Re: pointer conversion

Charlton Wilbur wrote:
"M" == Malcolm McLean <regniztar@xxxxxxxxxxxxxx> writes:

M> You will be OK. char is always 1 byte. So casting an arbitrary
M> pointer to a char *, adding an exact multiple of the size of
M> the original type, and casting back is guaranteed to preserve
M> alignment.

I am not so sure about that; would you care to cite C&V, please, if
you claim that it's guaranteed by the standard?

He's wrong: it's not guaranteed. Simple example:

int target = 42;
int *ptr = &target + 1; /* "an arbitrary pointer" */
ptr = (int*)((char*)ptr + sizeof *ptr); /* U.B. */

If the original pointer points at an actual object of its
type (so it's not "arbitrary"), the conversion is safe.

--
Eric Sosman
esosman@xxxxxxxxxxxxxxxxxxxx
.

Relevant Pages

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