Re: Are bad developer libraries the problem with M$ software?

> From: "" <cdavison@nucleus.com>
>
> ----- Original Message -----

What is needed is the number of elements in mystr, not the length of the string stored there. On an array sizeof() will give the total size of the array, so it is a correct usage.

> > Perhaps we should start development of a standardized 'safe' header file

Not safe, though you've merely overwritten the end by one and with a \0, you've still overflowed, game over.

Perhaps the approach should be to make all the functions consistant and take their arguments in more convenient forms? Lets use the premise that if you're working with dynamically allocated strings you're probably storing the number of elements in the array.

Given this premise making all functions take the number of elements in the destination array including the trailing \0 (strncpy() style) and thereby not needing to subtract 1 every time you use the function is the way to go (this is also the safe way to go, since if somebody loses track of how the length is taken care of they're likely to leave a character unused rather than overflowing by 1).

Then strncat() should take the size of the destination (again including the \0), because it is more likely that the total size is stored rather than the free space. Also given the total space it is very easy for strncat() to internally compute the free space (when searching for the end of the string, simply decrement the space counter) this also has better performance since you don't need to use strlen() first (if you already know where the end is, then use strncpy()).

The example safe_strncat() doesn't work in the first place either:

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struct string_t {

	unsigned long size;
	char str[1];

Passing size will be ignored because sizeof(string_t.str) will always evaluate to 1 (*!#%#%# ANSI disallowing zero length arrays!) and is therefore smaller than the 'len' argument. Worse though is that because of subtracting 1 to compensate for the \0 you've got 0, now unless strlen() is 0 you've ended up with a value that is almost certainly rather larger than the length of the actual array.

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