " errno "; /* Not really declared this way; see errno(3). */" .sp .in -4n Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .in .sp .IR sys_errlist , .IR sys_nerr : _BSD_SOURCE .SH DESCRIPTION The routine .BR perror () produces a message on the standard error output, describing the last error encountered during a call to a system or library function. First (if .I s is not NULL and .I *s is not a null byte (\(aq\\0\(aq)) the argument string .I s is printed, followed by a colon and a blank. Then the message and a new-line. To be of most use, the argument string should include the name of the function that incurred the error. The error number is taken from the external variable .IR errno , which is set when errors occur but not cleared when successful calls are made. To obtain the error message without the newline, call .IR strerror with the the argument .I errno . Traditionally one would access the error string through .IR sys_errlist "[]" indexed by .I errno . The largest message number provided in the table is .IR sys_nerr "\-1." Be careful when directly accessing this list because new error values may not have been added to .IR sys_errlist "[]." The use of this method is nowadays deprecated and you should use .IR strerror . When a system call fails, it usually returns \-1 and sets the variable .I errno to a value describing what went wrong. (These values can be found in .IR <errno.h> .) Many library functions do likewise. The function .BR perror () serves to translate this error code into human-readable form. Note that .I errno is undefined after a successful library call: this call may well change this variable, even though it succeeds, for example because it internally used some other library function that failed. Thus, if a failing call is not immediately followed by a call to .BR perror (), the value of .I errno should be saved. .SH CONFORMING TO The function .BR perror () and the external .I errno (see .BR errno (3)) conform to C89, C99, 4.3BSD, POSIX.1-2001. The externals .I sys_nerr and .I sys_errlist conform to BSD. .SH NOTES The externals .I sys_nerr and .I sys_errlist are defined by glibc, but in .IR <stdio.h> . .\" and only when _BSD_SOURCE is defined. .\" When .\" .B _GNU_SOURCE .\" is defined, the symbols .\" .I _sys_nerr .\" and .\" .I _sys_errlist .\" are provided. .SH SEE ALSO .BR err (3), .BR errno (3), .BR error (3), .BR strerror (3) .SH COLOPHON This page is part of release 3.74 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%http://www.kernel.org/doc/man\-pages/.
