Very strange bug hard to understand (.b types related ? )

[Psychophanta]

Well, i have reduced the code to the maximum in order to post here the possible bug. Get it here

Please refer to the arrowed commented comments in the lines and try to understand, because i can't
Explanation would be welcomed

[va!n]

i see your problem... atm i am a bit to tired but i think it could be a problem with the macro MyFlipBuffers (modify registers or something!?)

[Psychophanta]

...but i think it could be a problem with the macro MyFlipBuffers (modify registers or something!?)

That is what i believed, but ... no possible

[Dr. Dri]

i don't understand your problem but with these lines the program doesn't crash anymore forme

Code: Select all

      If StartDrawing(ScreenOutput())
        DrawText(200,300,"md = "+Str(md)+"; PMODE = "+Str(PMODE),$eeeeee,0)
        StopDrawing()
      EndIf

Dri

[Psychophanta]

Hi Dr. Dri.
The problem has nothing to do with that.
Those lines can be erased from the snippet, those lines are not significative coz they are just to watch the variable PMODE at real time.

The problem is that the arrow must remain up or down, but the behaviour is wrong because it tend to remain up, even you move the mouse to set it to down.
As the source comment says, if the type of PMODE variable is set to .w instead to .b, then the program behaviour works as expected. Do you see it?

[Dr. Dri]

I didn't have this problem
the only thing is that it crashed without the "if"

Dri

[Psychophanta]

I didn't have this problem

??? Strange! Here it happens

the only thing is that it crashed without the "if"

? Strange again! here it doesn't crash!!
Notice: i use (PB4.01 with betas)

[manu]

I had a look at your code.
The problem is that in your inline assembly line

Code: Select all

  !fistp dword[v_MustDelay];<-  MustDelay=DispPeriod-(checkpoint2-checkpoint1)/SysFreq.

you store 32bits at the address of your variable MustDelay which is only 8bits wide, which is why your variable PCODE (also 8bits) gets overwritten. When you make PCODE larger, it probably gets stored somewhere else so it isn't overwritten and the code seems to be fine.
Change MustDelay.b to MustDelay.l and everything works as expected.

manu

[Psychophanta]

I had a look at your code.
The problem is that in your inline assembly line

Code: Select all

  !fistp dword[v_MustDelay];<-  MustDelay=DispPeriod-(checkpoint2-checkpoint1)/SysFreq.

you store 32bits at the address of your variable MustDelay which is only 8bits wide, which is why your variable PCODE (also 8bits) gets overwritten. When you make PCODE larger, it probably gets stored somewhere else so it isn't overwritten and the code seems to be fine.
Change MustDelay.b to MustDelay.l and everything works as expected.

manu

manu, my hero! big thanks, you have discover a bug in the snippet
And yes, it seems the only bug is made by the programmer in this case.
Please mods, may you delete this thread? or move it to another place?