tarr-michael@CS.Yale.EDU (michael tarr) (07/09/90)
On an error condition I wish to immediately stop processing a large file and break out of about 10 routines that have been calling each other and return to my main event loop. Is there any way to do this without passing and error flag to each of the calling routines? tarr@cs.yale.edu
puklich@plains.UUCP (Blayne Puklich) (07/10/90)
tarr-michael@CS.Yale.EDU (michael tarr) wrote in article Breaking out of a series of routines: >On an error condition I wish to immediately stop processing a large file >and break out of about 10 routines that have been calling each other and >return to my main event loop. Is there any way to do this without >passing and error flag to each of the calling routines? You can use the setjmp() and longjmp() pair of functions to do this, assuming you're using C. I'm not very familiar with these, but with a bit of experimentation and manual reading, you should be able to figure out how to use these functions. If you're using Pascal, probably a good way to do this is to pass a return code back up through each function (make them functions). Then each and every call to the functions would be a test for a return code. This really isn't as painful as it may seem like. Pascal function return values are generally placed in a register (D0 if I remember right), so a test wouldn't be too time-consuming. ||+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++|| || Blayne Puklich puklich@Plains.NoDak.EDU "I think I'm going bald..." || || NDSU, Fargo, ND (701) 237-4408 -- Rush, Caress of Steel, || || 1975 || ||-------------------------------------------------------------------------||
jeremyr@cs.qmw.ac.uk (Jeremy Roussak) (07/10/90)
In article <25526@cs.yale.edu> tarr-michael@CS.Yale.EDU (michael tarr) writes: > >On an error condition I wish to immediately stop processing a large file >and break out of about 10 routines that have been calling each other and >return to my main event loop. Is there any way to do this without >passing and error flag to each of the calling routines? You could use signals, which are described in TechNote 88. They are provided for just this purpose. Jeremy Roussak
mnykanen@cc.helsinki.fi (07/10/90)
In article <5252@plains.UUCP>, puklich@plains.UUCP (Blayne Puklich) writes: > tarr-michael@CS.Yale.EDU (michael tarr) wrote in article Breaking out of a > series of routines: >>On an error condition I wish to immediately stop processing a large file >>and break out of about 10 routines that have been calling each other and >>return to my main event loop. Is there any way to do this without >>passing and error flag to each of the calling routines? .stuff on C's set/longjmp() deleted.. > If you're using Pascal, probably a good way to do this is to pass a return > code back up through each function (make them functions). Then each and > every call to the functions would be a test for a return code. This really > isn't as painful as it may seem like. Pascal function return values are > generally placed in a register (D0 if I remember right), so a test wouldn't > be too time-consuming. In Pascal a GOTO (yuck!) should suffice, at least as defined in the standard. Since a Pascal GOTO is *not* just a branch instruction (it even manages the run-time stack frames!) many microcomputer compilers do not conform, though. But I too recommend functions returning error codes on aesthetic grounds: they would make error recovery a part of normal program behaviour, not 'an act of god' miraculously affecting the control flow. -- Matti Nyk{nen CS Student at Helsinki U, Finland email: mnykanen@cc.helsinki.FI The best opinions available; get them while they're hot!
mxmora@unix.SRI.COM (Matt Mora) (07/10/90)
In article <2745.2699a0d0@cc.helsinki.fi> mnykanen@cc.helsinki.fi writes: >In article <5252@plains.UUCP>, puklich@plains.UUCP (Blayne Puklich) writes: >> tarr-michael@CS.Yale.EDU (michael tarr) wrote in article Breaking out of a >> series of routines: >>>On an error condition I wish to immediately stop processing a large file >>>and break out of about 10 routines that have been calling each other and >>>return to my main event loop. Is there any way to do this without >>>passing and error flag to each of the calling routines? >.stuff on C's set/longjmp() deleted.. [more stuff deleted] >In Pascal a GOTO (yuck!) should suffice, at least as defined in the >standard. Since a Pascal GOTO is *not* just a branch instruction (it >even manages the run-time stack frames!) many microcomputer compilers do >not conform, though. But I too recommend functions returning error codes I might be wrong but I think Apple has come up with something to do this already. Its called Signals. (and I know Apple probably didn't come up with it, maybe its from the unix world) Macintosh Technical Notes #88 describes the signals mechanism. I havn't used or studied it very much but it might be what you need. >Matti Nyk{nen -- ___________________________________________________________ Matthew Mora | my Mac Matt_Mora@sri.com SRI International | my unix mxmora@unix.sri.com ___________________________________________________________
urlichs@smurf.sub.org (Matthias Urlichs) (07/11/90)
In comp.sys.mac.programmer, article <5252@plains.UUCP>,
puklich@plains.UUCP (Blayne Puklich) writes:
< tarr-michael@CS.Yale.EDU (michael tarr) wrote in article Breaking out of a
< series of routines:
< >On an error condition I wish to immediately stop processing a large file
< >and break out of about 10 routines that have been calling each other and
< >return to my main event loop. Is there any way to do this without
< >passing and error flag to each of the calling routines?
<
< You can use the setjmp() and longjmp() pair of functions to do this, assuming
< you're using C. I'm not very familiar with these, but with a bit of
< experimentation and manual reading, you should be able to figure out how
< to use these functions.
<
Using the Signal mechanism (as in MacApp / TechNote 88 / SampleCode XX (I
don't remember right now) works for both C and Pascal, and you can intercept
it in one of the 8 intermediate routines if you have to do some postprocessing
if an error occurs (closing/deleting files, deallocating memory, whatever).
I use it in all my programs -- works great.
--
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(Voice)/621227(PEP)aries@rhi.hi.is (Reynir Hugason) (07/11/90)
>On an error condition I wish to immediately stop processing a large file >and break out of about 10 routines that have been calling each other and >return to my main event loop. Is there any way to do this without >passing and error flag to each of the calling routines? Here is an examplery clean way of doing it, assuming you're using Pascal 8) UNIT FileReader; INTERFACE USES ... PROCEDURE ReadFile; FUNCTION Status: INTEGER; ... and so on ... IMPLEMENTATION VAR errFlag: INTEGER; PROCEDURE ReadFile; PROCEDURE CheckError; BEGIN IF (errFlag <> noErr) THEN BEGIN { Clean-up now } EXIT(ReadFile); END; END; { Here come your procedures for reading the file } BEGIN { Initiate sequence } END; FUNCTION Status: INTEGER; BEGIN Status:=errFlag; END; END. --- Well that's it, now try to do that in C !!! 8) Mimir (aries@rhi.hi.is) - Aries Software, Inc.
keith@Apple.COM (Keith Rollin) (07/11/90)
In article <25526@cs.yale.edu> tarr-michael@CS.Yale.EDU (michael tarr) writes: > >On an error condition I wish to immediately stop processing a large file >and break out of about 10 routines that have been calling each other and >return to my main event loop. Is there any way to do this without >passing and error flag to each of the calling routines? As Blayne noted, if you are programming in C, you can use setjmp/longjmp. If you are using MacApp, then you can use the UFailure routines, CatchFailures and Success. Both of these mechanisms are subsets of the extensive Signals unit in DTS Sample Code #12. Those routines can be used from both C and Pascal, and full source code is provided. -- ------------------------------------------------------------------------------ Keith Rollin --- Apple Computer, Inc. --- Developer Technical Support INTERNET: keith@apple.com UUCP: {decwrl, hoptoad, nsc, sun, amdahl}!apple!keith "Argue for your Apple, and sure enough, it's yours" - Keith Rollin, Contusions