Global Variable Usage

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1

Hello,

I am wondering how does RIOT handles the use of global variables across multiple files. I need access an array across multiple system files (RIOT/sys/net/gnrc/). If I include the custom header file, I get “multiple definition error”. May I request for a solution to this kind of issue.

I tried looking up how RIOT was internally accessing such a variable. I was unable to find it. Please point out any such usage, if possible.

Additional details can be found at https://github.com/RIOT-OS/RIOT/issues/10186 (please look at the last comment by me(npcode15)). I am asking this question here as it might not be relevant for that issue.

Thank you.

Regards,

Navneet Pandey

2

Hi Navneet,

As far as I am aware the only decent way to do this in C is to only reference a global variable using "extern" in your header file, and then define it in a different file that is only built once (often a .c file). See for instance, "saul_reg" in "sys/include/saul_reg.h" and "sys/saul_reg/saul_reg.c"

Sincerely, Matthew Blue

3

Thank you.