Mercurial > hg > octave-kai > gnulib-hg
changeset 5566:fe0bf8f0751e
standards update
author | Karl Berry <karl@freefriends.org> |
---|---|
date | Thu, 30 Dec 2004 22:56:28 +0000 |
parents | 3dc56d504a02 |
children | 946a798ce6cd |
files | doc/standards.texi |
diffstat | 1 files changed, 43 insertions(+), 30 deletions(-) [+] |
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--- a/doc/standards.texi +++ b/doc/standards.texi @@ -3,7 +3,7 @@ @setfilename standards.info @settitle GNU Coding Standards @c This date is automagically updated when you save this file: -@set lastupdate December 19, 2004 +@set lastupdate December 30, 2004 @c %**end of header @dircategory GNU organization @@ -2685,38 +2685,51 @@ write(file_descriptor, &c, 1); @end example -When calling functions, you need not worry about the difference between -pointers of various types, or between pointers and integers. On most -machines, there's no difference anyway. As for the few machines where -there is a difference, all of them support Standard C prototypes, so you can -use prototypes (perhaps conditionalized to be active only in Standard C) -to make the code work on those systems. - -In certain cases, it is ok to pass integer and pointer arguments -indiscriminately to the same function, and use no prototype on any -system. For example, many GNU programs have error-reporting functions -that pass their arguments along to @code{printf} and friends: +It used to be ok to not worry about the difference between pointers +and integers when passing arguments to functions. However, on most +modern 64-bit machines pointers are wider than @code{int}. +Conversely, integer types like @code{long long int} and @code{off_t} +are wider than pointers on most modern 32-bit machines. Hence it's +often better nowadays to use prototypes to define functions whose +argument types are not trivial. + +In particular, if functions accept varying argument counts or types +they should be declared using prototypes containing @samp{...} and +defined using @file{stdarg.h}. For an example of this, please see the +@uref{http://www.gnu.org/software/gnulib/, Gnulib} error module, which +declares and defines the following function: @example -error (s, a1, a2, a3) - char *s; - char *a1, *a2, *a3; +/* Print a message with `fprintf (stderr, FORMAT, ...)'; + if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM). + If STATUS is nonzero, terminate the program with `exit (STATUS)'. */ + +void error (int status, int errnum, const char *format, ...); +@end example + +A simple way to use the Gnulib error module is to obtain the two +source files @file{error.c} and @file{error.h} from the Gnulib library +source code repository at +@uref{http://savannah.gnu.org/cgi-bin/viewcvs/gnulib/gnulib/lib/}. +Here's a sample use: + +@example +#include "error.h" +#include <errno.h> +#include <stdio.h> + +char *program_name = "myprogram"; + +FILE * +xfopen (char const *name) @{ - fprintf (stderr, "error: "); - fprintf (stderr, s, a1, a2, a3); + FILE *fp = fopen (name, "r"); + if (! fp) + error (1, errno, "cannot read %s", name); + return fp; @} @end example -@noindent -In practice, this works on all machines, since a pointer is generally -the widest possible kind of argument; it is much simpler than any -``correct'' alternative. Be sure @emph{not} to use a prototype for such -functions. - -If you have decided to use Standard C, then you can instead define -@code{error} using @file{stdarg.h}, and pass the arguments along to -@code{vfprintf}. - @cindex casting pointers to integers Avoid casting pointers to integers if you can. Such casts greatly reduce portability, and in most programs they are easy to avoid. In the @@ -3782,9 +3795,9 @@ social and ethical problem, and the point of GNU is to solve that problem. -The GNU definition of free software is found in -@url{http://www.gnu.org/philosophy/free-sw.html}, with a list of -important licenses and whether they qualify as free in +The GNU definition of free software is found on the GNU web site at +@url{http://www.gnu.org/philosophy/free-sw.html}. A list of +important licenses and whether they qualify as free is in @url{http://www.gnu.org/licenses/license-list.html}. The terms ``free'' and ``non-free'', used in this document, refer to that definition. If it is not clear whether a license qualifies as free