[SR-5925] non-Darwin aarch64 fails to map va_list to CVaListPointer #48484
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I don't think that's sufficient. What we're really checking is that the CVaListPointer type defined in Swift is going to be layout-compatible with a va_list declared in C—not just as an argument, but also as, say, a member of a struct. Someone with actual AArch64 knowledge is going to have to look into this. |
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Comment by Paul Menage (JIRA) Ah, I'd not thought about the case of embedding it in a structure. Is it too late to rename CVaListPointer to just CVaList? Or is it better to put up with calling it CVaListPointer even though it's not a plain pointer on aarch64? |
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I don't think it's impossible to rename, although we might not be able to get rid of the old name. That would have to go through the Swift Evolution Process, though. cc @gparker42 |
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Additional Detail from JIRA
md5: 239df08cd73e174909d19b490bf6b43d
duplicates:
CVaListPointerdoes not gets converted tova_listonaarch64Issue Description:
When mapping C va_list-like types to CVaListPointer, ImportDecl.cpp checks
and ignores the mapping if the va_list type isn't the same size as a pointer. On non-Darwin aarch64, va_list is defined as a five-element structure rather than a pointer, so this check fails, and va_list C APIs don't get imported with Swift.CVaPointerList parameters.
However, since the aarch64 calling convention passes this struct by reference (as it's larger than two words) the ABI is basically the same - the value that gets passed as a va_list argument is a pointer-to-struct. So presumably this check should be relaxed on aarch64 at least.
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