Silicon Labs EFM32 - linker fail on Thunderboard Sense 2

Development Platforms
4

Reproducable for me.

Linking .pio\build\tb_sense_12\firmware.elf
c:/users/max/.platformio/packages/toolchain-gccarmnoneeabi@1.90201.191206/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld.exe: cannot find -lrail_efr32xg12_release.ar
collect2.exe: error: ld returned 1 exit status

-Wl,–start-group -lrail_efr32xg12_release -lrail_efr32xg12_release.ar

These linker commands are the cause of the problem, the -l command shouldn’t contain the file extension and also not the lib prefix of the file.

The file C:\User\<user>\.platformio\packages\framework-mbed\targets\TARGET_Silicon_Labs\TARGET_SL_RAIL\CMakeLists.txt says

# Copyright (c) 2020 ARM Limited. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

if("EFR32_12" IN_LIST MBED_TARGET_LABELS)
    if(${MBED_TOOLCHAIN} STREQUAL "ARM")
        set(LIB_RAIL efr32-rf-driver/rail/TARGET_EFR32_12/librail_efr32xg12_release.ar)
    elseif(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
        set(LIB_RAIL efr32-rf-driver/rail/TARGET_EFR32_12/librail_efr32xg12_release.a)
    endif()
endif()

target_link_libraries(mbed-core INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/${LIB_RAIL})


target_include_directories(mbed-core
    INTERFACE
        efr32-rf-driver/rail
        efr32-rf-driver/rail/ble
        efr32-rf-driver/rail/ieee802154
)

and first of all PlatformIO or mbed-os seems to make an error here because our toolchain is GCC_ARM but still lrail_efr32xg12_release.ar for the native ARM toolchain shows up in the linker command.

I’ve tried to replace the contents of that file with

# Copyright (c) 2020 ARM Limited. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

if("EFR32_12" IN_LIST MBED_TARGET_LABELS)
    set(LIB_RAIL efr32-rf-driver/rail/TARGET_EFR32_12/librail_efr32xg12_release.a)
endif()

target_link_libraries(mbed-core INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/${LIB_RAIL})


target_include_directories(mbed-core
    INTERFACE
        efr32-rf-driver/rail
        efr32-rf-driver/rail/ble
        efr32-rf-driver/rail/ieee802154
)

but that didn’t work. By renaming the librail_efr32xg12_release.ar file to do_not_link_me.ar I found out that the build system just tries to link every single *.ar and *.a file in that folder and that it doesn’t seem to be dependent of the CMakeLists.txt logic at all.

So, after renaming the file in C:\Users\<user>\.platformio\packages\framework-mbed\targets\TARGET_Silicon_Labs\TARGET_SL_RAIL\efr32-rf-driver\rail\TARGET_EFR32_12\ from librail_efr32xg12_release.ar to librail_efr32xg12_release.ar.backup, and doing a “Clean”, “General → Miscellanenous → Rebuild IntelliSense” and “Build”, it works.

Checking size .pio\build\tb_sense_12\firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   3.7% (used 9784 bytes from 262144 bytes)
Flash: [          ]   3.7% (used 38336 bytes from 1048576 bytes)
======================= [SUCCESS] Took 4.22 seconds =======================

I’ll report this bug to Issues · platformio/platform-siliconlabsefm32 · GitHub.

Edit: Reported to Blinky mbed-os firmware does not link for tb_sense_12 board because of ARM library · Issue #4 · platformio/platform-siliconlabsefm32 · GitHub