Gcc

This one walks you through GCC flag selection for different build modes: debug with `-g -Og`, release with `-O2` or `-O3 -march=native`, size-optimized with `-Os`, and sanitizer builds. It covers LTO and PGO workflows step by step, warning flag discipline with `-Wall -Wextra`, and a triage table for common errors like undefined references and ABI mismatches. The optimization decision tree is practical, especially the note that `-O3` can regress performance due to instruction cache pressure. If you've ever second-guessed whether to enable `-flto` or wondered why `-Ofast` broke your floating point math, this gives you the exact invocations and explains the tradeoffs without the usual compiler flag folklore.

skills.sh installs: 741
GitHub stars: 279
last updated: Aug 21, 2026

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Install

$ npx -y skills add mohitmishra786/low-level-dev-skills --skill gcc --agent claude-code

Installs into .claude/skills of the current project.

Files

GCC

Purpose

Guide agents through GCC invocation: flag selection, build modes, warning triage, PGO, LTO, and common error patterns. Assume the project uses GNU Make, CMake, or a shell script.

Triggers

"What flags should I use for a release build?"
"GCC is giving me a warning/error I don't understand"
"How do I enable LTO / PGO with GCC?"
"How do I compile with -fsanitize?"
"My binary is too large / too slow"
Undefined reference errors, ABI mismatch, missing symbols

Workflow

1. Choose a build mode

Goal	Recommended flags
Debug	`-g -O0 -Wall -Wextra`
Debug + debuggable optimisation	`-g -Og -Wall -Wextra`
Release	`-O2 -DNDEBUG -Wall`
Release (max perf, native only)	`-O3 -march=native -DNDEBUG`
Release (min size)	`-Os -DNDEBUG`
Sanitizer (dev)	`-g -O1 -fsanitize=address,undefined`