Re: Callback interface

Thanks to Leon's tireless efforts, here is an add in fix that should
work on any of the recent SwiftForth's

WINDOWS-INTERFACE OPEN-PACKAGE
PUBLIC
: CB: ( xt n -- ) \ Usage: xt n CB: <name>
    CREATE
    RUNCB ,CALL DUP
    [+ASM] CELLS # RET NOP [-ASM]
    0= IF [+ASM] NOP NOP [-ASM] THEN \ Fix bug in 3.0.6 & 7
    ( xt) , ;
END-PACKAGE

I'm still working on other issues with the GLUT interface, and I'll
report when I have something working.

DaR

On Jan 16, 2007, at 9:26 AM, Dennis Ruffer wrote:

> I just found this issue last night, while struggling with the OpenGL
> interface. It does not solve all the issues, but I do not know when
> I will get my test case finished. So, I should let you all know what
> I found, in case it might be useful to others and maybe, someone
> knows a "better" solution.
>
> The callback logic in Src/IDE/Win32/Callback.f presumes that the
> function's xt is located 4 bytes after the return address inside
> RUNCB:
>
> 4 [EDX] EBX MOV \ get xt for tos
>
> ' CALLBACK >CODE CALL \ and run the word...
>
> Normally, this is correctly accomplished by the defining word:
>
> : CB: ( xt n -- ) \ Usage: xt n CB: <name>
> CREATE
> RUNCB ,CALL
> [+ASM] CELLS # RET NOP [-ASM]
> ( xt) , ;
>
> However, this is dependent on what RET assembles:
>
> : RET ( n # | -- )
> DUP IMM? IF DROP ?DUP IF C2 C,(A) W,(A) \ imm16
> EXIT THEN THEN C3 C,(A) ;
>
> If you are really sharp, you see the problem, but I don't really want
> to say how long I've been chasing it.
>
> The problem is with a callback that does not have any parameters. In
> that case, the RET assembles a C3 and the RUNCB logic calls garbage.
>
> I solved the problem by commenting out the inner conditional within
> RET and my OpenGL tests no longer crash as soon as I call the
> glutMainLoop. The callback assigned to glutIdleFunc is called
> immediately, with no parameters, and crashes before it executes any
> of the user's code. ;(
>
> This solution requires a remake of the SF executable, so for those
> who do not have the full system, an update or some other solution is
> required.
>
> DaR
>
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Received on Tue Jan 16 2007 - 21:08:26 PST