Where's da bug

[Jose]

if (!(buffertask = (MsgPort *)CreateProc(Buffertaskname, 0L, buffertaskSegList, 1000L)))
  {printf("coudn't create MDBuffer/n");
   unloadseg......}
.........
.......


I'm getting Error 76 identifier expected or something with VBCC..

By the way, do I really need to cast it (eg. (MsgPort *) ) ? I was getting another error before I added that. The variable holding the result (buffertask) is declared as struct MsgPort *buffertask so I can't see what was the problem.

[Slash]

Should buffertask not be a "struct Process *" e.g.

struct Process *buffertask = NULL;

buffertask = (struct Process *)CreateNewProc(...)

That's how I create my new processes. I think CreateProc is obsolete now. Use CreateNewProc.

[Jose]

@Slash

Yes, CreatePro is obsolete but I want the code to also conditionally run on 1.3 :-)

I tried it with a struc process instead and it seems to work.
I can't really say if it works because till now VBCC was outputting the errors then crashing. Now it's just crashing after I run it so I assume there are no errors left..(don't bother asnwering I'm gonna start a new thread about my VBCC crashes.)..
 

[Jose]

I'm curious to know if it is really necessary to do the casting to struct *process when using CreatePro, or CreateNewProc...
In theory both should return that type so it shouldn't be necessary right?

[itix]

Funny but my autodocs are saying that CreateProc() returns struct MsgPort * ...

[Karlos]

Documentation error?

As far as I recall, CreateMsgPort() should return struct MsgPort*, not CreateProc().

In any event, CreateNewProc() is a bit more useful IMHO.

[Jose]

@itix

Ahh, yes!
Mine too!
So that's probably why casting is needed

[Jose]

Hmm, I checked the structures and the Process structure starts with a task structure followed by the MsgPort.
CreateProc returns the MsgPort according to the docs, so I think if I cast it fo a Process it's an error. Should be a MsgPort after all. Which brings me back to my first error(first post)!!

[itix]

Documentation error?

As far as I recall, CreateMsgPort() should return struct MsgPort*, not CreateProc().

It is funny but looks intentional. Even my good old RKRM: Includes and Autodocs is saying CreateProc() returns struct MsgPort *.

[Karlos]

Jose wrote:
Hmm, I checked the structures and the Process structure starts with a task structure followed by the MsgPort.
CreateProc returns the MsgPort according to the docs, so I think if I cast it fo a Process it's an error. Should be a MsgPort after all. Which brings me back to my first error(first post)!!

If you cast any struct X* to struct Y* and the first member struct X is not an object of type struct Y, then the cast is badly broken. You need to account for the offset of struct Y within the struct X.

I don't see that a struc MsgPort* pointer is safely castable to struct Process* unless you absolutely know for a fact that the MsgPort structure pointed to is really a member of a Process. Even then you will have to do some pointer arithmetic (or use offsetof()) to properly determing the address of the Process structure within which your MsgPort object is situated.

[Karlos]

Checked the RKMs and it does indeed return struct MsgPort* :-o

It also says that it creates a struct Process and returns it's message port.

So, I'd suggest the following dodgyness to obtain the address of the Process structure within which the MsgPort resides:

#include /* for offsetof() macro */

UBYTE* portAddr = (UBYTE*)CreateProc(.....); /* UBYTE for simple pointer arithmetic */

struct Process* process = (struct Process*)(portAddr - offsetof(struct Process, pr_MsgPort));

[itix]

if (!(buffertask = (MsgPort *)CreateProc(Buffertaskname, 0L, buffertaskSegList, 1000L)))

Your casting is wrong. It should be (struct MsgPort *), just (MsgPort *) alone is nothing and VBCC complains.

And, do you have:

struct Process *buffertask;

?

If so, it is broken because it is not returning struct Process *...

[Jose]

@itix
yes, silly me....forgot to add the type "struct"  to the cast... 8-)

[Jose]

@Karlos

Usefull. Shouldn't that be a long instead of a byte?

[Piru]

This struct MsgPort * return value is some good'ol BCPL legacy. BCPL CreateProc returns this, and so does the old dos function.

Actually BCPL considered address of Process' pr_MsgPort to be "process pointer" rather than 'struct Process *'. Processes were referenced by their pr_MsgPort address, too. Also address of various other pr_#? fields were calculated relative to pr_MsgPort, which gave some rather funky negative or positive offsets.