How to remove unused FreeRTOS Functions from Executable

Kernel
1

Hi,

I am using the STM32F103 with Freertos and I cannot remove some unused function from my executable, it costs some extra Kbytes of Flash.

I am using the compiler options -fdata-sections -ffunction-sections -Wl,–gc-sections -Os
to remove all the unused symbols but some Freertos functions like xQueueGenericSend are still there in my executable. That happens only for the FreeRTOS functions.

I am not using Queues in my software and I also changed the FreertosConfig.h file to deactivate some functionality but the unused FreeRTOS functions are still there, in my program.

Could you explain me how can I remove this unused functions?

Your sincerely,
Nikos

2

The compiler options will place functions in separate sections. Are you then also using the linker options to remove unused sections? Note if you have configUSE_TIMERS set or if you are using semaphores then queues will be in use by the kernel.

3

ok, thank you for your reply. I am using the linker option -Wl,-gc-sections to remove the unused code. As you write, I think that the reason is that the functions are used in Semaphore.

Your sincerely,
Nikos

4

As for the linker, I added the option -Wl,--gc-sections, note that is has a double-dash before --gc. It is passed to the linker. This is the complete command:

arm-none-eabi-gcc -T my_project.ld -Xlinker
-Map="my_project.map" -mcpu=cortex-m4
-Wl,--gc-sections -mthumb ...object files...
-o my_project.elf

Another trick: can you temporarily disable compilation of the function xQueueGenericSend(), with an #if 0? The linker may then tell you which module is calling mentioned function.

5

I made the trick with the #if 0, The xTimerGenericCommand is using the xQueueGenericSend().

6

Yes, FreeRTOS uses Queue functionality for a LOT of different purposes (Queue, Semaphores, and Mutexes, and Timers use a Queue) so you normally have the basic queue code loaded, but that code also supports a lot of functionality so you don’t need other code to support it.