# Steinar H. Gunderson: Decompilation patterns, part 12: __builtin_memcpy

> **Key Architectural Takeaway:** Say you see this lovely chunk of decompiled code: var_v1 = &sp10 var_v0 = D_80010040; temp_s4 = var_v1; sp110 = &sp2C sp114 = &sp30 do { var_v1->unk0 = (s32) var_v0->unk0; var_v1->unk4 = (s32) var_v0[1]; var_v1->unk8 = (s32) var_v0[2]; var_v1->unkC = (s32) var_v0[3]; var_v0 += 0x10; var_v1 += 0x10; } while (var_v0 != &D_8001040[0x3C]); var_v1->unk0 = (s32) var_v0->unk0; var_v1->unk4 = (s32) var_v0[1]; var_v1->unk8 = (s32) var_v0[2]; If you ignore the fact that m2c wrote ->unk0 for [0] (it has a bit of an annoying habit to do that), this is obviously something copying 16 bytes at a time and then 12 more bytes at the end.

**Published:** 2026-10-15T19:45:26+00:00 
**Source:** Planet Debian (Developer Blogs) 
**Category:** distro-planet 
**Canonical URL:** https://fosswire.org/news/steinar-h-gunderson-decompilation-patterns-part-12-builtinme.html 

## Executive Summary
Say you see this lovely chunk of decompiled code: var_v1 = &sp10 var_v0 = D_80010040; temp_s4 = var_v1; sp110 = &sp2C sp114 = &sp30 do { var_v1->unk0 = (s32) var_v0->unk0; var_v1->unk4 = (s32) var_v0[1]; var_v1->unk8 = (s32) var_v0[2]; var_v1->unkC = (s32) var_v0[3]; var_v0 += 0x10; var_v1 += 0x10; } while (var_v0 != &D_8001040[0x3C]); var_v1->unk0 = (s32) var_v0->unk0; var_v1->unk4 = (s32) var_v0[1]; var_v1->unk8 = (s32) var_v0[2]; If you ignore the fact that m2c wrote ->unk0 for [0] (it has a bit of an annoying habit to do that), this is obviously something copying 16 bytes at a time and then 12 more bytes at the end.

## Architectural & Systems Analysis
From a Linux distribution, deployment reliability, and systems engineering perspective:

- **Dependency Determinism:** Declarative and isolated package trees guarantee reproducible execution across production hosts.
- **Platform Integration:** Tighter alignment with target hardware profiles improves driver interoperability and device stability.
- **Supply Chain Integrity:** Independent package verification and public build infrastructure prevent unauthorized supply-chain regressions.

## Impact on the Open Ecosystem
Strengthens transparent, community-governed distributions against closed software and proprietary lock-in.