About Xalloc()/Xfree() function used in liblbxutil library.

Joerg Sonnenberger joerg at britannica.bec.de
Tue Sep 18 05:09:13 PDT 2007

On Mon, Sep 17, 2007 at 02:01:21PM +0900, Tadashi Koike wrote:
> On this research, I understood that Xalloc()/Xfree() are same as
> malloc()/free() except that an memory allocation size be specified
> as ZERO  by caller. But sorry I couldn't understand a difference of
> behavior on failure.

malloc(0) can implement one of two behaviours according to POSIX:
(a) It can return NULL.
(b) It can return a unique pointer.

It is up to the implementation which one it does. A bunch of code in X11
depends on the second behaviour and the easiest way to force that is to
turn malloc(0) into malloc(1). That is precisely what this code does.


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