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runtime: cgocallback signature mismatch #16326

josharian opened this issue Jul 11, 2016 · 3 comments


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commented Jul 11, 2016

While working on #11041, I encountered the following mismatch:


// cgocallback(void (*fn)(void*), void *frame, uintptr framesize, uintptr ctxt)
TEXT runtime·cgocallback(SB),NOSPLIT,$32-32


func cgocallback(fn, frame unsafe.Pointer, framesize uintptr)

The assembly implementation uses the ctxt parameter. However, there are other pure Go callers (in runtime/signal*.go) that call cgocallback directly, which means that there's junk in the ctxt parameter.

It appears that the right fix is to add ctxt to the prototype and add a ctxt parameter to the Go callers. Is this right? What value should ctxt have in those calls? Guidance appreciated.

cc @ianlancetaylor

@josharian josharian self-assigned this Jul 11, 2016

@ianlancetaylor ianlancetaylor added this to the Go1.7 milestone Jul 11, 2016


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commented Jul 11, 2016

@josharian I just saw that you self-assigned this; I already sent out a CL (


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commented Jul 11, 2016

I'm delighted for the help. :)


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commented Jul 12, 2016

CL mentions this issue.

@gopherbot gopherbot closed this in b30814b Jul 12, 2016

@golang golang locked and limited conversation to collaborators Jul 12, 2017

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