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Pointer to function

 
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dev39
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Pointer to function
PostPosted: Thu Dec 31, 2009 6:50 am     Reply with quote
Hi,

I tried to create a pointer to function within a structure but it gives me error. Simple pointer to function (out side structure compiles file). Can someone let me know whats going wrong here? The compiler version I am using is 4.0

Code:


 #include <18F46K20.h>
 #use delay(clock=20000000)
 #use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
   
typedef int err_t;

typedef err_t (* _ptr_to_fn_)();

err_t test(){
return 0;
}

struct l2cap_pcb
{
_ptr_to_fn_ fn;
};

void main()
{
struct l2cap_pcb *pcb;
_ptr_to_fn_ tmp_fn;
*tmp_fn=test;
(*tmp_fn)(); //this compiles fine
(*pcb->fn)=test;
(*pcb->fn)();//this gives error
}



Thanks
dyeatman



Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK

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PostPosted: Thu Dec 31, 2009 7:42 am     Reply with quote
4.0 is not the correct compiler version.
The version number is in the format of 4.xxx (3 digits after the decimal point).
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dev39
Guest
Pointer to function- compiler version is 4.078
PostPosted: Thu Dec 31, 2009 7:53 am     Reply with quote
The compiler version is 4.081
dev39
Guest
Pointer to function- compiler version is 4.081
PostPosted: Thu Dec 31, 2009 7:54 am     Reply with quote
Sorry for the confusion in last post

The compiler version is 4.081
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Dec 31, 2009 12:28 pm     Reply with quote
Here are some threads that explain how to use function pointers in
a structure with CCS:
http://www.ccsinfo.com/forum/viewtopic.php?t=35500
http://www.ccsinfo.com/forum/viewtopic.php?t=33458
http://www.ccsinfo.com/forum/viewtopic.php?t=31637
Ttelmah
Guest
PostPosted: Thu Dec 31, 2009 3:49 pm     Reply with quote
I'm more worried about the indirection levels here.
pcb, is declared as a pointer to a structure containing a pointer to a function, but at no point is this pointer made to point to a physical structure. It could be pointing anywhere.....

Best Wishes
dev39
Guest
Thanks guys
PostPosted: Thu Dec 31, 2009 11:42 pm     Reply with quote
Thanks guys for useful responses.
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