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AIva1110 · Posted: Wed Sep 23, 2009 6:19 am Post subject: StrCmp

if(!strcmp(flight[t].from, from) && !strcmp(flight[t].to, to))

Anybody knows why statements in if are not returning true in this statement, since all parameters are correct and checked before execution.

Strcmp returns 0, in c anything but 0 is true, that is why ! statements are used.

Slugsnack · Posted: Wed Sep 23, 2009 6:26 am Post subject:

we can't check until you give us more code. i suggest you debug it. the computer can not be wrong. if it's returning a result you are not expecting it must be an error on your side

AIva1110 · Posted: Wed Sep 23, 2009 6:46 am Post subject:

Problem is im in library atm so i cant use olly here, there isnt much point in posting anything else because functions are independent, only 2 parameters are passed to this function declaration is : int match(char *from,char *to)
after that i check parameters with printf() to see if they were passed correctly, they are. After this follows if statement. Here, main part of the function checks excluded. I checked what's t and what is passed from array as well.

Slugsnack · Posted: Wed Sep 23, 2009 7:10 am Post subject:

okay before the strcmps, add a MessageBox which display all 4 compared strings. I'm guessing what's happening is that your match function is returning 0 ?

i'm also guessing 'flight' is extern, i don't see it anywhere in your function ?

AIva1110 · Posted: Wed Sep 23, 2009 7:22 am Post subject:

Flight is an array of structures, I'm comparing it's member .from with parameter "from" which is passed to function. I checked everything that's being compared, it prints correct strings. Now I tried printing return value of StrCmp and it just crashes the program, probably because I don't know how to print it lol. Any ideas how to print return value correctly? google search didn't yield much results.

Slugsnack · Posted: Wed Sep 23, 2009 7:37 am Post subject:

Deltron Z · Posted: Wed Sep 23, 2009 7:39 am Post subject:

What if one of the string returns a non-zero value? which means, the strings are different and the result of x & 0 = 0, then when you NOT it then you'll get 1 even though only one of the strings is different than the other.

You should do:
if (strcmp(..) == 0 && strcmp(..) == 0)
......

Slugsnack · Posted: Wed Sep 23, 2009 7:54 am Post subject:

yes, his code in the first post was correct. i did not notice that it was different in the code example he gave though

AIva1110 · Posted: Wed Sep 23, 2009 8:26 am Post subject:

That code i gave has a mistake i left it doing experiments, assume code from first post is used.

I tried testing return value of strcmp using printf() as slugsnack suggested and it returned wrong result, then I checked flight[t].from against from passed to a function and flight[t].from has string from the bottom of database when it was supposed to have it from the top, the odd thing is that top and bottom entries match and i didn't notice this until now. When checking second string program crashed because they were incorrect...now it's fixed. Thanks for help everyone.