Walk an array of struct values at the struct's own stride - #13
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estebanzimanyi merged 2 commits intoSep 2, 2026
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A C type the mapping table does not name falls through to IntPtr, the pointer-width opaque handle. The `_t` spellings libclang leaves unreduced — int8_t through uint64_t — and `unsigned char` are absent from that table, so 530 of the 4825 bound functions declared a scalar at pointer width: 246 int64_t, 140 uint64_t, 38 uint32_t and 24 unsigned char arguments, and 72 int64_t, 58 uint64_t, 56 uint32_t and one unsigned char returns. A uint32_t returned as IntPtr reads eight bytes of a register the ABI defines four of, so the value carries whatever the upper half held. The enum types come from the catalog's own `enums` rather than from names listed one at a time. The five listed names covered MeosType, interpType and tempSubtype, missed IndexSearchOp, SPTreeKind, MeosPixType, MeosOper, SkipListType and nullHandleType across 43 further parameters and returns, and one of them — spanType — names no catalog enum at all. Reading the set from the catalog is what keeps the next enum from arriving as a pointer.
An array return whose element is a catalog struct — Span, TBox, STBox,
Match, GeoPoseFrame — is unpacked as an array of pointers: element i is
read as the eight bytes at i * IntPtr.Size and used as an address, which
for a 24-byte Span is that Span's own spantype, basetype and bound flags.
68 wrappers return such an array, `spanset_spans`, `set_spans`,
`geo_stboxes` and `tnumber_tboxes` among them.
The stride is the struct's size, taken from the field layout the catalog
records: every field at the offset the catalog gives it, the whole padded
to a multiple of its widest field — Span 24, TBox 56, STBox 80, Match 8.
Element i is the address i strides into the block, so `spanset_spans` over
`{[8, 10], [11, 12]}` answers those two spans instead of two addresses
that happened never to be dereferenced.
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An array return whose element is a catalog struct — Span, TBox, STBox,
Match, GeoPoseFrame — is unpacked as an array of pointers: element i is
read as the eight bytes at i * IntPtr.Size and used as an address, which
for a 24-byte Span is that Span's own spantype, basetype and bound flags.
68 wrappers return such an array,
spanset_spans,set_spans,geo_stboxesandtnumber_tboxesamong them.The stride is the struct's size, taken from the field layout the catalog
records: every field at the offset the catalog gives it, the whole padded
to a multiple of its widest field — Span 24, TBox 56, STBox 80, Match 8.
Element i is the address i strides into the block, so
spanset_spansover{[8, 10], [11, 12]}answers those two spans instead of two addressesthat happened never to be dereferenced.