How to use malloc in nRF9160?

[Yusuke]

I can' initialize malloc. Any help?

I implement code like bellow.

<main.c>
..
char *Cmd_crlf;
..

void main(void)
{
    ..
    printk("here1\r\n");
    Cmd_crlf = (char *) malloc(10);
	if (Cmd_crlf == NULL) {
		printk("malloc is null\r\n");
	}
	..
}

<prj.conf>
CONFIG_HEAP_MEM_POOL_SIZE=1024

<output>

here1
malloc is null

[Martin Lesund]

Hello Yusuke,

I would recommend to check out the documentation.

You can use k_malloc();

Here is an example on how to allocate memory:

char *mem_ptr;

mem_ptr = k_malloc(200);
if (mem_ptr != NULL)) {
    memset(mem_ptr, 0, 200);
    ...
} else {
    printf("Memory not allocated");
}

[TBP]

Hey,

I tried using k_malloc and got a linking error:

 undefined reference to `k_malloc`

Is there something else I need to in order to use k_malloc?

Thanks,

Tal

[lavande]

Hi , Martin, 

Where is the definition of 'k_malloc'?

[KevinThompson-SR]

I'm having same exact issue... any resolution or suggestions?

[drunot]

Have you remembered to allocate heap space? E.g. set 'CONFIG_HEAP_MEM_POOL_SIZE' in 'prj.conf' to a non zero value?

[robbsadler]

Even now in 2025 in SDK 2.8, I was getting 

undefined reference to `k_malloc`

The above suggestion was the solution. It would be helpful if this rule requiring heap space be allocated was mentioned in the compiler error instead of an undefined reference.