Difference between revisions of "Goto"
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Instead of placing ''everything'' in a “success”-branch, a couple <syntaxhighlight enclose="none" lang="pascal">goto</syntaxhighlight> instructions were chosen. | Instead of placing ''everything'' in a “success”-branch, a couple <syntaxhighlight enclose="none" lang="pascal">goto</syntaxhighlight> instructions were chosen. | ||
| − | [[ | + | == see also == |
| + | * [[sGoto|<syntaxhighlight lang="pascal" enclose="none">{$goto}</syntaxhighlight> compiler directive]] | ||
| + | |||
| + | [[Category:Pascal]] | ||
[[Category:Control Structures]] | [[Category:Control Structures]] | ||
Revision as of 19:49, 7 March 2018
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goto is an unconditional jump to a previously declared label (either before or after the goto command).
Usage of goto in high-level programming languages such as Pascal is highly discredited, since control structures of all sorts are available.
The last situation a goto is agreed with bad grace is a significant system error, where a “graceful exit” is better than causing a system breakdown.
As an example, here an excerpt from FPC's code base rtl/inc/extres.inc:
324procedure InitResources;
328label ExitErrMem, ExitErrFile, ExitNoErr;
329begin
339 ResHeader:=GetMem(sizeof(TExtHeader));
340 if ResHeader=nil then goto ExitErrFile;
366 goto ExitNoErr;
367
368 ExitErrMem:
369 FreeMem(ResHeader);
370 ResHeader:=nil;
371 ExitErrFile:
372 {$I-}
373 Close(fd);
374 {$I+}
375 ExitNoErr:
376end;
According to the value of returnNilIfGrowHeapFails getMem possibly may return nil.
Instead of placing everything in a “success”-branch, a couple goto instructions were chosen.
