PEP 739 / build-details.json: c_api.headers does not include the pythonX.Y directory

Bug report

Bug description:

Sorry I didn't notice this while fixing #134455 but c_api.headers key contains the path to top-level system include directory, i.e.:

{
  "c_api": {
    "headers": "/usr/local/include",
    "pkgconfig_path": "/usr/local/lib/pkgconfig"
  }
}

while according to the examples in PEP 739, it should contain the path to the pythonX.Y directory:

Examples

/usr/include/python3.14
include/python3.14
etc.

CPython versions tested on:

3.14, CPython main branch

Operating systems tested on:

Linux

Linked PRs

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path

gh-134632: Fix `build-details.json` to use `INCLUDEPY` path (#134633)

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path (py…

[3.14] gh-134632: Fix `build-details.json` to use `INCLUDEPY` path (G…

This broke Android & iOS, see e.g. here:


======================================================================
FAIL: test_c_api (test.test_build_details.CPythonBuildDetailsTests.test_c_api)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/buildbot/Library/Developer/XCTestDevices/0FEBFE27-CF48-433B-AF78-485F97B08C80/data/Containers/Bundle/Application/BC1C3834-4B74-4BFC-8F77-9D59306D4B53/iOSTestbed.app/python/lib/python3.15/test/test_build_details.py", line 129, in test_c_api
    self.assertTrue(os.path.exists(os.path.join(value['headers'], 'Python.h')))
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: False is not true

FWIU this means that build-details.json was broken on these platforms in the first place. Could you give me more details, i.e. what build-details.json contains, where Python.h is installed, and how to get that path?

@freakboy3742

@freakboy3742, do you have that info?

I doubt the headers get installed after cross-compilation, but, let's wait for the experts :)

@encukou

@encukou The headers aren't installed into a running app on iOS or Android, so I think this test may need to be a skip (at least in the short term).

The headers will exist for a development environment though. However, as I flagged during the recent Core Team summit, the location isn't fixed - it essentially can't be "baked in" at time of compilation, because the install location could be wherever the user has downloaded/installed the distribution.

So - the short term fix will be a test skip; longer term, we need to determine what build-details.json should contain in a relocatable environment. I guess what we need here is the equivalent of $RPATH handling, but for the location of a relocatable Python install.

we need to determine what build-details.json should contain in a relocatable environment

iiuc, PEP-739 already allows relative paths to base_prefix, and base_prefix itself can be relative to the location of the file, so supposedly this should already be relocatable-friendly, no?

If that's the case, then it sounds like an update is required for build-details.json on iOS and Android; but at runtime, the test will always fail, so a skip is called for. Patch incoming shortly.

gh-134632: Add iOS/Android test skip for C API check for headers. (#1…

pythongh-134632: Add iOS/Android test skip for C API check for header…

[3.14] gh-134632: Add iOS/Android test skip for C API check for heade…

Actually the Android testbed does include the header files at runtime, for the benefit of the tests:

cpython/Android/testbed/app/build.gradle.kts

Lines 188 to 192 in 1c7efaf

    
           // Include files such as pyconfig.h are used by some of the tests. 
        
           into("include/$pyPlusVer") { 
        
               for (prefix in prefixes) { 
        
                   from("$prefix/include/$pyPlusVer") 
        
               }

But the runtime path will still be different to the build environment, so this will only work if relative paths are used.

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path (py…

pythongh-134632: Add iOS/Android test skip for C API check for header…

Anything left to do here?

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path (py…

pythongh-134632: Add iOS/Android test skip for C API check for header…

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path (py…

pythongh-134632: Add iOS/Android test skip for C API check for header…

Assuming not, thanks all!

pythongh-134632: Fix `build-details.json` to use `INCLUDEPY` path (py…

pythongh-134632: Add iOS/Android test skip for C API check for header…

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PEP 739 / `build-details.json`: `c_api.headers` does not include the `pythonX.Y` directory #134632

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Bug description:

CPython versions tested on:

Operating systems tested on:

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	// Include files such as pyconfig.h are used by some of the tests.
	into("include/$pyPlusVer") {
	for (prefix in prefixes) {
	from("$prefix/include/$pyPlusVer")
	}

PEP 739 / build-details.json: c_api.headers does not include the pythonX.Y directory #134632

Description

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

Activity

encukou commented on Jun 17, 2025

mgorny commented on Jun 17, 2025

encukou commented on Jun 17, 2025

encukou commented on Jun 17, 2025

freakboy3742 commented on Jun 17, 2025

itamaro commented on Jun 18, 2025

freakboy3742 commented on Jun 18, 2025

mhsmith commented on Jun 18, 2025

itamaro commented on Jun 21, 2025

hugovk commented on Aug 8, 2025

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PEP 739 / `build-details.json`: `c_api.headers` does not include the `pythonX.Y` directory #134632