[question] Cannot use cpython as a downstream dependency

[Todiq]

What is your question?

Hello,

I am not really sure in which repo to create this ticket, since I don't know if it comes from a recipe's misuse or a conan client misuse (or something else).

I have a library alpha and a library beta that depends on it. Both need to link with boost python. As boost python is not set to automatically gather cpython, I would like to get it through the conanfile, rather than using the system one.

Here is an example : https://github.com/Todiq/test_conan

You juste have to run python build.py. I only tested it on Windows.


While the build of alpha passes, it fails on beta:

CMake Warning (dev) at C:/Program Files/Microsoft Visual Studio/2022/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.28/Modules/FindPackageHandleStandardArgs.cmake:438 (message):
  The package name passed to `find_package_handle_standard_args` (Python3)
  does not match the name of the calling package (Python).  This can lead to
  problems in calling code that expects `find_package` result variables
  (e.g., `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  C:/Program Files/Microsoft Visual Studio/2022/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.28/Modules/FindPython/Support.cmake:3867 (find_package_handle_standard_args)
  C:/Program Files/Microsoft Visual Studio/2022/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.28/Modules/FindPython3.cmake:545 (include)
  D:/conan/p/cpythaac989ed1ef63/p/bin/libs/cmake/use_conan_python.cmake:14 (include)
  build/windows-msvc/generators/FindPython.cmake:38 (include)
  CMakeLists.txt:24 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

-- Found Python3: D:/conan/p/cpythaac989ed1ef63/p/bin/libs/cmake/../../python.exe (found version "3.9.19") found components: Interpreter
-- Configuring done (1.4s)
CMake Error at betaimpl/CMakeLists.txt:10 (target_link_libraries):
  Target "betaimpl" links to:

    Python::Python

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.



-- Generating done (0.0s)
CMake Generate step failed.  Build files cannot be regenerated correctly.

ERROR: conanfile.py (test_beta/1.0): Error in build() method, line 52
        cmake.configure()
        ConanException: Error 1 while executing

Replacing find_package(Python COMPONENTS Development QUIET) with find_package(Python3 COMPONENTS Development QUIET) in beta's cmake removes the initial warning, but does not fix the issue (no warning in alpha though).


In beta's recipe, I tried using self.requires("cpython/3.9.19", override=True) instead of the regular self.requires("cpython/3.9.19") as well, but that would not fix the issue either.


Am I missing something? Thanks in advance for your help!

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[memsharded]

Thanks for your report @Todiq

I am trying to reproduce with your repo code, but my build is failing at an earlier stage, while building "boost":

boost/1.85.0: RUN: "C:/Users/memsharded/Envs/conan2_310/Scripts/python.exe" -c "from __future__ import print_function; import sys; print('{}.{}'.format(sys.version_info[0], sys.version_info[1]))"

boost/1.85.0: WARN: Boost component 'numpy' is missing libraries. Try building boost with '-o boost:without_numpy'. (Option is not guaranteed to exist)
ERROR: boost/1.85.0: Error in package_info() method, line 1997
        raise ConanException(f"These libraries were expected to be built, but were not built: {non_built}")
        ConanException: These libraries were expected to be built, but were not built: {'boost_numpy310'}

No idea why this is happening, I'd need to investigate

[Todiq]

@memsharded,

I am using python 3.9.13 on my side, but I don’t think that will differ much from your version

Boost (recipe?) expects to have numpy installed (of course, I know you’re not blind).

The only workaround I found so far for this is to install it in the (virtual) environment. But here’s the catch: I never made it work with a version > 1.26.4. Meaning that starting from numpy version 2.0.0 and upwards, I would get the same error as yours (if my memory is correct). Could you please try with 1.26.4?

[Todiq]

You error looks like the one mentionned here: #11241

[Todiq]

@memsharded @valgur

Do you think it might be related to #16952 ?

[Todiq]

Hi @memsharded,

Would you mind having a look again when you have some time please? I know you must be very busy. Thanks in advance.