missing return

[Carlos Martinez Garcia]

Hi all:

I have a piece of code similar to this:

bool MyClass::myMeth od() {
... (there is no return)
}

I have a random behaviour. It depends on if I'm debuging the code or
not. When I'm debuging it returns false, but in normal execution it
returns true.

I have no error/warnings when compile it. ¿Is it the right behaviour?

Thanks in advance

[Neelesh Bodas]

Re: missing return

Carlos Martinez Garcia wrote:[color=blue]
> Hi all:
>
> I have a piece of code similar to this:
>
> bool MyClass::myMeth od() {
> ... (there is no return)
> }[/color]

A function declared to return a value of specific type must return a
value of that type. Else it is undefined what value would be returned.
The only exception is "main" which implicitly returns 0.

[Ron Natalie]

Re: missing return

Neelesh Bodas wrote:[color=blue]
> Carlos Martinez Garcia wrote:[color=green]
>> Hi all:
>>
>> I have a piece of code similar to this:
>>
>> bool MyClass::myMeth od() {
>> ... (there is no return)
>> }[/color]
>
> A function declared to return a value of specific type must return a
> value of that type. Else it is undefined what value would be returned.
> The only exception is "main" which implicitly returns 0.
>[/color]
It's not only undefined what value might be returned, it's undefined
behavior period. While small things like bools are probably returned
via registers and just result in indeterminate values, things that the
compiler has to do more involved copy semantics for (like returning
classes) might cause the application to blow up.

[Sigmathaar]

Re: missing return

When programming a multithread application sometimes there are problems
in the synchronisation of each thread. Most of the type a bad
synchornisation may result on a missing return code or a return without
any sense. For further aid you may post the code you are working at so
we can see what the problem is.

[Sigmathaar]

Re: missing return

If you are programming a multithread application you may obtain a
return ucode sing the debug feature of your compiler because using the
debugger may give the thread the time for doing whatever it's supposed
to do.

[Howard]

Re: missing return


"Sigmathaar " <sigmathaar@gma il.com> wrote in message
news:1133193889 .257810.327160@ z14g2000cwz.goo glegroups.com.. .[color=blue]
> When programming a multithread application sometimes there are problems
> in the synchronisation of each thread. Most of the type a bad
> synchornisation may result on a missing return code or a return without
> any sense. For further aid you may post the code you are working at so
> we can see what the problem is.
>[/color]

Please quote the text of the message you're responding to.

The OP stated that there was no return (statement) for the function that was
declared to return a bool. That makes the code exhibit undefined behavior.
Threading is not relevant to the issue. If you declare a function to return
a value, then it must in fact return a value via a return statement.

-Howard

[Dervish]

Re: missing return

>I have no error/warnings when compile it
Check for compiler warning level. You should get either Error: function
does not return, or Warning: not all control paths return a value.

Other possibility - you use really ancient compiler.
[color=blue]
>but in normal execution it returns true[/color]
Better to say: it returns true with some probability. Most likely
probability = 1/256.

[izida9@gmail.com]

Re: missing return

>better to say: it returns true with some probability. Most likely probability = 1/256.

The probability is 255/256 since every value different from zero is
interpreted as "true".