Re: [gnugo-devel] cygwin sscanf problem in gtp.c

[Trevor Morris]

The space before the %n is intentional, as the sscanf is trying
to grab the whitespace.  However, VC has the " " match \n whereas 
cygwin doesn't, causing the problem.

At 03:23 PM 10/26/2001 +0100, Dave Denholm wrote:
>Trevor Morris <address@hidden> writes:
>
>> Here's a test file that shows how gtp.c fails.
>> In short, the " %s %n" construct isn't working as expected.  In the
>> last sscanf, 1 is returned, but n is not set.  This causes very
>
>Is the before %n intentional - it's saying match a string as %s,
>then if it can match some whitespace, put the number of characers
>consumed into %n. Since scanf stops as soon as the match fails,
>it could satisfy the %s, but then if it fails to match the whitespace
>it will return 1 without filling in the %n.
>
>(Or maybe this is implementation dependent ?)
>
>dd
>
>
>
>> bad behavior in gtp.c (line 97, etc.) [specifically p += n].
>> Is this specific to cygwin, or do other platforms have this problem
>> too?
>> 
>> const char *db = "dragon_data black\n";
>> const char *d1 = "dragon_data\n";
>> 
>> char command[1024];
>> int n=-1,r;
>> 
>> dump(const char *s, char*command) {
>>   printf("%d %d '%s' '%s'\n", r, n, command, s);
>>   n = -1 ;
>> }
>> 
>> 
>> main() {
>>   r = sscanf(d1, " %s%n", command, &n);
>>   dump(d1, command);
>>   r = sscanf(db, " %s%n", command, &n);
>>   dump(db, command);
>>   r = sscanf(d1, " %s%n", command, &n);
>>   dump(d1, command);
>> 
>>   r = sscanf(d1, " %s %n", command, &n);
>>   dump(d1, command);
>>   r = sscanf(db, " %s %n", command, &n);
>>   dump(db, command);
>>   r = sscanf(d1, " %s %n", command, &n);
>>   dump(d1, command);
>> }
>> 
>> cygwin (gcc) output:
>> 1 11 'dragon_data' 'dragon_data
>> '
>> 1 11 'dragon_data' 'dragon_data black
>> '
>> 1 11 'dragon_data' 'dragon_data
>> '
>> 1 -1 'dragon_data' 'dragon_data
>> '
>> 1 12 'dragon_data' 'dragon_data black
>> '
>> 1 -1 'dragon_data' 'dragon_data
>> '
>> 
>> 
>> VC output:
>> 1 11 'dragon_data' 'dragon_data
>> '
>> 1 11 'dragon_data' 'dragon_data black
>> '
>> 1 11 'dragon_data' 'dragon_data
>> '
>> 1 12 'dragon_data' 'dragon_data
>> '
>> 1 12 'dragon_data' 'dragon_data black
>> '
>> 1 12 'dragon_data' 'dragon_data
>> '
>> 
>> 
>> 
>> 
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>> gnugo-devel mailing list
>> address@hidden
>> http://mail.gnu.org/mailman/listinfo/gnugo-devel
>
>
>dd
>-- 
>address@hidden          http://www.insignia.com
>
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