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_MIPS_SIM comparison may contain undefined identifiers for _ABI #132026

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sigv opened this issue Apr 2, 2025 · 1 comment
Open

_MIPS_SIM comparison may contain undefined identifiers for _ABI #132026

sigv opened this issue Apr 2, 2025 · 1 comment
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build The build process and cross-build OS-unsupported type-bug An unexpected behavior, bug, or error

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@sigv
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sigv commented Apr 2, 2025 •
edited by bedevere-app bot
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Bug report

Bug description:

#include <Python.h>

When built on a MIPS architecture, _MIPS_SIM is used to determine architecture specifics. The value is expected to match either _ABIO32, _ABIN32 or _ABI64.

In gcc config/mips/mips.h these values are defined as compiler builtin_define inside of a switch/case. That means, mips64el and mips64 architectures know about _ABI64 but don't know about _ABIO32 and _ABIN32. In turn, when CPython tries to use them in comparison, they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be evaluated as zero, and it will not match _MIPS_SIM. However, the issues pop up when -Wundef (or, even worse, -Werror=undef) compiler flag is enabled. Then suddenly it's visible as a warning or error:

In file included from /usr/include/python3.13/Python.h:14,
                 from example.c:1:
/usr/include/python3.13/pyconfig.h:59:20: error: "_ABIO32" is not defined, evaluates to 0 [-Werror=undef]
   59 | #  if _MIPS_SIM == _ABIO32
      |                    ^~~~~~~
/usr/include/python3.13/pyconfig.h:61:22: error: "_ABIN32" is not defined, evaluates to 0 [-Werror=undef]
   61 | #  elif _MIPS_SIM == _ABIN32
      |                      ^~~~~~~

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs
@sigv sigv added the type-bug An unexpected behavior, bug, or error label Apr 2, 2025
sigv added a commit to sigv/cpython that referenced this issue Apr 2, 2025
@sigv
pythongh-132026: Ensure _MIPS_SIM has defined _ABI identifiers for co…
7492f2b 
…mparison

When built on a MIPS architecture, `_MIPS_SIM` is used to determine
architecture specifics. The value is expected to match either
`_ABIO32`, `_ABIN32` or `_ABI64`.

In `gcc` config/mips/mips.h these values are defined as compiler
`builtin_define` inside of a switch/case. That means, mips64el and
mips64 architectures know about `_ABI64` but don't know about `_ABIO32`
and `_ABIN32`. In turn, when CPython tries to use them in comparison,
they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be
evaluated as zero, and it will not match `_MIPS_SIM`. However, the
issues pop up when `-Wundef` (or, even worse, `-Werror=undef`) compiler
flag is enabled. Then suddenly it's visible as a warning or error.
@bedevere-app bedevere-app bot mentioned this issue Apr 2, 2025
Open
sigv added a commit to sigv/cpython that referenced this issue Apr 2, 2025
@sigv
pythongh-132026: Ensure _MIPS_SIM has defined _ABI identifiers for co…
d76f84e 
…mparison

When built on a MIPS architecture, `_MIPS_SIM` is used to determine
architecture specifics. The value is expected to match either
`_ABIO32`, `_ABIN32` or `_ABI64`.

In `gcc` config/mips/mips.h these values are defined as compiler
`builtin_define` inside of a switch/case. That means, mips64el and
mips64 architectures know about `_ABI64` but don't know about `_ABIO32`
and `_ABIN32`. In turn, when CPython tries to use them in comparison,
they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be
evaluated as zero, and it will not match `_MIPS_SIM`. However, the
issues pop up when `-Wundef` (or, even worse, `-Werror=undef`) compiler
flag is enabled. Then suddenly it's visible as a warning or error.
@tomasr8 tomasr8 added the build The build process and cross-build label Apr 4, 2025
@picnixz picnixz added interpreter-core (Objects, Python, Grammar, and Parser dirs) OS-unsupported and removed interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Apr 4, 2025
sigv added a commit to sigv/cpython that referenced this issue Apr 6, 2025
@sigv
pythongh-132026: Ensure _MIPS_SIM has defined _ABI identifiers for co…
5dea448 
…mparison

When built on a MIPS architecture, `_MIPS_SIM` is used to determine
architecture specifics. The value is expected to match either
`_ABIO32`, `_ABIN32` or `_ABI64`.

In `gcc` config/mips/mips.h these values are defined as compiler
`builtin_define` inside of a switch/case. That means, mips64el and
mips64 architectures know about `_ABI64` but don't know about `_ABIO32`
and `_ABIN32`. In turn, when CPython tries to use them in comparison,
they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be
evaluated as zero, and it will not match `_MIPS_SIM`. However, the
issues pop up when `-Wundef` (or, even worse, `-Werror=undef`) compiler
flag is enabled. Then suddenly it's visible as a warning or error.
sigv added a commit to sigv/cpython that referenced this issue Apr 6, 2025
@sigv
pythongh-132026: Ensure _MIPS_SIM has defined _ABI identifiers for co…
f37099c 
…mparison

When built on a MIPS architecture, `_MIPS_SIM` is used to determine
architecture specifics. The value is expected to match either
`_ABIO32`, `_ABIN32` or `_ABI64`.

In `gcc` config/mips/mips.h these values are defined as compiler
`builtin_define` inside of a switch/case. That means, mips64el and
mips64 architectures know about `_ABI64` but don't know about `_ABIO32`
and `_ABIN32`. In turn, when CPython tries to use them in comparison,
they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be
evaluated as zero, and it will not match `_MIPS_SIM`. However, the
issues pop up when `-Wundef` (or, even worse, `-Werror=undef`) compiler
flag is enabled. Then suddenly it's visible as a warning or error.
@sigv
Copy link
Author

sigv commented Apr 6, 2025

This should be added to Platform: MIPS on Unsupported platforms board.

sigv added a commit to sigv/cpython that referenced this issue Apr 6, 2025
@sigv
pythongh-132026: Ensure _MIPS_SIM has defined _ABI identifiers for co…
da82bea 
…mparison

When built on a MIPS architecture, `_MIPS_SIM` is used to determine
architecture specifics. The value is expected to match either
`_ABIO32`, `_ABIN32` or `_ABI64`.

In `gcc` config/mips/mips.h these values are defined as compiler
`builtin_define` inside of a switch/case. That means, mips64el and
mips64 architectures know about `_ABI64` but don't know about `_ABIO32`
and `_ABIN32`. In turn, when CPython tries to use them in comparison,
they may be undefined identifiers.

In default compiler behavior, the undefined identifier will be
evaluated as zero, and it will not match `_MIPS_SIM`. However, the
issues pop up when `-Wundef` (or, even worse, `-Werror=undef`) compiler
flag is enabled. Then suddenly it's visible as a warning or error.
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@sigv @tomasr8 @picnixz