malloc

[Antony]

Hi,
pls let me know whether the release 3.190 can solve the problem of the
function Malloc that is not working in a larger program.
Thanks

[Haplo]

The CCS change log ( http://www.ccsinfo.com/versions.shtml ) doesn't mention anything. What exactly is the problem are you talking about?

[ABS]

I had problems with malloc always returning null.

Now, I moved the #include <stdlibm.h> statement to immediately follow #pragma USE DYNAMIC_MEMORY which follows the device statements at the top of the program.

#include <18F258.h>
...Device statements...
#pragma USE DYNAMIC_MEMORY
#include <stdlibm.h>

This got malloc to work where I expected it. I have not thoroughly tested the new code.

[Jeprox]

I gave up using malloc with ver 3.173.
It doesn't work, even using the #pragma USE DYNAMIC_MEMORY and #include <stdlibm.h>
If anyone can tell me it works pls post a simple code so I can try it.

[Antony]

The following code doesn't allocate indipendents parts of memory for the
strings but overwrites totally or partially the locations of memory, loosing
the real content of the strings.
It's a bug of the release 3.177 or is there an error in the code?

#include <18F452.H>
#pragma USE DYNAMIC_MEMORY
#include
#include
#ZERO_RAM

unsigned char *stringa1, *stringa2, *stringa3;

void main()
{
while(1)
{
stringa1 = malloc(stringa1);
strcpy(stringa1, "STRINGA1");

stringa2 = malloc(stringa2);
strcpy(stringa2, "STRINGA2");

stringa3 = malloc(stringa3);
strcpy(stringa3, "STRINGA3");
}
return;
}

[abs]

[Guest]

Thanks,
but also the follow code doesn't work.


#include <18F452.H>
#pragma USE DYNAMIC_MEMORY
#include <stdlibm.h>
#include <string.h>
#ZERO_RAM

unsigned char *stringa1, *stringa2, *stringa3;

void main()
{
free(stringa1);
stringa1 = NULL;
free(stringa2);
stringa2 = NULL;
free(stringa3);
stringa3 = NULL;

stringa1 = malloc(stringa1);
strcpy(stringa1, "STRINGA1");

stringa2 = malloc(stringa2);
strcpy(stringa2, "STRINGA2");

stringa3 = malloc(stringa3);
strcpy(stringa3, "STRINGA3");
while(1)
{
}
return;
}

[ckielstra]

I don't know for the CCS compiler, but in other compilers you are NEVER allowed to call free() with an uninitialized pointer!

In this example code your calls to free() are pointless because you haven't called malloc() yet.

Furthermore your calls to malloc() are wrong. You need to specify how many bytes of storage you want to be returned:

[Guest]

sorry,
i have forgotten a piece of code,
i have to allocate a piece of RAM that is function of the length of stringa.
Thanks

#include <18F452.H>
#pragma USE DYNAMIC_MEMORY
#include <stdlibm.h>
#include <string.h>
#ZERO_RAM

unsigned char *stringa1, *stringa2, *stringa3;
int num;

void main()
{
strcpy(stringa1, "STRINGA1");
num = strlen(stringa1);
stringa1 = malloc(num);

strcpy(stringa1, "STRINGA2");
num = strlen(stringa2);
stringa2 = malloc(num);

strcpy(stringa1, "STRINGA3");
num = strlen(stringa3);
stringa3 = malloc(num);

while(1)
{
}
return;
}

[ckielstra]

Computers always do what you tell them to do, this is (often) not equal to what you want them to do.......

[Guest]

Hi,
i have changed the code (is been the first version of code), but it doesn't work.
Test the follow code!


#include <18F452.H>
#pragma USE DYNAMIC_MEMORY
#include <stdlibm.h>
#include <string.h>
#ZERO_RAM

unsigned char *stringa1, *stringa2, *stringa3;
int num;

void main()
{
num = strlen("STRINGA1");
stringa1 = malloc(num);
strcpy(stringa1, "STRINGA1");

num = strlen("STRINGA2");
stringa2 = malloc(num);
strcpy(stringa2, "STRINGA2");

num = strlen("STRINGA3");
stringa3 = malloc(num);
strcpy(stringa3, "STRINGA3");

while(1)
{
}
return;
}

[Charlie U]

I am not very familiar with the malloc() function, but there may be a problem with the basic use of strlen(). According to K&R, strlen(s) returns the length of the string EXCLUDING the terminating null. Therefore, num will be the number of characters in your string, not the total amount of memory required for the string. If you allocate that much memory for the string, and then copy the string to that location, won't the treminating null be outside of the allocated memory? It seems that you should be using something like the following:

[Haplo]

Just a quick note: You'll need to allocate one byte more than the length of your string to cater for the terminating NULL character.
Change your code to:

[Guest]

OK!
Test the follow code: it doesn't work!


#include <18F452.H>
#pragma USE DYNAMIC_MEMORY
#include <stdlibm.h>
#include <string.h>
#ZERO_RAM

unsigned char *stringa1, *stringa2, *stringa3;
int num;


void main()
{
num = strlen("STRINGA1")+1;
stringa1 = malloc(num);
strcpy(stringa1, "STRINGA1");

num = strlen("STRINGA2")+1;
stringa2 = malloc(num);
strcpy(stringa2, "STRINGA2");

num = strlen("STRINGA3")+1;
stringa3 = malloc(num);
strcpy(stringa3, "STRINGA3");

while(1)
{
}
return;
}

[Darren Rook]

stdlibm.h is open. If you're convinced there is a bug, why don't you look at stdlibm.h and figure out whats wrong?