How to use malloc( ) and free( ) in PICC?

[kerden]

pic malloc

I have writed a simple program like this:
/* ******************************* */
#include<stdlib.h>

void main(void)
{
unsigned char *ptr;

ptr = (unsigned char *) malloc(sizeof(unsigned char));
free(ptr);
}
/* ***************************** */
This just used to test how to use malloc() and free() in PICC.But after compiled,some error message appear:
Error[000] : undefined symbols:
Error[000] : _free (D:\MPLAB IDE\PICproject\Test\test.obj)
Error[000] : _malloc (D:\MPLAB IDE\PICproject\Test\test.obj)

I have doubt in why these error message appear.How to do dynamic memory's program such use malloc() and free() in PICC?
Best regards,

 

[elec4fun]

malloc pic

Hi,

To use malloc() and free() you need to include stdlib.h

Regards.

 

[kerden]

pic18f malloc

Hi,

To use malloc() and free() you need to include stdlib.h

Regards.

yes !
i have included stdlib.h

 

[elec4fun]

pic18 malloc

Ho sorry, I don't know why, my browser didn't show me the <stdlib.h>....
I've tested your code on my mplab with picc18 and it's work. May be you have a problem with your library installation....I don't think picc and picc18 are different when using free() and malloc().

 

[revolution1983]

mcc18 malloc

I think it has no heap space in pic mircocontroller.
but malloc() and free() are used to control heap in personal computer.

I think the reason is from PIC compiler

 

[kerden]

hi-tech malloc

Ho sorry, I don't know why, my browser didn't show me the <stdlib.h>....
I've tested your code on my mplab with picc18 and it's work. May be you have a problem with your library installation....I don't think picc and picc18 are different when using free() and malloc().

thank you very much.
i ve also tested my code with picc and picc18,but i doesn't work.are you picc18 is a demo? where have you downloaded?

 

[elec4fun]

malloc et pic

My picc18 it's not a demo....but I think your code could work with a demo version. Try to put stdlib.h in the directory of your simple program and put #include "stdlib.h" instead.

 

[kerden]

malloc() mcc18

My picc18 it's not a demo....but I think your code could work with a demo version. Try to put stdlib.h in the directory of your simple program and put #include "stdlib.h" instead.

i have copy the stdlib.h under the project file.but it doesn't work;
some error as follow


The target "D:\picc\PIC18\fgh.obj" is already up to date.
Executing: "C:\HTSOFT\PIC18\BIN\PICC18.EXE" -E"2.lde" "D:\picc\PIC18\fgh.obj" -M"2.map" -O"2.cof" -O"2.hex" -Q -MPLAB -18F248
Error[000] : undefined symbols:
Error[000] : _free (D:\picc\PIC18\fgh.obj)
Error[000] : _malloc (D:\picc\PIC18\fgh.obj)
Error[000] D:\picc\PIC18\fgh.obj 17 : Fixup overflow in expression (loc 0x20 (0x1C+4), size 1, value 0x100)
Error[000] D:\picc\PIC18\fgh.obj 17 : Fixup overflow in expression (loc 0x22 (0x1C+6), size 1, value 0x101)
Error[000] fgh.rlf 24 : Fixup overflow in expression (loc 0x1 (0x1+0), size 1, value 0x100)
Error[000] fgh.rlf 28 : Fixup overflow in expression (loc 0x1 (0x1+0), size 1, value 0x101)
BUILD FAILED: Fri Mar 24 18:59:03 2006

 

[btbass]

malloc mcc18

If you look at the application notes on Microchip website you will find some c code for dynamic allocation of Ram using homebrewed malloc and free. You have to modify the linker file to get some heap memory from which to allocate and free ram.
I am using my own version of it for a linked list and it works just fine.
I am using Microchips Mcc18 compiler for the 18 series. I much prefer it to Hi-Tech.
Hi-Tech is ok for the low end 16 series