effect of free()

[T. William Wells]

In article <3777 at buengc.BU.EDU> bph at buengc.bu.edu (Blair P. Houghton) writes:
: In article <320 at cubmol.BIO.COLUMBIA.EDU> ping at cubmol.UUCP (Shiping Zhang) writes:
: I guess the word is, once space is freed, don't even try to get data
: out of it.  It's risky at least, and nonportable without question.

Actually, things are worse than that: once the space is freed, don't
even *look* at the pointer. For example, the following code fragment
is nonportable:

	char    *ptr;

	ptr = malloc(1);
	...
	free(ptr);
	...
	if (ptr == 0) ...

The if might cause a trap when the value of ptr is accessed.

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