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gx: don't underflow the index reservation for fans/strips with fewer than 3 vertices - #301
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…than 3 vertices (u32(vtxCount) - 3) wraps around for 0-2 vertices, so reserve_extra asks for about 8 GiB. Degenerate primitives like these are legal GX and some games emit them.
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prepare_idx_bufferreserves((u32(vtxCount) - 3) * 3 + 3) * sizeof(u16)bytes for triangle fans and strips. With 0-2 vertices the subtraction wraps around, soreserve_extraasks for about 8 GiB. Degenerate primitives like that are valid GX. Super Mario Galaxy emits them, and we hit this while porting it to PC.The fix reserves
vtxCountindices when there are fewer than 3 vertices, and computes insize_totherwise. The loops that follow are unchanged; they emit no triangle for such primitives.We've carried this patch in a Super Mario Galaxy PC port (https://github.com/yacineolivier-maker/petari-pc) for several weeks. That port, this patch and this description were written with AI assistance (Claude).