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as soon you start uncomment the me.cubed or me.timesX it crashes...

Code:
'

' An OOP-like demo.

' thanks to David of xblite 

'

TYPE OOPLIKE

  var AS LONG

  squared AS FUNCTION (this as OOPLIKE) as integer

  cubed   AS FUNCTION (this as OOPLIKE) as integer

  timesX  AS FUNCTION (this as OOPLIKE, byval x as integer) as integer

END TYPE

DECLARE FUNCTION Initialize (byval b as integer) as OOPLIKE ptr

DECLARE FUNCTION Squared (this as OOPLIKE ) as integer

DECLARE FUNCTION Cubed (this as OOPLIKE) as integer

DECLARE FUNCTION TimesX (this as OOPLIKE, byval x as integer) as integer

' start

    dim SHARED as OOPLIKE me, you

    me  = *Initialize (3)

    you = *Initialize (5)

    PRINT "================="

    PRINT "me.var      " ; me.var

    PRINT "me.squared  " ; me.squared (me)

'    PRINT "me.cubed    " ; me.cubed   (me)

'    PRINT "me.timesX   " ; me.timesX  (me, 100)

    PRINT "================="

    PRINT "you.var     " ; you.var

    PRINT "you.squared " ; you.squared (you)

'    PRINT "you.cubed   " ; you.cubed   (you)

'    PRINT "you.timesX  " ; you.timesX  (you, 100)

    PRINT "================="

    PRINT "Changing .var in me and you"

    me.var  = 6

    you.var = 7

    PRINT "================="

    PRINT "me.var      " ; me.var

    PRINT "me.squared  " ; me.squared (me)

'    PRINT "me.cubed    " ; me.cubed   (me)

'    PRINT "me.timesX   " ; me.timesX  (me, 100)

    PRINT "================="

    PRINT "you.var     " ; you.var

    PRINT "you.squared " ; you.squared (you)

'    PRINT "you.cubed   " ; you.cubed   (you)

'    PRINT "you.timesX  " ; you.timesX  (you, 100)

    PRINT "================="

        INPUT "press ENTER to exit..." ,pause

END

'

'

' ###########################

' #####  Initialize ()  #####

' ###########################

'

FUNCTION  Initialize (byval b as integer) as OOPLIKE ptr 

  dim this as OOPLIKE 

  this.var     = b

  this.squared = @Squared ()

  this.cubed   = @Cubed ()

  this.timesX  = @TimesX ()

  RETURN @this

END FUNCTION

'

'

' ########################

' #####  Squared ()  #####

' ########################

'

FUNCTION  Squared (this as OOPLIKE) as integer

  RETURN this.var * this.var

END FUNCTION

'

'

' ######################

' #####  Cubed ()  #####

' ######################

'

FUNCTION  Cubed (this as OOPLIKE) as integer

  RETURN this.var * this.var * this.var

END FUNCTION

'

'

' #######################

' #####  TimesX ()  #####

' #######################

'

FUNCTION  TimesX (this as OOPLIKE, byval x as integer) as integer

  RETURN this.var * x

END FUNCTION

just found out that if the structure is changed to

Code:
TYPE OOPLIKE

  var AS LONG

  squared AS FUNCTION (this as OOPLIKE) as integer

  cubed   AS FUNCTION (this as OOPLIKE) as integer

  timesX  AS FUNCTION (this as OOPLIKE, byval x as integer) as integer

  addspace     AS LONG  'add this for cubed function

  addmorespace AS LONG  'add this for timesX function

END TYPE

it works.

WHY?

@vic: if this is a compiler bug could you please provide a new fbc & rtl libs? (chicken/egg problem...)

Code:
FUNCTION  Initialize (byval b as integer) as OOPLIKE ptr

  dim this as OOPLIKE

  this.var     = b

  this.squared = @Squared ()

  this.cubed   = @Cubed ()

  this.timesX  = @TimesX ()

  RETURN @this

END FUNCTION

You return a pointer to a structure that no longe exists (it is deallocated when the function returns, as it is a local variable).

A solution could be to allocate it as dynamic memory:

Code:
function Initialize (byval b as integer) as OOPLike ptr

   dim this as OOPLike ptr

   this = callocate(len(OOPLike))

   this->var     = b

   this->squared = @Squared ()

   this->cubed   = @Cubed ()

   this->timesX  = @TimesX ()

   return this

end function

but then you must remember to deallocate the memory allocated later on.

Happy coding!

you could in addition to joakims suggestion write a small garbage collector that keeps track of the memory you allocated and deletes it either at program end, or during program execution time ( though this would need some thinking Smile

).

Zire has a simple "garbage collector" afair, go ask IT.

Thank you both for your reply.

Don't have time right now to try it out yet, but if it's a mem dealloc problem, than why does it work if I change the structure?

Can't wait to have more time and try it out.
Big Grin

Code:
this = callocate(len(OOPLIKE))

the compiler refuses to compile (invalid data type).

I did some more tests: as long there are the 2 additional variables in the structure, I can add more functions inside the structure (before the 2 additional variables).

Strange isn't it ...

... because if it's a matter of:

Quote:... return a pointer to a structure that no longe exists (it is deallocated when the function returns, as it is a local variable).

than it shouldn't work either way (with additional variables or not).

And this code works with no problems with xblite...

What am I missing?

As I see it, you have a pointer to deallocated memory. This is a great way to spawn hard-to-find bugs, as it'll work sometimes and other times not. I can't tell you why padding the structure makes it work (maybe v1ctor can), but it's NOT a solution to the problem. You should never return a pointer to a local variable.

I had this question awhile ago too. Vic just said do the dynamic allocation or just declare it as a Static variable.

Code:
Static this As OOPLIKE

Then the memory pointed to will change every time you call the function...

Thanks for the explanation.

I figured out why it works on xBlite:
xBlite is able to return structures, no pointer needed.

Vic, could we get structures as return argument?

BTW: Vic, don't hesitate to add your thoughts on this dilemma.

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