I've just tried to compile a very simple GCC/ARM-based project with FreeRTOS v9.0.0rc2. Compilation failed with the following output:

arm-none-eabi-gcc -c -mcpu=arm926ej-s -Wall -Wextra -Werror -IFreeRTOS/Source/include/ -IDemo/ -IFreeRTOS/Source/portable/GCC/ARM926EJ-S/ FreeRTOS/Source/queue.c -o obj/queue.o FreeRTOS/Source/queue.c:472:13: error: 'prvInitialiseMutex' defined but not used [-Werror=unused-function] static void prvInitialiseMutex( Queue_t *pxNewQueue ) ^ cc1: all warnings being treated as errors

(yes, the compiler is configured to treat all warnings as errors). The reason is obvious: my project is very simple and does not use mutexes at all, hence the function "prvInitialiseMutex", declared and defined in queue.c, is never called. BTW, this functiuon first appeared in this version.

I've fixed this issue by simply enclosing the declaration and definition of this function with: if ( configUSE_MUTEXES == 1 )

By doing that, my demo does build and works as expected.

I have committed this "workaround" into a side branch of my demo project, feel free to take a look at it and compare my queue.c with the original one. If you need further information, you may find my contact details in my GitHub profile.

Looking forward to hear about the official solution of this issue.

Good feedback, thanks. Our testing tends to use comprehensive configurations so warnings generated by simpler configurations can be missed. It is always the aim to have no warnings.