Is goto safe?

[John Woods]

In article <253 at usblues.UUCP>, tom at usblues.UUCP (Tom Markson) writes:
> Without getting into style issues, is the goto statement in C safe?

Yes, the goto statement is perfectly safe.  It's your programs that are in
trouble.

> For instance, If I do the following, am I guarenteed that no stack
> crashes will occur:

That is about the only evil which won't befall you.

> main() { { int i; i = 0; /* program adjusted for (near) maximum terseness */
> 	inside:	  printf("inside:%d\n",++i); goto outside; }
> 	   { int j; j = 0;
> 	outside:  printf("outside: %d\n",++j); goto inside; } }
> Question:  Is this always true.  Will it always run as expected with i and j
> incrementing from 0 to ...?
> 
It is not guaranteed.  Once you goto out of the scope of a variable, it is
not obligated to retain its value.  It would be legal for a compiler to use
the same space for both i and j, since their scopes are mutually exclusive.
Note, by the way, that j is never assigned an actual value in the sequential
execution of the program.  That it starts with a value of 0 is accidental.
-- 
John Woods, Charles River Data Systems, Framingham MA, (508) 626-1101
...!decvax!frog!john, john at frog.UUCP, ...!mit-eddie!jfw, jfw at eddie.mit.edu

Happiness is Planet Earth in your rear-view mirror.	- Sam Hurt