Cannot link project using msgpack-c library

[marco711]

Hello, I'm using the msgpack-c library in my project. I've been working with the msgpack_pack_str_body and msgpack_pack_int16 functions without problem. Now I want to use the msgpack_unpack_next and msgpack_object_print functions as in the "Simple program with a loop" but I get the following compilation error:

[5/7] Linking CXX executable mqtt_tcp.elf
FAILED: mqtt_tcp.elf 
.
.
.
b/gcc/riscv32-esp-elf/8.4.0/../../../../riscv32-esp-elf/bin/ld: esp-idf/main/libmain.a(message_pack_functions.c.obj): in function `messagepack_encoding':
/home/esp/IoTlift/mqtt-tcp/build/../main/message_pack_functions.c:77: undefined reference to `msgpack_unpack_next'
/home/.espressif/tools/riscv32-esp-elf/esp-2021r2-patch3-8.4.0/riscv32-esp-elf/bin/../lib/gcc/riscv32-esp-elf/8.4.0/../../../../riscv32-esp-elf/bin/ld: /home/esp/IoTlift/mqtt-tcp/build/../main/message_pack_functions.c:81: undefined reference to `msgpack_object_print'
/home/.espressif/tools/riscv32-esp-elf/esp-2021r2-patch3-8.4.0/riscv32-esp-elf/bin/../lib/gcc/riscv32-esp-elf/8.4.0/../../../../riscv32-esp-elf/bin/ld: esp-idf/main/libmain.a(message_pack_functions.c.obj): in function `msgpack_unpacked_destroy':
/home/esp/IoTlift/mqtt-tcp/build/../msgpack-c/msgpack-c-c_master/include/msgpack/unpack.h:260: undefined reference to `msgpack_zone_free'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
ninja failed with exit code 1

Nevertheless, the library is included in the project and msgpack_zone_free is in "zone.h" file which is included in "unpack.h" file. How can I solve this problem?

[redboltz]

msgpack_pack_str_body is an inline function. https://github.com/msgpack/msgpack-c/blob/c3df1bb26ebdd01d618ecca7ae2d6b4e37d5abd7/cmake/pack_template.h.in#L782-L785

msgpack_zone_free is not an inline function. https://github.com/msgpack/msgpack-c/blob/c3df1bb26ebdd01d618ecca7ae2d6b4e37d5abd7/src/zone.c#L217-L222

So you need to link the library libmsgpackc.a.

[marco711]

Thank you. How do I link this library?

[redboltz]

See your compiler/linker manual. Usualy -lmsgpackc.

[marco711]

Hello, I'm using ESP-IDF which uses CMake and Ninja build. I've been reviewing the *cmake and CMakeLists.txt files in order to try to link the library libmsgpackc.a but it is not clear for me how to do the linking.

[redboltz]

Here are example source files and CMakeLists.txt. The following line might help you. https://github.com/msgpack/msgpack-c/blob/c_master/example/CMakeLists.txt#L22

You can also try https://github.com/msgpack/msgpack-c/tree/c_master#install-from-git-repository instruction.

[marco711]

Thank you. I have tried to reinstall the library with the []((https://github.com/msgpack/msgpack-c/tree/c_master#install-from-git-repository) instruction and the linking still fails. Then, I've tried by modifying the CMakeLists.txt file in the msgpack-c folder but I still get the linking error at the same line. Finally, I've tried by modifying the CMakeLists.txt file in the folder containing the "app_main.c" file and I the linker cannot find the "nvs_flash.h" file.

[redboltz]

It seems that the issue is caused by your code not msgpack-c. I cant help you any more.

[marco711]

OK, thanks for your time. I will recreate the project from scratch.

[marco711]

Hello, I have downloaded the MQTT-TCP example and I have downloaded and installed the msgpack-c library in the folder "tcp". Then, I have included the library (#include <msgpack.h>) and added some of its functions in the main function:

void app_main(void)
{
    ESP_LOGI(TAG, "[APP] Startup..");
    ESP_LOGI(TAG, "[APP] Free memory: %d bytes", esp_get_free_heap_size());
    ESP_LOGI(TAG, "[APP] IDF version: %s", esp_get_idf_version());

    esp_log_level_set("*", ESP_LOG_INFO);
    esp_log_level_set("MQTT_CLIENT", ESP_LOG_VERBOSE);
    esp_log_level_set("MQTT_EXAMPLE", ESP_LOG_VERBOSE);
    esp_log_level_set("TRANSPORT_BASE", ESP_LOG_VERBOSE);
    esp_log_level_set("esp-tls", ESP_LOG_VERBOSE);
    esp_log_level_set("TRANSPORT", ESP_LOG_VERBOSE);
    esp_log_level_set("OUTBOX", ESP_LOG_VERBOSE);

    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    mqtt_app_start();
    
/* Messagepack code. */
	msgpack_sbuffer *buffer = msgpack_sbuffer_new();
	msgpack_packer *pk = msgpack_packer_new(buffer, msgpack_sbuffer_write);

        for(int j = 0; j<23; j++) {
           /* NB: the buffer needs to be cleared on each iteration */
           msgpack_sbuffer_clear(buffer);

           /* serializes ["Hello", "MessagePack"]. */
           msgpack_pack_array(pk, 3);
           msgpack_pack_bin(pk, 5);
           msgpack_pack_bin_body(pk, "Hello", 5);
           msgpack_pack_bin(pk, 11);
           msgpack_pack_bin_body(pk, "MessagePack", 11);
           msgpack_pack_int(pk, j);

           /* deserializes it. */
           msgpack_unpacked msg;
           msgpack_unpacked_init(&msg);
           msgpack_unpack_return ret = msgpack_unpack_next(&msg, buffer->data, buffer->size, NULL);

           /* prints the deserialized object. */
           msgpack_object obj = msg.data;
           msgpack_object_print(stdout, obj);  /*=> ["Hello", "MessagePack"] */
           msgpack_unpacked_destroy(&msg);
           puts("");
        }
        /* cleaning */
        msgpack_sbuffer_free(buffer);
        msgpack_packer_free(pk);	

}

The build fails with the same error (undefined reference to ...). Did I install the msgpack library in the wrong folder? Moreover, it is not clear for me how to modify the CMakeLists.txt files. Any help will be appreciated.

[vk015]

I have also build the project and tried to run the example programs, but getting the undefined reference error while linking..