When I say "goto", my parrot says "Spaghetti Code"

RandyBuchholz

Mention "goto" to many programmers and they'll say, "Never use them, they lead to spaghetti code." It's a conditioned response. It seems to be a definition - "Dad, what's for dinner?" - "We're having `goto`." - "Again?". Ask them to explain why it is so bad, and you'll likely get a blank stare, or they just chant "spaghetti, spaghetti, …" Of course, a misused `goto` can lead to spaghetti code, but a (misused) [`any reserved word`] can lead to [`some bad thing`]. Have we developed an irrational fear of `goto` born out of ancient coding dogma? Or is `goto` inherently and absolutely evil? :) Update: As suggested by englebart, I'm adding why I asked this question. It came out of a recent discussion. I was reviewing some code someone showed me (they didn't write it) that had a `goto` in it. He said the code was Spaghetti Code. When I asked why, he said because it had a `goto`. I asked why that made it spaghetti, and all he could come up with was that he was taught that. I asked about a few other "programming truths", and had much the same response. This is good, that is bad, but I don't really know why. I started thinking about how for some things, aspects of programming have become more faith than science.

den2k88

It creates functions which are strictly monolithic. It's not bad but it create impediments in further expansions or refactorizations of the function that uses it. Goto to code outside the function containing it is problematic for the compilers, breaks modularity in C code as much as global variables do, and is completely undoable in OOP due to context changes. All in all it may be a good solution but ultimately not worth the delayed troubles if not under very constrained circumstances.

GCS d-- s-/++ a- C++++ U+++ P- L+@ E-- W++ N+ o+ K- w+++ O? M-- V? PS+ PE- Y+ PGP t+ 5? X R+++ tv-- b+(+++) DI+++ D++ G e++ h--- ++>+++ y+++* Weapons extension: ma- k++ F+2 X

Lost User

Looking to some MSDN examples, I never saw goto, I only saw things like this (also a kind of goto): .... while(true) { if (!Method_1()) break; ... if (!Method_N()) break; ... } ...

It does not solve my Problem, but it answers my question

RandyBuchholz

There are `goto`s in the source code for C# in places.

RandyBuchholz

I would say your examples are good examples of misuse, and not problems with `goto` itself. I don't use `goto` myself, except in rare cases to short-circuit a function.

Lost User

Hi,

RandyBuchholz wrote:

It's a conditioned response.

That's exactly what it is. A few years ago I had to use some goto statements in a device driver written in C where the push/pop function prolog/epilog[^] was causing a performance reduction of between 30% - 40%. I could not find anything that matched the speed of the goto statement and left it in the production code. High-performance code is almost always ugly.

RandyBuchholz wrote:

Or is goto inherently and absolutely evil?

I would say that you do not need a goto statement 99.999% of the time. But I have used it at least ONE time in the past two decades where I feel it was necessary. Best Wishes, -David Delaune

CPallini

I do not use goto in C++ programs while I use it in C ones. I do abuse of gotos in assembly code.

CodeWraith

RandyBuchholz wrote:

Have we developed an irrational fear of

Speak for yourself. :-) Just look what I'm working on right now. Every opcode that starts with B is a branch (= goto). :-)

; =========================================================================================
; BIOS Command selection
;
; Parameters:
; ---
;
; Returns:
; ---
; =========================================================================================

BIOS_Command: LDI hi(TxtEnterCommand)
STXD
LDI lo(TxtEnterCommand)
STXD
SEP R4
dw WriteLine

CMD_Repeat: LDI 00FFH ; get RS232 input, max. timeout
STXD
SEP R4
dw RS232InSoftware

				IRX								; timeout?				
				LDX
				BZ   CMD\_Skip

				STXD							; echo input
				STXD
				SEP	 R4
				dw   RS232Out

				IRX
				LDX
				SDI  006EH						; test input = n	
				BZ   CMD\_Exit
				
				LDX
				SDI  0079H				
				BNZ  CMD\_Repeat

				LDI  hi(TxtNewLine)				; announce BIOS CMD
				STXD
				LDI  lo(TxtNewLine)
				STXD
				SEP  R4
				dw   WriteLine

				LDI  hi(TxtNewLine)
				STXD
				LDI  lo(TxtNewLine)
				STXD
				SEP  R4
				dw   WriteLine

				LDI  hi(TxtCmdTitle)
				STXD
				LDI  lo(TxtCmdTitle)
				STXD
				SEP  R4
				dw   WriteLine

CMD_Prompt: LDI hi(TxtCmdPrompt) ; output the prompt
STXD
LDI lo(TxtCmdPrompt)
STXD
SEP R4
dw WriteLine

				LDI  00H						; get RS232 input, no timeout
				STXD
				SEP  R4
				dw   RS232InSoftware
				LDI  TRUE
				PLO  RF

				IRX								; echo input								
				LDX
				STXD
				STXD
				SEP	 R4
				dw   RS232Out
				
				IRX				
				LDX								; test input = x
				SDI  0078H				
				BZ   CMD\_Exit

				LDX								; test input = X
				SDI  0058H				
				BZ   CMD\_Exit

				LDX								; test input = h
				SDI  0068H				
				BZ   CMD\_Help

				LDX								; test input = H
				SDI  0048H				
				BZ   CMD\_Help

CMD_Invalid: LDI hi(TxtCmdInvalid) ; error message (invalid command)
STXD
LDI lo(TxtCmdInvalid)
STXD
SEP R4
dw WriteLine
BR CMD_Prompt

CMD_Help: LDI hi(TxtCmdHelp) ; help text
STXD
LDI lo(TxtCmdHelp)
STXD
SEP R4
dw WriteLine

				LDI  hi(TxtCmdHelp1)
				STXD
				LDI  lo(TxtCmdHelp1)
				STXD
				SEP  R4
				dw   WriteLine
				BR

Marc Clifton

Sacrilege! You will goto hell for such thoughts! Oh wait. Even hell has been refactored: while (true) burnInHellForever(); ;)

Latest Article - Building a Prototype Web-Based Diagramming Tool with SVG and Javascript Learning to code with python is like learning to swim with those little arm floaties. It gives you undeserved confidence and will eventually drown you. - DangerBunny Artificial intelligence is the only remedy for natural stupidity. - CDP1802

RandyBuchholz

I have no fears! :-D My education is EE, and I still see registers (68xx architecture) in my head no matter what language I'm programming in. I don't actually see the code that way, it's just kind of a background image. It's amazing how many developers don't know that the only branching a CPU has is a `goto`.

Gary Wheeler

I've not used the goto keyword in any of my C/C++/C# code over the last 20 years or so. I routinely use break (goto's more civilized brother, as it were) to exit for loops early. I do this in cases where expressing the iteration as a for loop is more appropriate for the general case, and the break handles the exceptions. I don't tend to use continue nearly as much in similar situations; I'm not sure why. I dislike when code uses exceptions as an exotic form of iteration/flow control. My least favorite mechanism would have to be setjmp()/longjmp(), which is a very old C runtime library mechanism that fortunately doesn't see a lot of use today.

Software Zen: delete this;

RandyBuchholz

Not:

Quote:

while (true) burnInHellForever();

`while (false) burnInHellForever();` "true" believers go to heaven! ;P

CodeWraith

Even one as unconventional as this one here. :-)

I have lived with several Zen masters - all of them were cats. His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

Rick York

I think it depends on the context. In C it's not so bad and I can think of a few notable examples where it is used. One instance I found rather humorous and posted in a coding 'hall of fame' page we used to have here, is in the default procedure of Windows v3.0 and the label used was "IcantBelieveIactuallyUsedAgoto." The source code of it was published in an old book by Peter Norton on windows programming. On the other hand, I think using goto in C++ is a really bad idea. Since objects are automatically deleted when they fall out of scope, a goto could result in memory leaks if not used very carefully. As far as I am concerned this opinion is not based on fear nor is it irrational. YMMV.

GuyThiebaut

Back in 1988 when I went to university to study computer science we were taught that we were never to use goto except in one particular circumstance with COBOL. We were strictly taught structured programming and in the first year had 2 hours of computer time each week. Most of our work was done on paper. Fast forward to now and I am quite happy to use a return statement in code which in essence is a goto. I think in principle it's good to learn the rules of structured programming to know when it is ok to break those rules.

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

Nathan Minier

For several years programmers have had OOAD and OOP pounded into their heads, and goto is an inherently structured code construct. If you use goto in an object oriented program, you _are_ creating spaghetti code, which is why that particular reflex exists.

"There are three kinds of lies: lies, damned lies and statistics." - Benjamin Disraeli

Maximilien

I don't have an existentialism issue with goto. It can have its uses, very limited, but can be useful. We have a few in some of our older legacy C code. None in the new C++ code.

I'd rather be phishing!

OriginalGriff

It's not an irrational fear: it's a sensible precaution. goto is a "shortcut" for lazy lecturers and lazy students - it positively encourages poor quality code and bad habits. That doesn't mean it shouldn't be used, just that you have to understand why you aren't using it before you should be allowed to use it. It has its place (try doing assembly code, or time critical embedded C / C++ without it) but generally speaking it's a bad idea in "modern" languages which have rich flow control constructs and a set of good practices which should mean that it isn't that necessary. For example, I've been coding in C# for nine years now, and not once have I needed to use a goto, nor have I had to "fudge round" not using one. It annoys me when it's taught early because the idiot running the course can't be bothered to teach a while, for, or foreach loop to beginners. Because once you start using a hammer, every problem looks like a nail...

Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

Lost User

RandyBuchholz wrote:

Have we developed an irrational fear of goto born out of ancient coding dogma? Or is goto inherently and absolutely evil? :)

Are we asking annoying questions, just for the sake of asking? Jumping to a label was once an improvement ovr jumping to a specific linenumber. You are doing as if using a "GOTO 40" still has a place in modern C# coding. It doesn't. No, it's not a dogma; you don't have to believe me and can feel free to GOTO anywhere in your code - it will be your problem, not mine :)

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^] "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

RandyBuchholz

Quote:

Are we asking annoying questions, just for the sake of asking?

No, not just for the sake of asking, just for the sake of annoying. :) Also to see how many mind readers would jump on me for using them - even though I didn't say I used them. :) And don't, except in rare, low-level performance cases. It came out of a recent discussion. I was reviewing some code someone showed me (they didn't write it) that had a `goto` in it. He said the code was Spaghetti Code. When I asked why, he said because it had a `goto`. I asked why that made it spaghetti, and all he could come up with was that he was taught that. I asked about a few other "programming truths", and had much the same response. This is good, that is bad, but I don't really know why. I started thinking about how for some things, aspects of programming have become more faith than science.