Re: [Valgrind-users] New skin available: Annelid, a pointer-misuse checker

[Erik C. <er...@ar...>]

On Mon, Sep 29, 2003 at 06:53:12PM +0000, Philippe Elie wrote:
> int main(void)
> {
>   char * p1 = malloc(1000);
>   char * p2 = malloc(1000);
>   printf("%p %p %p\n", p1, p2, &p1[p2 - p1]);
> 
>   p1[p2 - p1 + 1] = 0;  /* expect error here */

This isn't actually legal C code, and nor is the line above it.

It's section 6.3.6 in the ANSI standard, some other number in the
ISO standard.  I'm looking at the Herbert Schildt book "The Annotated
C Standard".

You are only allowed to subtract pointers if they are pointers 
into the same array object.

So it's a bit dodgy, though of course it is legal gcc, just not 
legal C.  And it could be legal some-other-language-that-you-compile-
and-feed-to-valgrind.

-- 
Erik Corry er...@ar...
A: Because it messes up the order in which people normally read text.
Q: Why is top-replying such a bad thing?
A: Top-replying.
Q: What is the most annoying thing in email?