Order of evalution of expressions.

[Rob McMahon]

In article <6398 at castle.ed.ac.uk> elee24 at castle.ed.ac.uk (H Bruce) writes:
>Is the line
>
>value = *ptr - *ptr++;
>
>sensible C ?
>In other words is there a specified order of evaluation of expressions ?

Absolutely not, no.

>Would the following lines be optimized by a compiler (so that value is
>not loaded twice) ?
>
>value = *ptr;
>value -= *ptr++;

Well, gcc optimizes this to

	ptr++;
	value = 0;

I suspect your code may be wrong :-)

Rob
--
UUCP:   ...!mcsun!ukc!warwick!cudcv	PHONE:  +44 203 523037
JANET:  cudcv at uk.ac.warwick             INET:   cudcv at warwick.ac.uk
Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England