Re: Goto considered dramafull

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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