Path: csiph.com!eternal-september.org!feeder.eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: C idioms
Date: Thu, 11 Oct 2018 10:38:23 -0700
Organization: None to speak of
Lines: 53
Message-ID: <ln7eioxu28.fsf@kst-u.example.com>
References: <36d546c5-b471-45fc-b87a-8ebebdc0c0b7@googlegroups.com> <87pnwlhp1q.fsf@bsb.me.uk> <54e12132-07e7-432f-95e8-f292f5f5bdad@googlegroups.com> <pbfu8f-mil.ln1@gangtai.home.grep.be> <ppi95o$kfu$2@news.xmission.com> <j12vD.4060$%T7.287@fx30.am4> <87y3b6u3ev.fsf@bsb.me.uk> <fdcvD.26161$aw7.13806@fx04.am4> <877eiptkjj.fsf@bsb.me.uk> <KpxvD.26024$eN2.24618@fx07.am4> <dEGvD.13159$vf.9799@fx05.am4> <87zhvksdz6.fsf@bsb.me.uk> <eoKvD.95780$fE2.59582@fx30.iad>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Injection-Info: reader02.eternal-september.org; posting-host="2e98a4ae6d37959bf94050b86ea67cbf"; logging-data="20591"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+Ie26/utvqQ4NdVOkIpAIB"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux)
Cancel-Lock: sha1:sAILKdwHLdLO65UTkoJ7EwU1Js0= sha1:Q6NeUUPuZuTEYTxlEDWrCUvTACw=
Xref: csiph.com comp.lang.c:136668

scott@slp53.sl.home (Scott Lurndal) writes:
> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>>Bart <bc@freeuk.com> writes:
>
>>> int main(void) {
>>>     FILE *f;
>>>     char *infile = "/mx/mm.pro";
>
> Bad programmer!  Pass it in to main as an argument.

It depends.  If it's passed as an argument, then whoever runs the
program has to know that "/mx/mm.pro" is the right name.  There could be
an overridable default.

[...]

>>>     char *ptr;
>>>
>>>     f = fopen(infile,"r");
>>>
>>>     if (f == NULL) {
>>>         printf("Can' open %s\n", infile);
>
> Why can't you open it?
>
>            printf("Unable to open '%s':%s\n", infile, strerror(errno));

The standard doesn't require fopen() to set errno on failure (though I
think it does on most systems, and POSIX requires it).

[...]

>>Most C programmers would probably write
>>
>>  while (*ptr == ' ' || *ptr == '\t')
>>      ++ptr;
>
> Or better:
>
>     while (isspace(*ptr)) ptr++;

Or better:

>     while (isspace((unsigned char)*ptr)) ptr++;

If plain char is signed and *ptr happens to be negative (and not equal
to EOF), isspace(*ptr) call has undefined behavior.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"