[krehel]

• ELFShim::Metadata built a PatchELF::Patcher, and so an elftools ELFFile that parses every header through BinData, to read a few fields from the program headers and the dynamic section. Read them with String#unpack instead: the linkage check, relocation and brew bottle read them for every ELF file in a keg.
• Return exactly what patchelf.rb returned, string encodings included, and leave anything unusual, such as a truncated file, to patchelf.rb as before.
• Reading metadata no longer loads elftools, BinData and patchelf.rb.

---

• Have you followed our Contributing guidelines?
• Have you checked for other open Pull Requests for the same change?
• Have you explained what your changes do? Performance claims (e.g. "this is faster") must include brew benchmark results.
• Have you explained why you'd like these changes included, not just what they do?
• For bug fixes, have you given step-by-step brew commands to reproduce the bug?
• Have you written new tests (excluding integration tests)? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) locally?

---

• I did not use AI/LLM to create this PR, or I disclosed the tool/model below and reviewed its output; I did not attribute commits to AI and will answer maintainer questions and review comments myself without AI/LLM.

---

Opus 5.5 xhigh with manual review and testing. The new reader was compared with main's on 3,363 ELF files (arm64 and x86_64 bottles, system libraries and 32-bit and big-endian builds) and on 19,929 truncated or overwritten copies of 1,418 of them: every value, string encoding and exception matched.

Details

Fedora 44 aarch64 VM, hyperfine -N with brew benchmark's environment, bottles cached.

brew linkage util-linux ($(brew --cache)/linkage.json removed before each run, 20 runs)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
main a687be2	351.5 ± 32.1	318.3	449.2	1.55 ± 0.19
branch	226.3 ± 18.0	207.5	264.4	1.00

brew linkage perl ($(brew --cache)/linkage.json removed before each run, 20 runs)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
main a687be2	277.5 ± 29.8	248.6	360.8	1.36 ± 0.15
branch	204.5 ± 4.3	196.1	214.9	1.00

brew install util-linux (one pour, dependencies installed, 10 runs)

Command	Mean [s]	Min [s]	Max [s]	Relative
main a687be2	2.211 ± 0.021	2.199	2.268	1.08 ± 0.02
branch	2.042 ± 0.022	2.013	2.070	1.00

brew install python@3.15 (one pour, dependencies installed, 10 runs)

Command	Mean [s]	Min [s]	Max [s]	Relative
main a687be2	2.506 ± 0.029	2.467	2.549	1.05 ± 0.02
branch	2.398 ± 0.041	2.352	2.484	1.00

brew install wget (one pour, dependencies installed, 20 runs)

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
main a687be2	969.7 ± 12.6	954.9	998.6	1.04 ± 0.02
branch	935.8 ± 9.4	924.6	961.0	1.00

brew install jq wget git tmux htop python3 (39 bottles poured, warm cache, 10 runs)

Command	Mean [s]	Min [s]	Max [s]	Relative
main a687be2	22.227 ± 0.150	22.046	22.551	1.02 ± 0.01
branch	21.762 ± 0.120	21.583	21.965	1.00

Reading the metadata of 3,354 ELF files through ELFShim alone takes 2,295 ms on main and 182 ms on the branch (12.6 ± 0.6×). Pours gain less because relocation still rewrites each file through patchelf.rb.

[coderabbitai]

No actionable comments were generated in the recent review.

Recent review info

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Commits

Reviewing files that changed from the base of the PR and between 07e4b86 and 032cb6d.

Files selected for processing: 5

• Library/Homebrew/os/linux/elf.rb
• Library/Homebrew/test/os/linux/pathname_spec.rb
• Library/Homebrew/test/support/fixtures/elf/exe_s390x
• Library/Homebrew/test/support/fixtures/elf/libx_arm32.so.2
• Library/Homebrew/test/support/fixtures/elf/static_no_phdrs

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

Summary

Summary by CodeRabbit

• Improvements
  • ELF metadata can now be read directly across 32-bit and 64-bit files in either byte order, including key library and executable details.
  • Unsupported or incomplete files continue to use the existing fallback reader, while malformed files are handled without returning partial metadata.
  • Files without program headers are now recognised as non-dynamic.

ELFShim::Metadata now reads ELF metadata directly from program headers and the dynamic section. It supports 32-bit and 64-bit files in either byte order, and uses patchelf for unsupported or incomplete input. Specs cover direct reading, fallback cases and files without program headers.

Changes: ELF metadata reading

Layer / File(s)	Summary
Direct ELF parsing Library/Homebrew/os/linux/elf.rb	Adds format constants, a fields structure and a direct reader for ELF headers, program headers and dynamic-section data. Bounded readers handle fields and null-terminated strings.
Fallback selection and validation Library/Homebrew/os/linux/elf.rb, Library/Homebrew/test/os/linux/pathname_spec.rb	Metadata initialisation selects fields from the direct reader or patchelf. PIE and NODEFLIB checks use local flag constants. Specs cover fallback selection, 32-bit little-endian and 64-bit big-endian files, and files without program headers.

Merge Risk: Minimal · up to 032cb

No actionable issue remains from this review; the PR is ready for normal merge checks.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly summarises the main change: reading ELF metadata without loading elftools.
Description check		The description directly explains the implementation, motivation, compatibility requirements, tests, and benchmark results for the ELF metadata reader.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[MikeMcQuaid]

Nice, thanks!