Re: malloc realloc and pointers

On Thu, 29 Nov 2007 17:00:05 -0500, Kenneth Brody wrote:
ravi wrote:
2. With realloc(), if some pointer 'ptr' is pointing initially to a
perticular position in a buffer (char *buffer) then on performing a
realloc() on this buffer, what will be 'ptr' pointing to?

Three possibilities:

1) realloc() returns the same pointer, in which case ptr is still
valid, pointing to the newly-sized buffer.

According to DR #260, applied to realloc, even if memcmp proves the new
pointer is identical to the old pointer, you're not allowed to use them
interchangeably. If you pass a non-null pointer ptr to realloc, and it
doesn't return a null pointer, ptr is no longer valid.

(I do not believe the DR's conclusions can be drawn from any
interpretation of the actual standard, and in fact I believe some points
from the DR directly contradict explicit guarantees by the standard, but
that's just me.)
.

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