Patch #2 to Pcomm v1.1

[Mike Khaw]

In article <7782 at bcsaic.UUCP> paula at bcsaic.UUCP (Paul Allen) writes:
>>
>>>! 	if (*lock_path != NULL && lock_path != NULL) {
>>
>>This only tests whether lock_path is legal *after* trying to use it!
> 
> I've now seen a couple postings about this bug, but nobody has got it
> right yet!  What has been missed is that C makes no guarantee about the <--
> order of expression evaluation.  The only safe way to perform this test <--
> is using two nested if statements.					  <--

from page 19 of K&R (1978 ed.)

	Expressions connected by && or || are evaluated
	left to right
	^^^^^^^^^^^^^
furthermore, "!=" has higher precedence than "&&" so

	if (lock_path != NULL && *lock_path != NULL)

is correct.

Mike Khaw
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