Library mixup, I think

I’m running into an issue with PIO and the way I have libraries set up (all inside the lib/ folder, no external libs). The approach I’m using may not be common, but it has been working very well so far:

  • strict mode, i.e. in [env], I have lib_compat_mode = strict

  • there’s a library in lib/hall-stm32/ which only works on STM32

  • it includes a file lib/hall-stm32/library.json containing a single line:

    { "platforms": "ststm32" }

  • there’s another library in lib/hall-native/ which only works for native builds

  • it too includes a file lib/hall-native/library.json with:

    { "platforms": "native" }

  • both libraries have a header file called hall.h, with different content, as well as some other source files

So the idea is that when I include hall.h in main, or in another library, it will find just the version which matches the current build target. For main, this does indeed work well, but my impression is that when used in this way from another library (“lib/boss/” in this case, which is platform-independent and contains no library.json file), then things get mixed up. Here is the build output I see:

$ pio run -c ../../platformio.ini
Processing native (platform: native)
Verbose mode can be enabled via `-v, --verbose` option
LDF: Library Dependency Finder ->
LDF Modes: Finder ~ chain, Compatibility ~ strict
Found 2 compatible libraries
Scanning dependencies...
Dependency Graph
|-- <boss>
|   |-- <hall-native>
|-- <hall-native>
Building in release mode
Compiling .pio/build/native/src/lib/boss/boss.o
Compiling .pio/build/native/src/lib/hall-stm32/hall.o
Compiling .pio/build/native/src/lib/hall-stm32/stm32l4.o
Compiling .pio/build/native/src/main-blink.o
Compiling .pio/build/native/src/main-native.o
Compiling .pio/build/native/src/main-uart.o
Archiving .pio/build/native/lib5ae/libhall-native.a
In file included from lib/hall-stm32/hall.cpp:1:
lib/hall-stm32/hall.h:45:22: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information
            auto a = (uint32_t) &addr;
lib/hall-stm32/hall.h:40:15: error: cannot deduce return type 'auto &' for function with no return statements
        auto& at (int b) {
lib/hall-stm32/hall.h:52:15: error: cannot deduce return type 'auto &' for function with no return statements
        auto& operator[] (int b) { return at(b); }
lib/hall-stm32/hall.h:99:56: error: use of undeclared identifier 'GPIO'
        auto gpio32 (int off) const -> IOWord { return GPIO(0x400*_port+off); }

Note the “In file included from lib/hall-stm32/hall.cpp:1:” message. Somehow, a file from a library which shouldn’t be included in the native build has found its way in …

Could this be caused by the fact that main is using a generic boss which is in turn using a platform-specific hall?

For anyone interested in trying this out, these steps should suffice:

git clone
cd monty
git switch jcw
cd examples/hall/
pio run -c ../../platformio.ini -e native

I just tried this, I don’t think there are any outside dependencies.

Ehm, ignore me - PEBKAC. I had not filtered out an STM32 source file.
Everything works as intended now \o/

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