cmd/link: impossible r.Sym.Cfunc == 1 condition in internal/ld/lib.go #13257
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I think this is some of the code I was talking about here: https://groups.google.com/d/msg/golang-dev/KK5olmcQ6U4/RdnUHhkVeA8J |
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@mwhudson Yep, though whereas you were pointing out the code was unneeded after the c2go conversion (until rsc later repurposed it for go:systemstack), I'm pointing out that "cfunc == 1" is (and has always been) impossible within the linker. Because of an asymmetry between the code responsible for writing cfunc into a Go object file and reading it back in, setting cfunc==1 in the compiler results in setting cfunc==2 in the linker, and there's no other assignments of cfunc=1 within the linker. |
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Ah OK :-) |
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Yes, func checkgo can be deleted. |
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Fixed by 1012892. |
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cmd/link has this test in a block of code labeled "Mark every Go-called C function with cfunc=2, recursively.":
As far as I can tell, the only assignments to cmd/link/internal/ld.LSym's Cfunc field are:
neither of which can set it to 1.
(There's a "ptxt.From.Sym.Cfunc = 1" assignment in compile/internal/gc/pgen.go, but that's referring to the Cfunc field of an cmd/internal/obj.LSym.)
FWIW, I tracked this check back to https://golang.org/cl/135170044 (0bb14d7), and it appears to have been impossible even then (though less obvious since cmd/cc and cmd/ld used the same LSym type).
CC @rsc @randall77
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