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cmd/compile: suspicious symbol generation for args_stackmap #31615

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mdempsky opened this issue Apr 22, 2019 · 3 comments
Closed

cmd/compile: suspicious symbol generation for args_stackmap #31615

mdempsky opened this issue Apr 22, 2019 · 3 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@mdempsky
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In CL 171464, @randall77 fixed a lookup(fmt.Sprintf(...)) call in pgen.go, but we noticed another similarly suspicious line of code for generating args_stackmap symbols. However, Keith reports that applying the same fix didn't work: https://go-review.googlesource.com/c/go/+/171464/1/src/cmd/compile/internal/gc/pgen.go#39

Seems worth looking into and understanding whether the existing code is safe.
@mdempsky mdempsky added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Apr 22, 2019
@mdempsky mdempsky added this to the Unplanned milestone Apr 22, 2019
@cuonglm
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cuonglm commented Feb 7, 2020

@randall77 Can you elaborate what is exactly the same fix?

Does it mean:

lsym := Ctxt.Lookup(fn.Func.lsym.Name + ".args_stackmap")

or:

lsym := Ctxt.Lookup(fn.funcname()+ ".args_stackmap")

@cuonglm
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cuonglm commented Mar 12, 2020

Seems worth looking into and understanding whether the existing code is safe.

@mdempsky it seems to be safe.

Method without body can only occur via //go:linkname (method via assembly won't happen in Go 1 #4978) and //go:linkname already has full path. So something like this:

package d

import _ "unsafe"

//go:linkname a a.IndexController.M
func a() {}

//go:linkname b b.IndexController.M
func b() {}

will work.

@gopherbot
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Change https://golang.org/cl/223238 mentions this issue: cmd/compile: skip generating args_stackmap for "pulled" funcs

@golang golang locked and limited conversation to collaborators Mar 23, 2021
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