🚀 go-pugleaf

>Robert C Shields (rcshlds@mailserv.mta.ca) wrote:
> I am trying to get a feel for how people feel about the GOTO statement... 
>: please post..
>
>Somebody at school saw a goto in my code and freaked. Then again, this 
>person (who shall remain nameless) is used to machines with 100MB of 
>memory and dual SPARC CPU's. I on the other hand am not.

>The code in question was a routine that allocated various resources. 
>Below is an example of such a thing (this time using OS/2 & C). I use Goto's 
>to clean up the mess in the event of an error. 
>
>Example for a good use of goto:
>---                    ????
>------------------------------------------------------------------------------
>   HEV    hev1, hev2, hev3;     /* Event semaphores */
>   HMTX   hmtx;                 /* Mutex semaphore  */ 
>   void  *ptr;              

>   if (!DosCreateEventSem(0, &hev1, 0, FALSE))
>       goto hev1_failed;
>
>   if (!DosCreateEventSem(0, &hev2, 0, FALSE))
>       goto hev2_failed;

>   if (!DosCreateEventSem(0, &hev3, 0, FALSE))
>       goto hev3_failed;
>
>   if (!DosCreateMutexSem(0, &hmtx, 0, FALSE))
>       goto hmtx_failed;
>
>   if ((ptr = malloc(SOME_SIZE)) == NULL)
>       goto malloc_failed;
>
>   /* Do some stuff here */
>   return TRUE; /* We did okay */
>
>malloc_failed:
>   DosCloseMutexSem(hmtx);
>hmtx_failed:
>   DosCloseEventSem(hev3);
>hev3_failed:
>   DosCloseEventSem(hev2);
>hev2_failed:
>   DosCloseEventSem(hev1);
>hev1_failed:
>   return FALSE;


The above is NOT an example of a good use for the goto statement. A lot
of programmers hate goto with fanatical fervor. I personally feel they 
can make for better code in certain situations. The first situation would
be to eliminate multiple return statements. A goto branch to a SINGLE label
is greatly preferable to multiple return statements with several exit points.
A subroutine with a single exit point is a lot easier to maintain than one 
with several exit points. The second situation would be to break out of a 
nested loop. The alternative to a goto in this situation is to use of flag
of some kind (while(more_data)), but this tends to make the code larger and
harder to read. Some more guidelines to follow for goto's are:

 DON'T use a goto unless it's the only solution to the problem.
 You have many alternatives to a goto in your above code. 

 A subroutine should have at most one label.

 All goto's should be above that label in the code.

 The label should be in the same code block or at a more outer nesting level
 than the goto itself.

Your code could be easily reorganized to not use a goto.

-John