Hardware:

Board: NodeMCU-32S (ESP32)
Core Installation version: 1.0.4
IDE name: Arduino IDE
Computer OS: Windows 10

Description:

Attempting to use xSemaphoreCreateRecursiveMutexStatic in a sketch throws a linker error:

\Temp\arduino_build_484718\sketch\horus.ino.cpp.o:(.literal._Z5setupv+0x48): undefined reference to `xQueueCreateMutexStatic' \Temp\arduino_build_484718\sketch\horus.ino.cpp.o: In function `setup()': \Temp\arduino_build_484718\sketch/configurable.h:183: undefined reference to `xQueueCreateMutexStatic' collect2.exe: error: ld returned 1 exit status exit status 1 

The configurable.h script has no code at line 183; it's the end of the file. I checked this in the actual file in the temp folder. This appears to be a red herring. The issue is called when attempting to use the xSemaphoreCreateRecursiveMutexStatic function.

Support for this FreeRTOS feature is supposed to be enabled by setting configSUPPORT_STATIC_ALLOCATION and configUSE_RECURSIVE_MUTEXES in the build flags. I did this via platform.local.txt, along with some other flags I needed:

extras.defines=-DCONFIG_SUPPORT_STATIC_ALLOCATION=1 -DconfigSUPPORT_STATIC_ALLOCATION=1 -DconfigUSE_MUTEXES=1 -DconfigUSE_RECURSIVE_MUTEXES=1 -DconfigUSE_COUNTING_SEMAPHORES=1 build.defines={extras.defines} compiler.cpp.extra_flags={extras.defines} compiler.c.elf.extra_flags={extras.defines} compiler.c.extra_flags={extras.defines} compiler.S.extra_flags={extras.defines} 

This should enable both static and recursive semaphores, and all FreeRTOS reference states that this should work. I can see that the flags are passed as part of the compilation output.

Looking into the code here, the actual implementation of xQueueCreateMutexStatic seems to be missing. There's a forward declaration in queue.h but nothing else. The main FreeRTOS code branch includes the actual implementation.

Note that the dynamic recursive version of the function, xSemaphoreCreateRecursiveMutex, does appear to be present and working when these config flags are set. It's just the static ones that are missing.

Sketch:

#include <Arduino.h> #include <freertos/freertos.h> #include <freertos/queue.h> #include <freertos/semphr.h> SemaphoreHandle_t mutexHandle; StaticSemaphore_t mutexStatic; void setup() { mutexHandle = xSemaphoreCreateRecursiveMutexStatic(&mutexStatic); } void loop() { }