sysconfig.get_platform() could return wrong value because sys.version is truncated

Bug report

Bug description:

On Windows, sysconfig.get_platform() checks for the string amd64 (for 64 intel) in sys.version.

This is the value of sys.version for python 3.14.3 (64 bit) compiled with clang 22.1.0

>>> sys.version
'3.14.3 (main, Mar  2 2026, 14:42:29) [Clang 22.1.0 (https://github.com/llvm/llvm-project 4434dabb69916856b824f68a64b0'
>>> sysconfig.get_platform()
'win32'
>>> import platform
>>> platform.architecture()[0]
'64bit'

As visible, there is no amd64 in sys.version, because it is truncated. This causes problem when installing native package using pip because cp314-cp314-amd64 is not in the list of supported tags. Instead, the supported tags list become

Compatible tags: 48
  cp314-cp314-win32
  cp314-abi3-win32
  cp314-none-win32
  cp313-abi3-win32
  cp312-abi3-win32
  cp311-abi3-win32
  cp310-abi3-win32
  cp39-abi3-win32
  cp38-abi3-win32
  cp37-abi3-win32
  cp36-abi3-win32
  cp35-abi3-win32
  cp34-abi3-win32
  cp33-abi3-win32
  cp32-abi3-win32
  (truncated)

CPython versions tested on:

3.14

Operating systems tested on:

Windows

Linked PRs

With regard to clang, in getcompiler.c

#if defined(__clang__)
#define COMPILER "[Clang " __clang_version__ "]"

Where __clang_version__ is documented as:

__clang_version__

    Defined to a string that captures the Clang marketing version, including the Subversion tag or revision number, e.g., “1.5 (trunk 102332)”.

I think a safer implementation would be

#if defined(__clang__)
#define COMPILER "[Clang " __clang_major__ "." __clang_minor__ "." __clang_patchlevel__ "]"

This looks like an artifact of clang being untested & unsupported on Windows.

Does the full __clang_version__ include the string "amd64"?

It contains AMD64, as defined in PC/pyconfig.h, but will be truncated if __clang_version__ is long.

cpython/PC/pyconfig.h

Line 161 in 201d251

    
           #define _Py_COMPILER ("[Clang " __clang_version__ "] 64 bit (AMD64) with MSC v." _Py_STRINGIZE(_MSC_VER) " CRT]")

I think for future proofing, it is better for the sysconfig module not to depend on sys.version because it is fragile. The plaform module seems to be a better choice.

I also wouldn't be against increasing the limits in getversion.c.

sysconfig should rely on _sysconfig if it needs access to something known at compile time.

#if defined(clang)
#define COMPILER "[Clang " clang_major "." clang_minor "." clang_patchlevel "]"

I also wouldn't be against increasing the limits in getversion.c.

Both suggestions seem fine to me, too.

@char101

@char101, do you want to make a PR?

@char101, do you want to make a PR?

No, I prefer not to make a one line PR, I think the maintainer can do it faster.

I would propose this possible change though.

diff --git a/__init__.py b/__init__.py
index 2ecbff2..c612fd4 100644
--- a/__init__.py
+++ b/__init__.py
@@ -1,5 +1,6 @@
 """Access to Python's configuration information."""

+import _sysconfig
 import os
 import sys
 import threading
@@ -667,12 +668,15 @@ def get_platform():

     For other non-POSIX platforms, currently just returns :data:`sys.platform`."""
     if os.name == 'nt':
-        if 'amd64' in sys.version.lower():
+        platform_tag = _sysconfig.config_vars()['SOABI'].split('-', 1)[-1]
+        if platform_tag == 'win_amd64':
             return 'win-amd64'
-        if '(arm)' in sys.version.lower():
+        if platform_tag == 'win_arm32':
             return 'win-arm32'
-        if '(arm64)' in sys.version.lower():
+        if platform_tag == 'win_arm64':
             return 'win-arm64'
+        if platform_tag == 'win32':
+            return 'win32'
         return sys.platform

where SOABI is defined as

#ifdef PYD_PLATFORM_TAG
#  define PYD_SOABI "cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) PYD_THREADING_TAG "-" PYD_PLATFORM_TAG
#else
#  define PYD_SOABI "cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) PYD_THREADING_TAG
#endif

and the list of PYD_PLATFORM_TAG are

PC\pyconfig.h
165:#define PYD_PLATFORM_TAG "win_amd64"
169:#define PYD_PLATFORM_TAG "win_arm64"
227:#define PYD_PLATFORM_TAG "win32"    
230:#define PYD_PLATFORM_TAG "win_arm32"

pythongh-145410: Add _sysconfig.get_platform() function

sysconfig should rely on _sysconfig if it needs access to something known at compile time.

I wrote #146145 to add _sysconfig.get_platform().

gh-145410: Add _sysconfig.get_platform() function (#146145)

The Android buildbot also truncates the Clang version in sys.version: 3.15.0a7+ (heads/main-dirty:b5a27bdcf03, Mar 26 2026, 10:04:01) [Clang 18.0.4 (https://android.googlesource.com/toolchain/llvm-project d8003a456.

pythongh-145410: Add _sysconfig.get_platform() function (python#146145)

I fixed the initial issue "sysconfig.get_platform() could return wrong value because sys.version is truncated" with the change b9d4318. I close the issue.

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sysconfig.get_platform() could return wrong value because sys.version is truncated #145410

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Operating systems tested on:

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sysconfig.get_platform() could return wrong value because sys.version is truncated #145410

Description

Bug report

Bug description:

CPython versions tested on:

Operating systems tested on:

Linked PRs

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char101 commented on Mar 2, 2026

encukou commented on Mar 2, 2026

char101 commented on Mar 2, 2026

encukou commented on Mar 2, 2026

zooba commented on Mar 2, 2026

chris-eibl commented on Mar 8, 2026

encukou commented on Mar 18, 2026

char101 commented on Mar 18, 2026

char101 commented on Mar 18, 2026

vstinner commented on Mar 18, 2026

vstinner commented on Mar 26, 2026

vstinner commented on Apr 30, 2026

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