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getting error "undefined reference to" when linking the firmware

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getting error "undefined reference to" when linking the firmware

Posted: Thu Jul 24, 2025 7:08 pm
by ivan.gerber
Hello, I'm having issues getting started with ESP-IDF programming, more specifically with CMake and building.
I come from developing using ESP-IDF with PlatformIO, after encountering some unsolvable issues when trying to use some IDF components, I tried them examples in IDF and worked very well.
Now I brought all my code from the PlatformIO project to a new ESP-IDF project, using the hello_world as template.
Some more context, I'm developing in VSCode, using the ESP-IDF extension, version of IDF: 5.4.2. Target: ESP32S3.
Here is the project folder after porting all code:
Image

Every component, except the rak3172 and the led_strip, were "libs" on the Platformio project. To add them as component I used the "+Create ESP-IDF Component" and copy the code into it.
Each CMakeLists.txt of them components is like the following:

Code: Select all

idf_component_register(SRCS "gp8211s.cpp"
                    INCLUDE_DIRS "include"
                    PRIV_REQUIRES freertos driver)

target_compile_options(${COMPONENT_LIB} PRIVATE -std=gnu++11)
Then, in the main folder I have this as CMakeLists.txt:

Code: Select all

# SRCS
set(COMPONENT_SRCS
    "main.cpp"
    "lora_gpe.cpp"
    "ble_blacklist.cpp"
    "ble_scan.cpp"
    "ble_fota.cpp"
    "energia.cpp"
    "low_power.cpp"
    "luz_ambiente.cpp"
    "ssl_db.cpp"
    "ssl_listener.cpp"
    "ssl_proceso.cpp"
    "ssl_sender.cpp"
    )
#Includes
set(COMPONENT_ADD_INCLUDEDIRS
    "include")
# Requires
list(APPEND COMPONENT_REQUIRES esp_timer)
list(APPEND COMPONENT_REQUIRES freertos)
list(APPEND COMPONENT_REQUIRES driver)
list(APPEND COMPONENT_REQUIRES spiffs)
list(APPEND COMPONENT_REQUIRES esp_common)
list(APPEND COMPONENT_REQUIRES esp_rom)
list(APPEND COMPONENT_REQUIRES esp_system)
list(APPEND COMPONENT_REQUIRES nvs_flash)
list(APPEND COMPONENT_REQUIRES esp_event)
list(APPEND COMPONENT_REQUIRES bt)
# Components, also included in the requires
list(APPEND COMPONENT_REQUIRES aes_lib)
list(APPEND COMPONENT_REQUIRES bl0942)
list(APPEND COMPONENT_REQUIRES calendario_nuclear)
list(APPEND COMPONENT_REQUIRES cJSON)
list(APPEND COMPONENT_REQUIRES configs_gpe)
list(APPEND COMPONENT_REQUIRES ESP32-RAK3172-4.2_Dev)
list(APPEND COMPONENT_REQUIRES gp8211s)
list(APPEND COMPONENT_REQUIRES gpio_gpe)
list(APPEND COMPONENT_REQUIRES gps)
list(APPEND COMPONENT_REQUIRES led_strip)
list(APPEND COMPONENT_REQUIRES opt3004)
list(APPEND COMPONENT_REQUIRES utils)

idf_component_register(SRCS ${COMPONENT_SRCS}
                        INCLUDE_DIRS ${COMPONENT_ADD_INCLUDEDIRS}
                        #requires for the project
                        REQUIRES ${COMPONENT_REQUIRES}
                        )
And the project CMakeLists.txt is:

Code: Select all

# The following lines of boilerplate have to be in your project's
# CMakeLists in this exact order for cmake to work correctly
cmake_minimum_required(VERSION 3.16)

include($ENV{IDF_PATH}/tools/cmake/project.cmake)
project(SSL-IDF)
I've read the ESP-IDF Documentation and some examples from Github, this forum, stack overflow, and others. And that got me to this moment that the firmware "compiles" but the linker fails, here is the error I get:

Code: Select all

esptool.py v4.9.0
Creating esp32s3 image...
Merged 2 ELF sections
Successfully created esp32s3 image.
Generated C:/Users/Pepe/Documents/GitHub/SSL-IDF/build/bootloader/bootloader.bin
[115/115] C:\Windows\system32\cmd.exe /C "cd /D C:\Users\Pepe\Documents\GitHub\SSL-IDF\build\bootloader\esp-idf\esptool_py && C:\Users\Pepe\.espressif\python_env\idf5.4_py3.11_env\Scripts\python.exe C:/Users/Pepe/esp/v5.4.2/esp-idf/components/partition_table/check_sizes.py --offset 0x8000 bootloader 0x0 C:/Users/Pepe/Documents/GitHub/SSL-IDF/build/bootloader/bootloader.bin"
Bootloader binary size 0x54e0 bytes. 0x2b20 bytes (34%) free.
[1203/1205] Linking CXX executable SSL-IDF.elf
FAILED: SSL-IDF.elf
C:\Windows\system32\cmd.exe /C "cd . && C:\Users\Pepe\.espressif\tools\xtensa-esp-elf\esp-14.2.0_20241119\xtensa-esp-elf\bin\xtensa-esp32s3-elf-g++.exe -mlongcalls  -fno-builtin-memcpy -fno-builtin-memset -fno-builtin-bzero -fno-builtin-stpcpy -fno-builtin-strncpy -Wl,--cref -Wl,--defsym=IDF_TARGET_ESP32S3=0 -Wl,--Map=C:/Users/Pepe/Documents/GitHub/SSL-IDF/build/SSL-IDF.map -Wl,--no-warn-rwx-segments -Wl,--orphan-handling=warn -fno-rtti -fno-lto -Wl,--gc-sections -Wl,--warn-common -T esp32s3.peripherals.ld -T esp32s3.rom.ld -T esp32s3.rom.api.ld -T esp32s3.rom.bt_funcs.ld -T esp32s3.rom.libgcc.ld -T esp32s3.rom.wdt.ld -T esp32s3.rom.version.ld -T esp32s3.rom.ble_cca.ld 
-T esp32s3.rom.ble_test.ld -T esp32s3.rom.newlib.ld -T memory.ld -T sections.ld @CMakeFiles\SSL-IDF.elf.rsp -o SSL-IDF.elf && cd ."
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(main.cpp.obj):(.literal._Z19main_generar_llavesv+0x2c): undefined reference to `AES_init_ctx_iv(AES_ctx*, unsigned char const*, unsigned char const*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(main.cpp.obj):(.literal._Z19main_generar_llavesv+0x30): undefined reference to `AES_CBC_encrypt_buffer(AES_ctx*, unsigned char*, unsigned long)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(main.cpp.obj): in function `main_generar_llaves()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/main.cpp:413:(.text._Z19main_generar_llavesv+0x68): undefined reference to `AES_init_ctx_iv(AES_ctx*, unsigned char const*, unsigned char const*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/main.cpp:416:(.text._Z19main_generar_llavesv+0x8f): undefined reference to `AES_CBC_encrypt_buffer(AES_ctx*, unsigned char*, unsigned long)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z30ssl_proceso_task_cambio_estadoPv+0x28): undefined reference to `gpio_gpe_set_pin(unsigned char, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z18ssl_proceso_init_2v+0x20): undefined reference to `gps_task(void*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z22ssl_proceso_init_pinesv+0x8): undefined reference to `gpio_gpe_init_pin(gpio_gpe_pin_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z23ssl_proceso_modo_manualP15ssl_db_config_t+0x10): undefined reference to `gpio_gpe_get_pin(unsigned char, bool*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z44ssl_proceso_cb_recalcular_alarmas_calendariov+0x20): undefined reference to `cn_sunrise(int, int, int, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj):(.literal._Z44ssl_proceso_cb_recalcular_alarmas_calendariov+0x24): undefined reference to `cn_sunset(int, int, int, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_task_cambio_estado(void*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:735:(.text._Z30ssl_proceso_task_cambio_estadoPv+0x3a): undefined reference to `gpio_gpe_set_pin(unsigned char, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_init_pines()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:527:(.text._Z22ssl_proceso_init_pinesv+0x10): undefined reference to `gpio_gpe_init_pin(gpio_gpe_pin_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_modo_manual(ssl_db_config_t*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:636:(.text._Z23ssl_proceso_modo_manualP15ssl_db_config_t+0x46): undefined reference to `gpio_gpe_get_pin(unsigned char, bool*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_modo_luz_ambiente(ssl_db_config_t*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:669:(.text._Z29ssl_proceso_modo_luz_ambienteP15ssl_db_config_t+0x42): undefined reference to `gpio_gpe_get_pin(unsigned char, bool*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_cb_recalcular_alarmas_calendario()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:947:(.text._Z44ssl_proceso_cb_recalcular_alarmas_calendariov+0x87): undefined reference to `cn_sunrise(int, int, int, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:948:(.text._Z44ssl_proceso_cb_recalcular_alarmas_calendariov+0x9b): undefined reference to `cn_sunset(int, int, int, bool)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_proceso.cpp.obj): in function `ssl_proceso_set_estado_inicial()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_proceso.cpp:716:(.text._Z30ssl_proceso_set_estado_inicialv+0x7): undefined reference to `gpio_gpe_get_pin(unsigned char, bool*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj):(.literal._Z16ssl_db_cargar_dbv+0x18): undefined reference to `configs_gpe_get_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj):(.literal._Z11ssl_db_initv+0x30): undefined reference to `configs_gpe_init()'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj):(.literal._Z11ssl_db_initv+0x34): undefined reference to `configs_gpe_set_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj): in function `ssl_db_cargar_db()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_db.cpp:1228:(.text._Z16ssl_db_cargar_dbv+0x6): undefined reference to `configs_gpe_get_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj): in function `ssl_db_init()': 
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_db.cpp:1292:(.text._Z11ssl_db_initv+0x3): undefined reference to `configs_gpe_init()'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_db.cpp:169:(.text._Z11ssl_db_initv+0x97): undefined reference to `configs_gpe_set_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj): in function `ssl_db_set_config(ssl_db_config_t*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_db.cpp:509:(.text._Z17ssl_db_set_configP15ssl_db_config_t+0x2da): undefined reference to `configs_gpe_set_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_db.cpp.obj): in function `ssl_db_set_estado_lorawan_dl(ssl_db_estado_lorawan_dl_t*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_db.cpp:900:(.text._Z28ssl_db_set_estado_lorawan_dlP26ssl_db_estado_lorawan_dl_t+0x1b0): undefined reference to `configs_gpe_set_configs(char*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(energia.cpp.obj):(.literal._Z12energia_taskPv+0x2c): undefined reference to `bl0942_init(bl0942_config_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(energia.cpp.obj):(.literal._Z12energia_taskPv+0x30): undefined reference to `bl0942_get_consumo(bl0942_data_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(energia.cpp.obj): in function `energia_task(void*)':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/energia.cpp:67:(.text._Z12energia_taskPv+0x8e): undefined reference to `bl0942_init(bl0942_config_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/energia.cpp:84:(.text._Z12energia_taskPv+0x108): undefined reference to `bl0942_get_consumo(bl0942_data_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(energia.cpp.obj): in function `energia_get_new_data()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/energia.cpp:114:(.text._Z20energia_get_new_datav+0x4c): undefined reference to `bl0942_get_consumo(bl0942_data_t*)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_listener.cpp.obj):(.literal._Z16ssl_listener_gpsv+0x14): undefined reference to `cn_init(float, float, float)'
C:/Users/Pepe/.espressif/tools/xtensa-esp-elf/esp-14.2.0_20241119/xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: esp-idf/main/libmain.a(ssl_listener.cpp.obj): in function `ssl_listener_gps()':
C:/Users/Pepe/Documents/GitHub/SSL-IDF/main/ssl_listener.cpp:199:(.text._Z16ssl_listener_gpsv+0xad): undefined reference to `cn_init(float, float, float)'
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

 *  The terminal process "C:\Users\Pepe\.espressif\tools\ninja\1.12.1\ninja.EXE" terminated with exit code: 1.
It's a lot of text, but the issue is that when files from the /main folder want to use functions from the components I made. I have no issues showing for the rak3172 and led_strip components.

Besides looking for information in forums, I tried with some IAs, but so far I couldn't resolve the linker issue.
I hope someone can give me some pointers on how to resolve this.

Re: getting error "undefined reference to" when linking the firmware

Posted: Thu Jul 24, 2025 9:08 pm
by MicroController
1. Locate the source files (.c/.cpp) where the missing functions are defined.
2. Make sure all of the above source files are listed as SRCS in their respective component CMakeLists.txt file(s).
3. Make sure the "main" component, or any other component with "undefined references", REQUIRES or PRIV_REQUIRES the component(s) which implement the missing functions.

Also,
4. If functions are defined in a C source file and are to be called from C++, make sure they are declared as extern "C".

Re: getting error "undefined reference to" when linking the firmware

Posted: Thu Jul 31, 2025 5:16 pm
by ivan.gerber
Thank you @MicroController I was missing the "extern C" on the .h of some of the components.
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