Re: [PATCH] PR3609

[Gabriel Dos Reis <gdr at codesourcery dot com>]

Jakub Jelinek <jakub@redhat.com> writes:

[...]

| > 
| > Note that `"foo" + 10' is *undefined*, but
| > `(char*)((size_t)"foo" + 10)' is *implementation-defined*.
| > 
| > I think the resolution everyone wants is that the implementation-defined
| > behavior for string-constant + variable offset is that the result
| > is undefined, even when there are casts involved.
| > 
| > I think is not in the spirit of the standard.  For example, the C++
| > standard defines implementation-defined behavior as:
| > 
| >   behavior,  for  a well-formed program construct and correct data, that
| >   depends on the implementation and that each implementation shall docu-
| >   ment.
| 
| But I think the most natural implementation-defined behaviour for this is
| that it is the same thing as *("foo" + 10), whatever casts you do you're still
| referencing something beyond end of an object.

I disagree.  The most natural implementation I see is to do exactly what
the programmer wrote:

	1) address -> integer mapping
	2) compute the addition
	3) integer -> adress mapping

| Anyway, so that we don't spend too much energy on this, following patch
| only optimizes if the string was not casted to non-pointer type before the
| addition, so Franz's testcase works and no gcc testcases need to be changed.

Thanks,

-- Gaby