Gosub.02bas error

[José Roca]

This example fails with an error: "Unidentified instruction when".

Code: [Select]

'% filename "t.exe"
'uses rtl64


function f()
  int a=42
  int b

  'gosub g
  gosub g when a>0
  print b
  return
  '
  g:
  b=a/2
  ret
  '
end function

f


[Aurel]

Jose
as you know GOSUB is keyword so there is no WHEN

gosub to g... ?
g - should be SUBROUTINE or FUNCTION... ok 

[José Roca]

The program is not mine. It is one of the examples that comes with the compiler and I'm just pointing that it fails.

> gosub to g... ?
> g - should be SUBROUTINE or FUNCTION... ok 

No, it should be a label.

[Charles Pegge]

Will be fixed.

if, when, while, until are  currently supported for goto and gosub.

[José Roca]

> if, when, while, until are  currently supported for goto and gosub.

What do you mean?

[Charles Pegge]

In this context, when and while are the same as if.

Until is the same as if not ...

This is experimental syntax

[Aurel]

Well ... i don't know that we have WHEN in o2 
and i never use gosub to jump to label only to call function
also i never use until too

[José Roca]

Do you use Gosub  to call a Function? How?

[JRS]

SB allows doing a GOSUB within a FUNCTION/SUB to a LABEL but using GOSUB/GOTO to reference a function sounds non-BASIC to me.

[Charles Pegge]

Yes, it is possible to use gosub to call a function that has no parameters, though you would not normally do this.

[Aurel]

Yes ..like this:

'gosub calls
declare sub hey()

gosub hey

sub hey
print "Hey Oxygen"
return
end sub

Of course I use it very rare

[José Roca]

Doesn't look worthwile.

[JRS]

Doesn't look worthwile.

+1

BASIC is diluted enough. We don't need core syntax doing tricks.

[Mike Lobanovsky]

I'm almost sure that's kind of an (almost) unnoticed side effect left over from the early stages of syntax experimentation; a transition from gosub to genuine subprocedures. Used to have some such in FBSL BASIC myself.

[Charles Pegge]

But There is a problem in 64bit mode. You will lose 16byte stack pointer alignment when making a gosub to a procedure. Therefore gosubs should only be used to call a subroutine, or piece of asm.

PS:

I can remove this vulnerability to stack-pointer misalignment by adding one instruction to the procedure's internal prolog. It rounds the stack pointer down to the nearest 16-byte boundary:

and rsp, -16

This will cost about half a nanosecond per call