Dependancy issues with Preproccessor directives

[Awbmilne]

Configuration

Operating system: Windows 10

PlatformIO Version: v5.0.4

Description of problem

When building a project with preprocessor directives that optionally include certain libraries, Libraries that are NOT needed/wanted are included when compiling. This creates issues when you have two libraries that define the same symbols with different values.

#if SOMETHING
  #include <A_library.h>
#else
  #include <B_library.h>
#endif

Steps to Reproduce

This issue reared its head when compiling Networking code for a Teensy 4.1. Compiling the below file set should recreate the issue:

main.cpp

#include <Arduino.h>

#ifdef __IMXRT1062__ //Processor ID for Teensy 4 and Teensy 4.1
    #include "NativeEthernet.h"
#else
    #include "Ethernet.h" // Comment this line out to see the expected result
#endif

uint8_t MAC[6] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress IP = {192,168,0,100};

void setup(){
    Serial.begin(9600);
    while(!Serial);
    Ethernet.begin(MAC, IP);

    // Hardware checks from Teensy Examples
    // Check for Ethernet hardware present
    if (Ethernet.hardwareStatus() == EthernetNoHardware) {
        Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
        while (true) {
        delay(1); // do nothing, no point running without Ethernet hardware
        }
    }
    Serial.println("No Issues!");
}

void loop(){

}

platformio.ini

[env:default]
platform = teensy
board = teensy41
framework = arduino

Actual Results

Expected Results

Additional info

While this is generally not an issue, In specific cases like this one, This creates an issue where the wrong version of Ethernet.hardwareStatus() is used (along with the rest of the ethernet functions), meaning the Ethernet connection doesnt work. This is best demonstrated by the Serial output of the above script.

Expected

Actual

Solution

In order to eliminate this issue, preprocessor directives need to be taken into account either during the dependency search or during the compiling.

[liquiddandruff]

See https://docs.platformio.org/en/latest/librarymanager/ldf.html?highlight=dependency#c-c-preprocessor-conditional-syntax

In short, try the chain+ mode:

[env:myenv]
lib_ldf_mode = chain+

If that doesn't work try defining explicitly:

[env:myenv]
lib_ldf_mode = chain+
build_flags = -D __IMXRT1062__ 

[ivankravets]

Thanks, @liquiddandruff for the solution!

[Awbmilne]

Really appreciate it @liquiddandruff ! 🥂