Analyze Rust binary bloat from monomorphization, large types, and macro expansion.
npx skills add https://github.com/fasterthanlime/.claude --skill rustc-bloat
Please help me install this Agent Skill. Skill: rustc-bloat Source: https://github.com/fasterthanlime/.claude/tree/main/skills/rustc-bloat Command: npx skills add https://github.com/fasterthanlime/.claude --skill rustc-bloat
Analyze Rust binaries to locate code bloat caused by monomorphization, large types, and macro expansion.
Build the target and run the recommended commands, saving outputs to files, then inspect /tmp/llvm-lines.txt for top bloaters.
High-intent search queries and answers about installing and using this skill.
Rust binaries grow due to monomorphization, where generic code generates separate copies for each type. Use cargo-llvm-lines to reveal which functions produce the most machine code, then inspect -Zprint-type-sizes output to find large types contributing to bloat.
Run cargo-llvm-lines on your binary to rank functions by code size, then cross-reference with -Zunpretty=expanded output to spot macro expansion contributors. Save all outputs to files and review the report identifying hotspots and optimization targets.
Yes. Monomorphization analysis requires nightly rustc flags: -Zprint-type-sizes for type detection and -Zunpretty=expanded for macro visibility. These unstable features enable the detailed inspection needed to locate code-generation bloat.
Each distinct type instantiation of a generic function triggers separate code generation—monomorphization. Macro expansion amplifies this. Profiling with cargo-llvm-lines and macro inspection reveals which generics spawn the most copies, guiding refactoring decisions.
First check for macro expansion contributors using -Zunpretty=expanded and scan llvm-lines output for duplicate function instances from monomorphization. Watch for large types flagged by -Zprint-type-sizes that multiply across instantiations.
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