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Superfluous dialect symbol in inline assembly #157250

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Superfluous dialect symbol in inline assembly#157250
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interpreter-core(Objects, Python, Grammar, and Parser dirs)type-bugAn unexpected behavior, bug, or error

Description

@fuhsnn
fuhsnn
opened on Sep 10, 2026

Bug report

Bug description:

This inline assembly block has an extra { at the start that is likely a typo:

cpython/Include/internal/pycore_pystate.h

Line 327 in f715d25

__asm__("{movq %%rsp, %0" : "=r" (result));

In GCC style inline assembly syntax, { initiates an dialect selector block [1] and this case forms an unfinished section of that.
It being silently accepted by current GCC/Clang is likely just them being permissive.

[1] https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html#Multiple-assembler-dialects-in-asm-templates

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

Activity

  1. fuhsnn
    added
    type-bugAn unexpected behavior, bug, or error
    on Sep 10, 2026
  2. picnixz
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    on Sep 10, 2026

  3. encukou commented on Oct 15, 2026

    @encukou
    encukou
    on Oct 15, 2026
    Member

    Sorry for missing this issue/PR.
    The line was changed in #158167 to:

        __asm__ ("{movq %%rsp, %0|mov %0, rsp}" : "=r" (result));

    Do we need a GCC #ifdef for this?

  4. fuhsnn commented on Oct 15, 2026

    @fuhsnn
    fuhsnn
    on Oct 15, 2026
    ContributorAuthor

    Thanks for informing!

    Do we need a GCC #ifdef for this?

    Not for slimcc, I just implemented support for these (including the permissive behavior)

  5. encukou
    closed this as completedon Oct 16, 2026
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