Delve getting stuck on intentional sigpanic trigger (via go-stack package)

[ThomasDotCodes]

I'm using the log15 package for logging, which uses the go-stack package for stack tracing.

There is a particular line/method within the go-stack package that intentionally triggers a sigpanic:

https://github.com/go-stack/stack/blob/master/stack.go#L228

Due to this line, the debugger just keeps breaking at this same place over and over, and never allows me to continue or step over it, constantly printing out "continuing" from this line:

https://github.com/derekparker/delve/blob/master/service/debugger/debugger.go#L393

Not sure where to start in troubleshooting this.

[aarzilli]

What operating system are you using? Can you give me some step to reproduce this problem?
I tried with this sample program:

package main

import (
    "fmt"

    "github.com/go-stack/stack"
)

func main() {
    s := stack.Trace().TrimRuntime()
    fmt.Printf("%v\n", s)
}

but I have no problem debugging it.

[LeeWong]

I am facing the same issue on windows 10 and here is the output of go env

set GOARCH=amd64
set GOBIN=
set GOEXE=.exe
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=windows
set GOPATH=...\go
set GORACE=
set GOROOT=C:\Go
set GOTOOLDIR=C:\Go\pkg\tool\windows_amd64
set CC=gcc
set GOGCCFLAGS=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=...\AppData\Local\Temp\go-build500025894=/tmp/go-build -gno-record-gcc-switches
set CXX=g++
set CGO_ENABLED=1

the file I try to debug is
https://github.com/go-kit/kit/blob/master/examples/stringsvc1/main.go

The delve debug output:
github.com/go-stack/stack.findSigpanic.func1() .../go/src/github.com/go-stack/stack/stack.go:228 (PC: 0x5faf0a)
223: }
224: }
225: }
226: }()
227: // intentional nil pointer dereference to trigger sigpanic

228: return *p
229: }()
230: return fn
231: }
232:
233: var sigpanic = findSigpanic()

[aarzilli]

I'm going to assume the original issue was about windows as well.

[BardoBravo]

Hi,
I also had the same issue when using go-lang debugger in Visual Code - Win10 by the way.
Hugs

[natdm]

I'm having the same issue.

go version: go1.8.1 darwin/amd64
OS: macOS
Text Editor: Atom
Delve Debugger Version: 0.12.2

Debug logs show:

Starting delve with config "Debug"
API server listening at: 127.0.0.1:2345
Started delve with config "Debug"
Adding breakpoint @ bindings/http_binding.go:57
Added breakpoint @ bindings/http_binding.go:57

Breakpoints show my breakpoint, but it doesn't get reached. It gets stuck at gopkg.in/stack.v1/stack.go#L228

// findSigpanic intentionally executes faulting code to generate a stack trace
// containing an entry for runtime.sigpanic.
func findSigpanic() *runtime.Func {
	var fn *runtime.Func
	var p *int
	func() int {
		defer func() {
			if p := recover(); p != nil {
				var pcs [512]uintptr
				n := runtime.Callers(2, pcs[:])
				for _, pc := range pcs[:n] {
					f := runtime.FuncForPC(pc)
					if f.Name() == "runtime.sigpanic" {
						fn = f
						break
					}
				}
			}
		}()
		// intentional nil pointer dereference to trigger sigpanic
		return *p // LINE 228
	}()
	return fn
}

Here is a repo I made to duplicate the issue. It uses glide package manager to ensure dependencies are the same.
https://github.com/natdm/findsigpanic_recreation

[aarzilli]

This can't be supported on the lldb backend, either switch to the native backend or do not use go-stack.

[dkushner]

I've opened this issue on go-stack to address this. Is there any way, in the mean time, to force delve to ignore either this specific exception or this file/package entirely to continue debugging? I'm guessing not, since the issue appears to be related to the fact that LLVM cannot intercept this signal at all, but worth a shot.

[aarzilli]

No, sorry.