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GeezerVison is showing github.com — [BOLT] specific build configs with packed rellocations segfault or miscompile with both GCC and Clang · Issue #141775 · python/cpython

[BOLT] specific build configs with packed rellocations segfault or miscompile with both GCC and Clang #141775

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[BOLT] specific build configs with packed rellocations segfault or miscompile with both GCC and Clang#141775
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corona10
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OS-linuxbuildThe build process and cross-buildThe build process and cross-buildtype-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Description

@stratakis
stratakis
opened on Nov 20, 2025
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Bug report

Bug description:

Tested on Fedora Linux 43, binutils 2.45, clang/llvm/bolt 21.1.4, gcc 15.2.1, glibc 2.42

Specific build configs when using the --enable-bolt flag fail. Found these after doing testing for #140250, which doesn't skip the computed gotos containing functions depending on the llvm version.

While this should also ideally be reported to the llvm bug tracker as well, I'm reporting it here first, towards resolving #101525

GCC:

Shared build with packed relocs:
CC=gcc LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --enable-bolt --enable-shared && make -j

On 3.14 segfaults, also with #140250
On main it passes
On main segfaults with #140250 when not skipping computed gotos functions

Shared build with LTO and packed relocs:
CC=gcc LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --with-lto --enable-bolt --enable-shared && make -j

On 3.14 bolt complains about adding sre_ucs2_match.lto_priv.0/1 to --skip-funcs
On 3.14 segfaults with #140250
On main segfaults, also with #140250

Shared build with PGO and packed relocs:
CC=gcc LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --enable-optimizations --enable-bolt --enable-shared && make -j

On 3.14 passes, also with #140250
On main segfaults, also with #140250

Shared build with LTO, PGO and packed relocs (the current Fedora built RPM):
CC=gcc LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --with-lto --enable-optimizations --enable-bolt --enable-shared && make -j

On 3.14 bolt complains about adding sre_ucs1_match.lto_priv.0/1 to --skip-funcs
On 3.14 segfaults with #140250
On main segfaults also with #140250

Clang:

clang builds might need enforcement of DWARF 4, already reported llvm/llvm-project#121554

Shared build with packed relocs:
CC=clang CXX=clang++ CFLAGS="-gdwarf-4" LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --enable-bolt --enable-shared && make -j

On 3.14 passes, also with #140250
On main passes
On main miscompiles the library with #140250 (aka without skipping computed goto functions)

Shared build with LTO and packed relocs:
CC=clang CXX=clang++ CFLAGS="-gdwarf-4" LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --with-lto --enable-bolt --enable-shared && make -j

On 3.14 segfaults, also with #140250
On main passes
On main segfaults with #140250

Shared build with PGO and packed relocs:
CC=clang CXX=clang++ CFLAGS="-gdwarf-4" LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --enable-optimizations --enable-bolt --enable-shared && make -j

On 3.14 it segfaults, also with #140250
On main it miscompiles the library, also with #140250

Shared build with LTO, PGO and packed relocs:
CC=clang CXX=clang++ CFLAGS="-gdwarf-4" LDFLAGS="-Wl,-z,pack-relative-relocs" ./configure --with-lto --enable-optimizations --enable-bolt --enable-shared && make -j

On 3.14 passes
On 3.14 segfaults with #140250
On main miscompiles the library, also with #140250

CPython versions tested on:

3.15, 3.14

Operating systems tested on:

Linux

Activity

  1. stratakis
    added
    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
    on Nov 20, 2025
  2. corona10
    self-assigned this
    on Nov 20, 2025
  3. vstinner commented on Nov 21, 2025

    @vstinner
    vstinner
    on Nov 21, 2025
    Member
    More actions

    The issue is in BOLT which miscompiles Python, no? You might report the issue to BOLT instead?

    cc @corona10

  4. picnixz
    added
    buildThe build process and cross-buildThe build process and cross-build
    OS-linux
    on Nov 21, 2025
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  • @corona10
    corona10

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OS-linuxbuildThe build process and cross-buildThe build process and cross-buildtype-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

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