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Support unaligned C13 debug subsection lengths - #170
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The length does not include the padding that follows it up to the next multiple of four bytes. PDBs from link.exe never hit this because their subsection lengths already are multiples of four. But the .NET Native toolchain (ILC) writes unpadded lengths for its FuncMDTokenMap and TypeMDTokenMap subsections. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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The length does not include the padding that follows it up to the next multiple of four bytes.
PDBs from link.exe never hit this because their subsection lengths already are multiples of four. But the .NET Native toolchain (ILC) writes unpadded lengths for its FuncMDTokenMap and TypeMDTokenMap subsections and, unlike .NET NativeAOT, doesn't go through link.exe.
Looking at the reference implementation, it does treat padding as separate from the length:
cvdump: its.debug$Swalker aligns its offset to 4 before each subsection header, then advances by the rawcb(cvdump.cpp#L1683-L1719, #L1893-L1900).dumpsym7.cpp: it does the same for a PDB module's C13 buffer (#L6240-L6299).AppendSubSectionToBufferappends the raw subsection bytes, then pads the buffer to a multiple of 4 (mod.cpp#L469-L484).