if you’re writing a kernel module and get the following error:

*** Warning: “symbol_name” [/path/to/module] is COMMON symbol

Than its possible that you simply forgot to mark it as static. Thanks for this fix goes to Brad Aisa from the website KernelTrap.

Bye,
Sven

Task

We have a included struct called counter and we don’t want to assign the initial values in the main function.

Solution

source.c

#include <counters.h>

struct counter_t counter = {
    .max_value = 1234,
};

int main(void)
{
    return(0);
}


Bye,
Sven

Task

We have a Makefile, we have a C file, now we want update a timestamp whenever the C file is compiled.

Solution

Makefile

CFLAGS += -D__TIMESTAMP__=\""$(shell date +%Y/%m/%d\ %H:%M:%S)"\"

source.c

#include <stdio.h>

#ifndef __TIMESTAMP__
#define __TIMESTAMP__ "NO TIMESTAMP DEFINED"
#endif /* __TIMESTAMP__ */

int main(void)
{
    printf("my tool (TS: %s)\n", __TIMESTAMP__);
    return(0);
}

Output

~$ ./source
my tool (TS: 2008/11/06 09:55:22)

Bye,
Sven