[sdcc-devel] [ sdcc-Bugs-818483 ] Passing parameters when calling a function throuh a pointer

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Bugs item #818483, was opened at 2003-10-06 09:49
Message generated for change (Comment added) made by bernhardheld
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Category: msc51(8051) target
Group: non bugs
Status: Closed
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Bernhard Held (bernhardheld)
Summary: Passing parameters when calling a function throuh a pointer

Initial Comment:
The code:




// File eg.c


int (* pFunction)(int); // Pointer to a function




extern int g;


void Function(int i)    // The function to be called


{


        g = g + i;


}




void Example(void)


{


        // The asignement of the function pointer


        pFunction = Function;




        // The call that can be compiled but... what


        // about the parameter the function waits for?


        pFunction;




        // The desired call to a function through a


        // pointer that cannot be compiled


        pFunction(1);   // Line 20


}




// End of file




Cannot be compiled with the command 'sdcc -c eg.c' 
because of 'too many parameters error' at line 20.




I tried the 2.3.5 version. Snapshots Oct 3 2003 and Apr 
21 2003.




My email address: Joa...@ya...




I hope this report can help to improve the already 
excellent sdcc. Thank you,


Joan Martinez






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>Comment By: Bernhard Held (bernhardheld)
Date: 2003-10-07 09:29

Message:
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SDCC doesn't build a call tree. The overlay feature in SDCC is 
much simpler than e.g. in Keil's compiler. It's well explained in 
our Fine manual:
http://sdcc.sourceforge.net/doc/sdccman.html/node26.html

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Comment By: Nobody/Anonymous (nobody)
Date: 2003-10-07 08:55

Message:
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I was assuming that the compiler could not build up the
function call tree. (Looses track which function is (or may 
be) called by the function pointer).
So if there are two functions f and fp (which would both use  
overlayed variables) and f calls fp by a function
pointer then fp could change variables which belong to f?

Frieder


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Comment By: Bernhard Held (bernhardheld)
Date: 2003-10-06 21:59

Message:
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I don't know of any reason, why functions, which are called via 
pointers, should be used with nooverlay. 

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Comment By: Frieder Ferlemann (frief)
Date: 2003-10-06 11:57

Message:
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... and those not having a parameter should be used with the
pragma nooverlay (when they do not have the reentrant keyword).
 
Is that correct?


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Comment By: Bernhard Held (bernhardheld)
Date: 2003-10-06 10:11

Message:
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user_id=203539

Functions, which take parameters and are called via pointer 
must be reentrant:

int (* pFunction)(int) reentrant;
void Function(int i) reentrant
{
  g = g + i;
}


http://sdcc.sourceforge.net/doc/sdccman.html/node64.html
(*pFunction)(1);

----------------------------------------------------------------------

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