strange stack trace when panic

[winlin]

Hi, I'm confused by the stack trace when panic, and I have searched both in history topics and google.

If I use panic, the stack is fine, code is https://play.golang.org/p/Yb7fYW9ro3 , output is:

panic: Panic from user

goroutine 1 [running]:

main.causedPanic()

	/tmp/sandbox078566511/main.go:11 +0x60

main.run()

	/tmp/sandbox078566511/main.go:7 +0x20

main.main()

	/tmp/sandbox078566511/main.go:4 +0x20

But if there is a runtime panic, the stack is completely unreadable, code is https://play.golang.org/p/MHKPG5uFFn , output is:

panic: runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:

main.main()

	/tmp/sandbox277759147/main.go:4 +0x4

If I add a defer to the last function, the stack comes back, code is https://play.golang.org/p/V7qDdyt_4Z , output is:

panic: runtime error: invalid memory address or nil pointer dereference

goroutine 1 [running]:

main.causedPanic()

	/tmp/sandbox416089181/main.go:13 +0x48

main.run()

	/tmp/sandbox416089181/main.go:7 +0x20

main.main()

	/tmp/sandbox416089181/main.go:4 +0x20

Why it's diferent when there is a empty defer? It confused me.

[Dave Cheney]

Try building your program with -gcflags="-l" to disable inlining. If that restores the stacktrace, then it's inlining. The good news is this should be fixed with Go 1.9

[winlin]

When I run with -gcflags="-l", it works~

winlin$ go run -gcflags="-l" t.go 

panic: runtime error: invalid memory address or nil pointer dereference

[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x104bf82]

goroutine 1 [running]:

main.causedPanic()

/Users/winlin/git/t.go:13 +0x2

main.run()

/Users/winlin/git/t.go:7 +0x20

main.main()

/Users/winlin/git/t.go:4 +0x20

exit status 2 

The code is here: https://play.golang.org/p/MHKPG5uFFn 

It seems it's caused by inling.

Thanks a lot!

[binl...@gmail.com]

awsome

在 2017年6月7日星期三 UTC+8下午4:25:35，Dave Cheney写道：