Unreadable arguments and "debugging optimized function" warning

[antoineco]

Environment

dlv 1.1.0 (master @ 4e4ed02)
go 1.11.1
os darwin/amd64

What did you do?

With the following test code:

https://gist.github.com/antoineco/262c7dc7860ddd25ef5cd124d2a8ceb3

I ran:

$ dlv test ./
Type 'help' for list of commands.

(dlv) b k8s.io/client-go/testing.(*tracker).add
Breakpoint 1 set at 0x19ec06b for issue/vendor/k8s.io/client-go/testing.(*tracker).add() ./vendor/k8s.io/client-go/testing/fixture.go:309

(dlv) c
> issue/vendor/k8s.io/client-go/testing.(*tracker).add() ./vendor/k8s.io/client-go/testing/fixture.go:309 (PC: 0x19ec06b)
Warning: debugging optimized function
   304:                 }
   305:         }
   306:         return watches
   307: }
   308:
=> 309: func (t *tracker) add(gvr schema.GroupVersionResource, obj runtime.Object, ns string, replaceExisting bool) error {
   310:         t.lock.Lock()
   311:         defer t.lock.Unlock()
   312:
   313:         gr := gvr.GroupResource()
   314:

(dlv) args

What did you expect to see?

The args command prints the value of the function arguments.

What did you see instead?

Warning: debugging optimized function is printed and function arguments are unreadable.

(dlv) args
gvr = (unreadable empty OP stack)
ns = (unreadable could not find loclist entry at 0x4bed3 for address 0x1e3050b)
obj = (unreadable could not find loclist entry at 0x4bf0f for address 0x1e3050b)
replaceExisting = (unreadable could not find loclist entry at 0x4bf4a for address 0x1e3050b)
t = (unreadable could not find loclist entry at 0x4bf7f for address 0x1e3050b)
~r4 = (unreadable empty OP stack)

Important note

⚠️ Here comes the interesting part.

If one un-comments the commented out lines inside issue.go, the warning will not appear, and Delve will consistently print function arguments:

(dlv) args
gvr = issue/vendor/k8s.io/apimachinery/pkg/runtime/schema.GroupVersionResource {Group: "", Version: "v1", Resource: "events"}
ns = ""
obj = issue/vendor/k8s.io/apimachinery/pkg/runtime.Object(*issue/vendor/k8s.io/api/core/v1.Event) 0xc0000f8dd8
replaceExisting = false
t = (*issue/vendor/k8s.io/client-go/testing.tracker)(0xc0002c5400)
~r4 = (unreadable invalid interface type: could not find str field)

[aarzilli]

Duplicate of golang/go#27681

[barbu110]

it still happens to me after golang/go#27681 has been closed

[john8329]

Same, using the integrated debugger of Goland. The binary is built without optimization, and not all variables are readable.

Using the build flags (go 1.12):
go build -o=/... -gcflags="all=-N -l" ...

Error:
unreadable: could not find loclist entry at 0x... for address 0x...

[zhangguanzhang]

 -gcflags="all=-N -l" 

[asg0451]

 -gcflags="all=-N -l" 

this is amazing. it should be prominently displayed in the docs, as delve can be borderline unusable without it.

[KMankowski]

This still happens to me on macOS

macOS:reflection owner$ l
total 32
-rw-r--r--  1 owner  staff    52 Nov 10 00:40 go.mod
-rw-r--r--  1 owner  staff   569 Nov 13 14:14 walk.go
-rw-r--r--  1 owner  staff  1781 Nov 13 14:14 walk_test.go
-rw-r--r--  1 owner  staff   120 Nov 13 14:14 main.go
macOS:reflection owner$ go build -gcflags="all=-N -l"
macOS:reflection owner$ l
total 4384
-rw-r--r--  1 owner  staff       52 Nov 10 00:40 go.mod
-rw-r--r--  1 owner  staff      569 Nov 13 14:14 walk.go
-rw-r--r--  1 owner  staff     1781 Nov 13 14:14 walk_test.go
-rw-r--r--  1 owner  staff      120 Nov 13 14:14 main.go
-rwxr-xr-x  1 owner  staff  2227472 Nov 13 14:22 reflection
macOS:reflection owner$ dlv debug
Type 'help' for list of commands.
(dlv) break main.go:6
Breakpoint 1 set at 0x813114e,0x81314ce for (multiple functions)() ./main.go:6
(dlv) continue
> [Breakpoint 1] main.main() ./main.go:6 (hits goroutine(1):1 total:1) (PC: 0x813114e)
     1: package main
     2:
     3: import "fmt"
     4:
     5: func main() {
=>   6:         walk(struct{ Name string }{"Billy"}, func(s string) {
     7:                 fmt.Println(s)
     8:         })
     9: }
(dlv) args
(no args)
(dlv) s
> main.walk() ./walk.go:5 (PC: 0x81311d3)
     1: package main
     2:
     3: import "reflect"
     4:
=>   5: func walk(structToWalk interface{}, funcToCall func(string)) {
     6:         val := getVal(structToWalk)
     7:
     8:         switch val.Kind() {
     9:         case reflect.String:
    10:                 funcToCall(val.String())
(dlv) args
structToWalk = (unreadable error loading module data: read out of bounds)
funcToCall = (unreadable read out of bounds)
(dlv) exit
macOS:reflection owner$ go version
go version go1.23.3 darwin/amd64`