python / python/cpython

BOLT-WARNING: specifying numeric value "1" for option -icf is deprecated

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build type-bug
Dominant language
Python
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Description

Bug report

Bug description:

Building 3.14.5 with gcc 15.2 and --enable-bolt produces this warning:

    default: BOLT-WARNING: specifying numeric value "1" for option -icf is deprecated

This line in configure.ac hard codes -icf=1 in BOLT_APPLY_FLAGS:

https://github.com/python/cpython/blob/54a5fd4126df74f7b84d1f8a6a36ef79803f66f9/configure.ac#L2258

This issue mentions ICF behavior: https://github.com/python/cpython/pull/134642

Build environment: Ubuntu 26.04 LTS, gcc 15.2.0, configure with:

./configure --enable-optimizations --with-lto --enable-bolt --enable-safety --enable-slower-safety --with-system-expat CXX=/usr/bin/g++ CFLAGS="-flto=auto" LDFLAGS="-flto=auto"
CPython versions tested on:

3.14

Operating systems tested on:

Linux

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with configure.ac around line 2258, where BOLT_APPLY_FLAGS hard-codes the deprecated -icf value. Reproduce the warning with the provided --enable-bolt configure command and inspect the related ICF behavior described in pull request 134642. Done means the Linux build no longer emits this BOLT-WARNING.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
build-system
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
76/100

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