CCS C Software and Maintenance Offers
FAQFAQ   FAQForum Help   FAQOfficial CCS Support   SearchSearch  RegisterRegister 

ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

CCS does not monitor this forum on a regular basis.

Please do not post bug reports on this forum. Send them to CCS Technical Support
Problem using a function pointer

 
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion
View previous topic :: View next topic  
Author Message
bastirn



Joined: 08 Jan 2020
Posts: 17

View user's profile Send private message

Problem using a function pointer
PostPosted: Wed Jan 08, 2020 7:21 am     Reply with quote
Hello,

I'm trying to implement a shell in a PIC16F1829.
I'm stuck while i try to call a function using function pointer.
You can see a resumé of the problem.

Thanks in advance for any answer,

Best regards,
Bastien NICAUD

Code:

#include <16F1829.h>
#device PIC16F1829
#device PIC16F1829 *=16
#device ANSI
#DEVICE PASS_STRINGS=IN_RAM

#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdarg.h>
#include <stdbool.h>

#include "bnishell.h"

#DEVICE CONST=ROM

#fuses INTRC_IO         // Internal OSC

#use delay (clock=32M)
#use rs232(baud=115200, xmit=PIN_C4, rcv=PIN_C5, stream=PC)

int cmd_test(int argc, char ** argv)
{
  printf("\n\rtest\n\r");
  return SHELL_RET_SUCCESS;
}

void main(){

    char *cmd_test_argv;
    char **cmd_test_argv2;

    cmd_test_argv = 81;
    cmd_test_argv2 = &cmd_test_argv ;

    int (*toto)(int, char **);
    int zz ;

    enable_interrupts(INT_RDA);
    enable_interrupts(GLOBAL);

    //shell_init();
    //shell_register(&cmd_test, "permet de tester", "0-1", "test");

    toto = cmd_test;

    zz = cmd_test(1,cmd_test_argv2);  // Works but not what we need

    // What we want to do :
    zz = (*toto)(1,cmd_test_argv2);   // Error return : "No valid assignment made to function pointer" in the .err file
   
    printf("%d",zz);
    while (1) {
        //shell_task();
    }
 
}
Ttelmah



Joined: 11 Mar 2010
Posts: 19509

View user's profile Send private message

PostPosted: Wed Jan 08, 2020 9:25 am     Reply with quote
The problem isn't where you think it is.
It's actually the cmd_test_argv2;
Change the ** declarations to:

int (*toto)(int a, char *b[]);

and the same for the function declaration. CCS does not 'like' pointers
to pointers, but happily accepts pointers to arrays (which give exactly
the same effect).
You need to put a dummy variable name to do this (as I show)
bastirn



Joined: 08 Jan 2020
Posts: 17

View user's profile Send private message

PostPosted: Thu Jan 09, 2020 8:49 am     Reply with quote
Hello,

Thank you for you answer, now there is no more compilation error,
unfortunately it doesn't work as i want ...
Here is the code that i used :

Code:

#include <16LF1829.h>
//#device PIC16F1829
#device PIC16LF1829 *=16
#device ANSI
#DEVICE PASS_STRINGS=IN_RAM

#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdarg.h>
#include <stdbool.h>

//#include "bnishell.h"

#DEVICE CONST=ROM

#fuses INTRC_IO         // Internal OSC

#use delay (clock=32M)
#use rs232(baud=115200, xmit=PIN_C4, rcv=PIN_C5, stream=PC)

int cmd_test(int argc, char * argv[])
{
    printf("\n\rtest\n\r");
    printf("\n\r %04X \n\r",&argv);
    return 1;
}

void main(){

    delay_ms(20);

    char *cmd_test_argv;
    char *cmd_test_argv2[];

    int (*toto)(int a, char *b[]);
    int zz ;

    cmd_test_argv = 81;
    cmd_test_argv2 = &cmd_test_argv ;

    toto = cmd_test;

    //zz = cmd_test(1,cmd_test_argv2);  // Works but not what we need

    zz = (*toto)(1,cmd_test_argv2);
   
    printf("\n\r %04X \n\r",&cmd_test_argv2);
    while (1) {
    }
 
}


I should have the same adress resulting of this two printf but they are different. Any suggestion ?

Thanks in advance for any answer,
Best regards
Bastien
Ttelmah



Joined: 11 Mar 2010
Posts: 19509

View user's profile Send private message

PostPosted: Thu Jan 09, 2020 9:28 am     Reply with quote
It won't.

& means 'give the address of'. Called in the subroutine, this gives the
address of the _temporary_ variable holding the value. Not the address
of the original variable.
Display posts from previous:   
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group