Another quick question about a C function, this time its strcpy(). My question is, is there a limit on the size of the strings? I only ask because if I try to copy a string larger than 12 characters it causes an invalid page fault in kernel32.dll.

I'm probably doing something wrong but I vaguely recall seeing something about there being a maximum size to strings that can be copied and was dictated by the operating system. And yes I've checked the standard c library reference, and it mentions nothing about a limit. If anyone could shed some light on this I'd appreciate it :).

You'd be after strdup, strcpy needs the ram to be allocated before hand.

Yeah I *thought* I had allocated the right amount of space for strcpy() yet as it turns out, I was allocating 4 bytes less than what I needed. I looked at strdup() in my book and considered that and then found that its non-ANSI :|. Oh well writing your own version of it wouldn't be too much extra work.

Oh and my compiler (lcc-win32) doesn't appear to have strdup() either.

Yeah, you have to already have allocated a buffer to use for strcpy. Usually thats not too much of a hassle though. If you know how long the string is gonna be before hand (or you know the maximum size it could be), its not a problem, if you dont you could count the number of characters in the source string and then use something like malloc or calloc to dynamically allocate the memory. You could use something like

char *strPtr, *destString;
int charCount;

for(charCount = 0, strPtr = srcString; *strPtr != '\0'; strPtr++, charCount++);
destString = (char *)calloc(charCount+1, sizeof(char));
strcpy(destString, srcString);


That is of course assuming srcString (the source string you want to copy) is null terminated, which it should be if you're using any str functions on it anyway. I can't remember if I have the arguments for strcpy and calloc around the right way, but I'm sure you can figure it out if I dont. Its 1am and I'm going to bed and I couldn't be bothered looking it up to make sure I'm right :)

Oh well I worked around another problem I was having (not related to the strcpy() problem). Its probably just one big kludge but I don't care it works perfectly. When I release the source you can read it and tell me how bad it is :).

strcpy is a mad function
it just keeps putting characters in the destination buffer until it hits a null in the source buffer..

i dun do much c, but i know that malloc is a bitch to use...

don't know about calloc but from what khel has shown looks like it could be wicked, dynamically allocating memory

Heh C was such a bitch to write. Whenever I went to get help people were like "what libraries are you using" and I was like "err I'm a noob i have nfi"

char *strPtr, *destString;
int charCount;

for(charCount = 0, strPtr = srcString; *strPtr != '\0'; strPtr++, charCount++);
destString = (char *)calloc(charCount+1, sizeof(char));
strcpy(destString, srcString);

No need for the for loop. use strlen().

int charCount = strlen(srcString);

or

destString = (char *)malloc(strlen(srcString) + 1);

strcpy() blindly overwrites anything in the destination buffer anyway, so using calloc is a waste. calloc is basically a malloc followed by filling the buffer with zeroes. Just use malloc and let strcpy overwite the buffer.

A very basic version of strcpy()...

while ((*dest++ = *src++) != 0) {;}

Hah, I never even knew there was a strlen function in Ansi C :( Woe is me.

Really!? /me pats C book :P

'C' comes after 'B'.

But B does not come after A.

hunter i thought you did a course in c programming
and you don't even know how to use strcpy() properly??

Yeah, I spose I should get a C book one day, all I ever use for reference is the MSDN cds, which are good, but are kinda hard to browse through and read like a book. Books are good like that, even if you're not looking for anything in particular you can just flick through them and most of the time you find something interesting you didn't know.

I've also noticed sometimes when you search the MSDN help thing it gives you really really stupid results :(

go the good old "A Book on C" :)

hunter i thought you did a course in c programming
and you don't even know how to use strcpy() properly??

I did a couple of modules (Intro to C - eg hello world stuff and Applications using C/C++ which was hash tables, I/O communications and a few other things) in a course which isn't even a programming course... its to broaden your knowledge, not give you a full overview of the entire C language and its standard library functions.

Khel: Yeah that's why I like books - they go anywhere and you don't need a computer to view them. And reading a book for a few hours doesn't hurt your eyes like reading text on a monitor does. And yeah you do find a lot of interesting tidbits when flipping through a book.