Re: Goto considered dramafull

Oh yes, my intent would be to only use goto for truly exceptional
situations as in error cleanup, and in order to make *clearer* what is
going on.

A goto to end of routine to label e.g. "InputError:" with obvious return
ending that cleanup stanza - we aren't doing anything else here but
cleaning up and leaving.


On Sat, Aug 30, 2014 at 12:48 PM, Jose Da Silva <[email protected]> wrote:

> On August 30, 2014 06:46:17 AM Frank Trampe wrote:
> > I've never liked gotos because they break the nesting model and make
> > tiered clean-up difficult.
>
> You need to pay attention to nesting when you use goto.
>
> This is a very good example with nesting, look at this function:
> fontforgeexe/lookupui.c:SFDTrimUndoOldToNew
>
> error3SFDTrimUndoOldToNew: fclose(of);
> error2SFDTrimUndoOldToNew: fclose(nf);
> error1SFDTrimUndoOldToNew: fclose(retf);
> error0SFDTrimUndoOldToNew:
>     return 0;
> }
>
>
> This one is less complicated:
> gutils/gimagereadtiff.c:GImage *GImageReadTiff(char *filename) {
>
> errorGImageReadTiff:
>     fprintf(stderr,"Bad input file \"%s\"\n",filename );
> errorGImageReadTiffMem:
>     free(raster); free(ret);
>     TIFFClose(tif);
>     return( NULL );
> }
>
> > There are plenty of ways to avoid using them. One is to have each block
> > check for success or non-failure of the preceding block before doing its
> > thing. This also allows for more localized clean-up of block-specific
> > data.
>
> Agreed, other ways can be done, such as case statements or even nested
> while (0) loops, or something else:
>
> http://cvs.savannah.gnu.org/viewvc/aspell/prog/prezip.c?revision=1.10&root=aspell&view=markup
>
> example:
>   while (0) {
>     error_mem_c: retVal = 6; break;     /* memory alloc error */
>     error_out_c: retVal = 5; break;     /* output data error  */
>     /*           retVal = 3;               corrupt input      */
>   }
>
>
> ...however, having a goto pointing to the bottom of a function seems a bit
> cleaner and straight to the point.
>
> You shouldn't fear goto statements, just understand them.
>
> If you do gcc and output assembler source for any of the C files, you'll
> see
> a lot of goto statements for all sorts of statements, such as:
> if/then/else, case, while, etc...
>
>
>
>
>
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