pe: skip raw writes for virtual-only sections#541
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PE sections such as .bss can reserve virtual memory without carrying raw on-disk data. The writer previously expanded those virtual bytes and could write zeroes at file offset 0, corrupting the DOS/PE headers during rewrite. Treat zero-raw-size sections as virtual-only, preserve their section table entries, and skip writing nonexistent section bytes. The regression coverage uses synthetic section data so the test does not require a bundled executable fixture. Constraint: Virtual-only PE sections may legally have SizeOfRawData == 0 and PointerToRawData == 0
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Summary
SizeOfRawData == 0as virtual-only on diskRoot cause
Some PE files, including the local Free Pascal sample used to reproduce this, contain a
.bsssection with a nonzero virtual size but no raw on-disk data. The writer previously expanded that virtual-only section into zero bytes and wrote them atPointerToRawData == 0, which could corrupt the DOS/PE headers.Validation
cargo fmt --checkcargo testfreepascal_cli.exerewrite remained byte-identical by SHA256Notes
This is a narrow PE writer fix and does not special-case Free Pascal binaries. The regression test uses synthetic section data instead of adding a binary executable fixture.