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Re: Undefined qsort behavior

On Thu, Dec 05, 2002 at 02:44:55PM -0200, Miguel A. Osorio wrote:

> material/texture). But the qsort man page says: "If  two  members
> compare as equal, their order in the sorted array is undefined". So my
> question is this: this "undefined order" still groups equal elements
> together, or is the undefined *really* undefined ? For instance, if I
> have an array: 4 2 3 1 2 4, do I *always* get: 1 2 2 3 4 4 ?

"Undefined" has a very technical defintion. It means, very literally,
the behaviour has not been specified in ANY WAY and the routine is
free to do as it pleases with it.

It could vary between library implementations, between machines with
different CPUs, it could vary on initial conditions, sizes of the
arrays; absolutely ANYTHING. And when it does so, you have no

Testing it on your machine and using that undefined bahaviour is
asking for it not to work somewhere else later. You might as well
raise the bug against that bit of code yourself.

Undefined means "don't use this, it might stop working like it does at
any point in time".