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Allow post scripts in library.json #4305

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maxgerhardt opened this issue Jun 6, 2022 · 6 comments
1 task done

Allow post scripts in library.json #4305

maxgerhardt opened this issue Jun 6, 2022 · 6 comments
build system docs feature ldf Library Dependency Finder


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maxgerhardt commented Jun 6, 2022

What kind of issue is this?

  • Feature Request.
    Start by telling us what problem you’re trying to solve. Often a solution
    already exists! Don’t send pull requests to implement new features without first getting our
    support. Sometimes we leave features out on purpose to keep the project small.


Operating system: Win10 x64

PlatformIO Version (platformio --version): 6.0.2

Description of problem

When writing a library, it sometimes is necessary to affect build settings of the projenv environment which is used to build the src/ folder. Such as in this example, where the inclusion of the library should cause all -fno-rtti flags to vanish.

This is only partially possible in the extraScript of a library. Using e.g. as script

global_env = DefaultEnvironment()
for e in (env, global_env):
        # key may or may not exist

leads to all -fno-rtti flags being removed in the library and framework compilation, but not for the files in src/. This is because the Arduino-ESP8266 adds them back in after it was executed, which the library build script cannot affect.

    "name": "MyLib",
    "version": "1.0.0",
    "build": {
        "unflags": "-fno-rtti"

does not work either.

Of course, build_unflags = -fno-rtti can be set in the platformio.ini to counter this, but then the user has to do an extra step when including the library.

Another use case is e.g. this library where users are being told to add extra_script to their platformio.ini that points into the library, because the library.json has no mechanism for post and pre scripts.

lib_deps =

extra_scripts =

It would be nice to specify pre: and post: in the extraScripts field / array of the library.json to allow this better without user interaction.

Steps to Reproduce

  1. Download and open
  2. Inspect lib/MyLib/
  3. Build project

Actual Results

Compilation failure, -fno-rtti not fully removed.

src\main.cpp: In function 'void setup()':
src\main.cpp:12:40: error: cannot use 'typeid' with '-fno-rtti'
   12 |     const std::type_info& ti1 = typeid(d);
      |                                        ^

Expected Results

Possibility to affect src/ compilation in extraScript, e.g. removing build flags added by later framework builder scripts.

If problems with PlatformIO Build System:

See linked project.

Additional info


@ivankravets ivankravets added ldf Library Dependency Finder build system feature help wanted and removed feature labels Jun 10, 2022
@ivankravets ivankravets added this to the 6.0.3 milestone Jun 10, 2022
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ivankravets commented Jun 16, 2022

Thanks for the report! Could you re-test with pio upgrade --dev?

Example in docs

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cziter15 commented Jun 16, 2022

Looks like projenv access feature is working as expected :)

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cziter15 commented Jun 16, 2022

After digging some more in projects it doesn't look as good. Don't really know what's wrong, but using ProcessUnFlags (-f-nortti) gives unexpected linker errors in some projects. Using board_build.unflags in platformio.ini does not bring these issues. More detais at

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cziter15 commented Jun 21, 2022

Just FYI - all problems have been resolved. Thanks!

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This doesn't work. It ignores me and builds e.g. libFS.a with no RTTI. I have no idea what is going on.

I have no control over this and typeinfo vanishes for things I need it for randomly.

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cziter15 commented Jul 6, 2024

@mathemaphysics see
I've been thinking everything was okay with this issue, but it looks like platform env is not affected by these flags.

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