Some subsurface notes from a week of diving

[Thiago Macieira]

Em seg 17 mar 2014, às 11:12:31, Linus Torvalds escreveu:
> The compiler is allowed to assume that the *result* of the arithmetic is
> not NULL, because pointer arithmetic is only well-defined if it stays
> within an object, and that explains the offsetof thing you point to (since
> that very much uses the result). Even then, a compiler that actually
> miscompiles the traditional format is just crap.

Indeed:

struct D { int i; int j; }; 
int f(struct D *d) 
{
	int *p = &d->j; 
	if (!p)
		return -1; 
	return *p; 
}

Clang 3.4 removes the check for !p. ICC 14.0 and GCC 4.9 don't.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
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