Fix selector forwarding on x64 Windows #313
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@davidchisnall This is the simplest repro I could create so far. Looks like this issue happens on 64-bit Windows only; 32-bit Windows appears to be fine. |
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- %r9 for Windows - %rcx for Unix
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davidchisnall
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This was referenced Nov 18, 2024
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As described in #312, selector forwarding does not appear to be working correctly on Windows. This becomes apparent when accessing
[self]. This PR updates the Forward test to access an instance variable, exposing the issue, and proposes a fix.The root cause appears to be that the
rcxregister is being overwritten afterslowMsgLookupreturns. On Unix,rcxis the fourth argument; on Windows, it is the first argument. Introduce aFOURTH_ARGUMENTvariable to ensure we usercxon Unix andr9on Windows to refer to the fourth argument.Closes #312