NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/8145

Internet Message Format | 1996-08-05 | 2.0 KB

Path: news.clark.net!usenet
From: [e-mail] (yom)
Newsgroups: comp.lang.c
Subject: Re: more problems with qsort
Date: 28 Feb 1996 03:47:58 GMT
Organization: Your Organization
Message-ID: <4h0j9e$[e-mail]>
References: <[e-mail]>
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Since you're trying to sort a char**, the qsort function call must
look like this:

qsort(array,lines,sizeof(char **),(int (*)(void *,void *)) compare);

And your compare function must be defined like this:

int compare(char **a,char **b) {return strcmp(*a,*b);}

The use of sizeof operator ensures that this code will be compatible
with 64 bit architecture such as AXP/OSF.

Song ([e-mail])

In article <[e-mail]>, [e-mail]
says...
>
>Hi folks --
>
>after reading the FAQ entries about qsort, I thought I had my problem
>licked, but it seems not.
>
>Architecture: SunOS 4.1.3 with ANSI-C compiler.
>
>I'm doing some file manipulation and between steps A and B, I need to
sort.
>For various reasons, I don't want to popen() to the sort utility--I
want to
>use qsort.  Here's what I'm doing:
>
>   get number of lines in the file
>   (char**)malloc with enough room for all lines
>   for each line in the file {
>     (char*)malloc(90)  /* 90 is enough room for each line in file */
>     copy each line into the newly malloc()ed space
>     point a (char**) to the newly malloc()ed space
>   }
>
>so now I should have "lines" number of pointers to pointers to char,
>each one pointing to 90 bytes containing a line in the file.
>
>So, I call qsort(array[0], lines, 90, compare)
>where compare is my comparison function -- prepared as discussed
>in the FAQ.  Now all I get are core dumps during the call to qsort().
>:-)
>
>The core dump isn't in my compare routine -- it's somewhere else in
>the qsort() function according to dbx -- so I'm sure it's a problem
>setting up my data.
>
>Any tips?  Much appreciation in advance,
>Regards,
>Jim