Linker error in ESP-IDF framework (undefined reference) - c

Question

I am learning to write apps on ESP32 platform. When I was trying to compile my code, I got this error from linker:
undefined reference to `Serial_Init'
Where Serial_Init is a function declared in a file serial_cli.h which is in the same directory and workspace. What's more, I declared some macros there, and can use them no problem in my code, so I really don't understand where the error comes from.
Here's serial_cli.h:
#ifndef _SERIAL__H_
#define _SERIAL__H_
#include "driver/uart.h"
#define SERIAL_PORT UART_NUM_1
#define RTS_SIG_PINOUT UART_PIN_NO_CHANGE
#define CTS_SIG_PINOUT UART_PIN_NO_CHANGE
/**
* #brief This function initialises serial communication with PC
* #param uart_config_t type pointer to structure containing needed parameters
* #param int size of RX and TX buffer (in bytes)
* #param QueueHandle_t type pointer to structure containing UART queue
*/
void Serial_Init(uart_config_t*, const int, QueueHandle_t*);
#endif /* _SERIAL_H_ */
And here's serial_cli.c:
#include "serial_cli.h"
void Serial_Init(uart_config_t* uart_config, const int buffer_size, QueueHandle_t* queue)
{
ESP_ERROR_CHECK(uart_param_config(SERIAL_PORT, uart_config));
ESP_ERROR_CHECK(uart_set_pin(SERIAL_PORT, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE, RTS_SIG_PINOUT, CTS_SIG_PINOUT));
ESP_ERROR_CHECK(uart_driver_install(SERIAL_PORT, buffer_size, buffer_size, 10, queue, 0));
}
And finally, main body of the app:
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "sdkconfig.h"
#include "serial_cli.h"
#include "string.h"
void app_main(void)
{
uart_config_t uart_config = {
.baud_rate = 115200,
.data_bits = UART_DATA_8_BITS,
.parity = UART_PARITY_DISABLE,
.stop_bits = UART_STOP_BITS_1,
.flow_ctrl = UART_HW_FLOWCTRL_CTS_RTS,
.rx_flow_ctrl_thresh = 122
};
QueueHandle_t queue;
Serial_Init(&uart_config, 1024, &queue);
char* test_str = "This is a test string.\n";
while(1) {
uart_write_bytes(SERIAL_PORT, (const char*)test_str, strlen(test_str));
vTaskDelay(500);
}
}
Below I also include complete output that I get from console:
D:\Tools\ESP_IDF\examples\get-started\blink>idf.py build
Executing action: all (aliases: build)
Running ninja in directory d:\tools\esp_idf\examples\get-started\blink\build
Executing "ninja all"...
[1/8] Performing build step for 'bootloader'
ninja: no work to do.
[5/6] Linking CXX executable blink.elf
FAILED: blink.elf
cmd.exe /C "cd . && D:\Tools\ESP_IDF_container\.espressif\tools\xtensa-esp32-elf\esp-2020r3-8.4.0\xtensa-esp32-elf\bin\xtensa-esp32-elf-g++.exe -mlongcalls -Wno-frame-address #CMakeFiles\blink.elf.rsp -o blink.elf
&& cd ."
d:/tools/esp_idf_container/.espressif/tools/xtensa-esp32-elf/esp-2020r3-8.4.0/xtensa-esp32-elf/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld.exe: esp-idf/main/libmain.a(blink.c.obj):(.literal.app_main+0x8): undefined reference to `Serial_Init'
d:/tools/esp_idf_container/.espressif/tools/xtensa-esp32-elf/esp-2020r3-8.4.0/xtensa-esp32-elf/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld.exe: esp-idf/main/libmain.a(blink.c.obj): in function `app_main':
d:\tools\esp_idf\examples\get-started\blink\build/../main/blink.c:38: undefined reference to `Serial_Init'
collect2.exe: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
ninja failed with exit code 1
Thanks in advance for any feedback.

Answer 1

You need to add "serial_cli.c" to your main/CMakeLists.txt. Something like this:
idf_component_register(
SRCS
"blink.c"
"serial_cli.c"
...
See details in ESP IDF documentation