From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2003-08-27 23:43:36
On Wed, Aug 27, 2003 at 11:22:14PM +0200, Groepaz wrote:
> ooooohhh ... so sth like *(char*)0x8000=0 is infact undefined and just happens
> to access memory address 0x8000 on a lot of machines/targets (but it could
> access address 0x1234 on some other imaginary one) ?
Yes, with one minor correction: It is not undefined, but "implementation
defined".
"unspecified behavior" means that the standard provides several
possibilities, where the implementation is free to choose one of them.
"implementation defined behavior" means that the implementation has to
document the way, a feature is implemented.
"undefined behavior" means that there are no restrictions, so the compiler may
generate predictable results, generate wrong code, crash, start world war III
or whatever.
In the case of "*(char*)0x8000=0", compiler writers seem to agree that this
notation is the natural one to access the contents of the memory at address
0x8000 - but this is not required by the standard.
All three do mean that a program using such a feature is non portable (which
is obvious in the case of *(char*)0x8000=0).
Regards
Uz
--
Ullrich von Bassewitz uz_at_musoftware.de
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