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[Runtime] Properly handle unaligned reads in readTagBytes for layout … #66506

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Merged
merged 1 commit into from
Jun 10, 2023
Merged

[Runtime] Properly handle unaligned reads in readTagBytes for layout … #66506

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24 changes: 17 additions & 7 deletions stdlib/public/runtime/BytecodeLayouts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -182,12 +182,21 @@ static uint64_t readTagBytes(uint8_t *addr, uint8_t byteCount) {
switch (byteCount) {
case 1:
return addr[0];
case 2:
return ((uint16_t *)addr)[0];
case 4:
return ((uint32_t *)addr)[0];
case 8:
return ((uint64_t *)addr)[0];
case 2: {
uint16_t res = 0;
memcpy(&res, addr, sizeof(uint16_t));
return res;
}
case 4: {
uint32_t res = 0;
memcpy(&res, addr, sizeof(uint32_t));
return res;
}
case 8: {
uint64_t res = 0;
memcpy(&res, addr, sizeof(uint64_t));
return res;
}
default:
swift_unreachable("Unsupported tag byte length.");
}
Expand Down Expand Up @@ -608,7 +617,8 @@ void swift::swift_resolve_resilientAccessors(uint8_t *layoutStr,
writeBytes(layoutStr, writeOffset, getEnumTag);

size_t numCases = readBytes<size_t>(fieldLayoutStr, i);
size_t refCountBytes = readBytes<size_t>(fieldLayoutStr, i);
// skip ref count bytes
i += sizeof(size_t);

size_t casesBeginOffset =
layoutStrOffset + i + (numCases * sizeof(size_t));
Expand Down