undefined reference to `MD5Update' in arduino as component

[qt1]

The compilation of a project referencing MD5Builder fails link with undefined reference to `MD5Update'

Creating a minimal project with this error:

1. Latest ESP-IDF, install.sh and export.sh

2. Create new project using

    idf.py create-project proj1
    cd proj1
   

At this point the project compiles.

3. Add arduino-esp32 as in the docs

    mkdir -p components && \
    cd components && \
    git clone https://github.com/espressif/arduino-esp32.git arduino && \
    cd arduino && \
    git submodule update --init --recursive && \
    cd ../.. && \
    idf.py menuconfig
   

4. Rename 'proj1.c' to 'proj1.cpp' and change in 'CMakeList.txt', content from docs. At this point the project still compiles

5. Add reference to 'MD5Builder.h' like so: (based on the example in the docs)

    //file: proj1.cpp
    #include "Arduino.h"
    
    #include "MD5Builder.h"
    
    void setup(){
        Serial.begin(115200);
    
        MD5Builder hasher;
        hasher.add("hello");
        Serial.println( hasher.toString());
    }
    
    void loop(){
        Serial.println("loop");
        delay(1000);
    }
    
    extern "C" {
    void app_main(void)
    {
        setup();
        while(1)
            loop();
    }
    }
   

Now the compilation fails with linker error:

    ../components/arduino/cores/esp32/MD5Builder.cpp:37: undefined reference to `MD5Update'
    collect2: error: ld returned 1 exit status
    ninja: build stopped: subcommand failed.
    ninja failed with exit code 1

Please advise.

[atanisoft]

arduino-esp32 master (assuming that is what you are using since you didn't specify) only supports ESP-IDF v4.4 and not earlier. You state "Latest ESP-IDF" but that doesn't indicate what version you are using.

[qt1]

This happens with multiple matching versions of esp-idf and arduino-esp32.

Specifically the latest versions are:
components/arduino 399f4ec
esp-idf ddc44956bf718540d5451e17e1becf6c7dffe5b8

MD5Update is a C function that may also be available in the ROM, but I don't know.

I suspect that there is a linker setting or some flag that is needed in the the CMakeList.txt', or maybe some additional flag in some configuration file.

I would appreciate if someone that knows the system could look and help with this.

Thanks

[atanisoft]

which specific ESP32 target are you using via idf.py?

[qt1]

The target is esp32 (default). Same result when the target explicitly using idf.py set-target esp32 .

[atanisoft]

@qt1 Try disabling CONFIG_WPA_MBEDTLS_CRYPTO in your sdkconfig. It looks like when this is enabled there is no actual implementation compiled of the various MD5 functions that are used currently by MD5Builder.

The PR below fixes the issue so it doesn't depend on sdkconfig entries.

[qt1]

According to some other issues referencing MD5Update

Adding the following to esp-idf/components/esp_rom/esp32/ld/esp32.rom.ld seems to solve the problem.

    PROVIDE ( MD5Final = 0x4005db1c );
    PROVIDE ( MD5Init = 0x4005da7c );
    PROVIDE ( MD5Update = 0x4005da9c );

I is possible that theses where left out for a reason, so I m not sure if I should PR esp-idf or not..

Setting CONFIG_WPA_MBEDTLS_CRYPTO=n also solves the linker error. (I guess the first option uses ROM implementation and the other uses compiled version)

Thanks!

[atanisoft]

Those entries are intentionally omitted from the ld scripts as they used to be provided by the WPA code, as part of migrating to ESP-IDF v4.4 though this became optionally compiled based on CONFIG_WPA_MBEDTLS_CRYPTO. The PR I've created migrates to the underlying ROM APIs which are available on all targets.

[qt1]

Thanks!