| Issue |
163503
|
| Summary |
Supporting Windows SEH without the ORC runtime
|
| Labels |
orcjit
|
| Assignees |
|
| Reporter |
lhames
|
It'd be nice to get Windows SEH working without requiring the ORC runtime.
This would bring Windows into line with Darwin and Linux, both of which support exceptions in-process without the runtime.
`RtlAddFunctionTable` (https://learn.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-rtladdfunctiontable) and `RtlDeleteFunctionTable` seem to be the registration APIs.
`RtlAddFunctionTable` takes a base address and a pointer to a table where function addresses are expressed as 32-bit offsets from the base:
``
NTSYSAPI BOOLEAN RtlAddFunctionTable(
[in] PRUNTIME_FUNCTION FunctionTable,
[in] DWORD EntryCount,
[in] DWORD64 BaseAddress
);
```
I do not know whether the SEH runtime looks at any metadata at the base address, or whether it's used purely for address calculations, but I suspect the latter (or the various out-of-tree SEH experiments that people have gotten working would have blown up differently).
Assuming that `BaseAddress` is only used for address calculation then we can probably just find the lowest address in the graph and use that for each grab.
If `BaseAddress` needs to contain useful metadata (e.g. a COFF header) then we can do something similar to what we do for compact-unwind (see https://github.com/llvm/llvm-project/blob/d83fe1201e9d91da192d9292fea1a65579086e04/llvm/lib/ExecutionEngine/JITLink/CompactUnwindSupport.h#L634)
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