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GeezerVison is showing github.com — gh-149202: Don't use -fno-omit-frame-pointer on ppc64le by vstinner · Pull Request #149485 · python/cpython

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@vstinner

@vstinner vstinner commented May 7, 2026 •
edited by bedevere-app Bot
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The power ABI specification requires that compilers maintain a back chain by default, so unwinding already works without a dedicated frame pointer. Don't use -fno-omit-frame-pointer on ppc64le.

  • Issue: Implement PEP 831 – Frame Pointers Everywhere: Enabling System-Level Observability for Python #149202

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@vstinner
pythongh-149202: Don't use -fno-omit-frame-pointer on ppc64le
ea140bb 
The power ABI specification requires that compilers maintain a back
chain by default, so unwinding already works without a dedicated
frame pointer. Don't use -fno-omit-frame-pointer on ppc64le.
@vstinner
vstinner requested review from corona10 and erlend-aasland as code owners May 7, 2026 09:10
@vstinner vstinner added the skip news label May 7, 2026
@vstinner
vstinner requested review from AA-Turner and emmatyping as code owners May 7, 2026 09:10
@bedevere-app bedevere-app Bot mentioned this pull request May 7, 2026
Implement PEP 831 – Frame Pointers Everywhere: Enabling System-Level Observability for Python #149202
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@bedevere-app bedevere-app Bot added the awaiting core review label May 7, 2026
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read-the-docs-community Bot commented May 7, 2026

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Documentation build overview

📚 cpython-previews | 🛠️ Build #32580775 | 📁 Comparing ea140bb against main (612140e)

  🔍 Preview build  

1 file changed
± using/configure.html
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@vstinner

vstinner commented May 7, 2026

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This PR implements @stratakis' suggestions: #149409 (comment). Extract:

Adding however -fno-omit-frame-pointer forces the compiler to reserve r31 for it adding extra overhead with no benefits.

cc @stratakis @encukou @pablogsal @Fidget-Spinner @savannahostrowski
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@vstinner vstinner mentioned this pull request May 7, 2026
gh-149202: Fix frame pointer unwinding on ppc64le and armv7/clang #149409
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@vstinner

vstinner commented May 7, 2026

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I tested this change manually on Linux ppc64le:

  • ./configure (gcc -O3): OPT=-DNDEBUG -g -O3 -Wall in Makefile
  • ./configure --with-pydebug (gcc -Og): OPT=-g -Og -Wall in Makefile

test_frame_pointer_unwind pass successfully.
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pablogsal
pablogsal approved these changes May 7, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels May 7, 2026
@pablogsal

pablogsal commented May 7, 2026

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Thanks Victor!
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@vstinner

vstinner commented May 7, 2026

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!buildbot PPC64LE
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@bedevere-bot

bedevere-bot commented May 7, 2026

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🤖 New build scheduled with the buildbot fleet by @vstinner for commit ea140bb 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F149485%2Fmerge

The command will test the builders whose names match following regular expression: PPC64LE

The builders matched are:

  • PPC64LE Fedora Rawhide Clang PR
  • PPC64LE RHEL8 Refleaks PR
  • PPC64LE RHEL8 LTO + PGO PR
  • PPC64LE Fedora Stable Clang PR
  • PPC64LE Fedora Rawhide NoGIL refleaks PR
  • PPC64LE Fedora Rawhide PR
  • PPC64LE CentOS9 LTO PR
  • PPC64LE Fedora Rawhide Clang Installed PR
  • PPC64LE Fedora Stable Refleaks PR
  • PPC64LE Fedora Rawhide LTO PR
  • PPC64LE Fedora Stable PR
  • PPC64LE Fedora Stable LTO + PGO PR
  • PPC64LE CentOS9 LTO + PGO PR
  • PPC64LE Fedora Stable LTO PR
  • PPC64LE Fedora Rawhide NoGIL PR
  • PPC64LE Fedora Rawhide Refleaks PR
  • PPC64LE Fedora Stable Clang Installed PR
  • PPC64LE Fedora Rawhide LTO + PGO PR
  • PPC64LE CentOS9 PR
  • PPC64LE RHEL8 LTO PR
  • PPC64LE RHEL8 PR
  • PPC64LE CentOS9 Refleaks PR
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@vstinner
vstinner merged commit b3cfd36 into python:main May 7, 2026
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@vstinner
vstinner deleted the ppc64le branch May 7, 2026 09:47
@bedevere-app bedevere-app Bot removed the awaiting merge label May 7, 2026
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Reviewers

@pablogsal pablogsal pablogsal approved these changes
@erlend-aasland erlend-aasland Awaiting requested review from erlend-aasland erlend-aasland is a code owner
@corona10 corona10 Awaiting requested review from corona10 corona10 is a code owner
@AA-Turner AA-Turner Awaiting requested review from AA-Turner AA-Turner is a code owner
@emmatyping emmatyping Awaiting requested review from emmatyping emmatyping is a code owner

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@vstinner @pablogsal @bedevere-bot
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