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

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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.

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.

Distribution Engineering & Packaging Ecosystem Audit

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.