[GnoVM] - Cannot use pointer of an array as parameters of len & cap function

[MikaelVallenet]

Cannot use pointer of an array as parameters of len & cap function

Description

While I was working on implementing a value check for constants following this documentation, I realized that this code, which works in Go 1.17, doesn't work in Gno.

package main

func main() {
	exp := [...]string{"HELLO"}
	x := len(&exp)
	println(x)
}

Now, I don't know if this is intentional behavior, but if it is, I'd be delighted to have the justification and i will close the issue then. If not, it might be worth fixing to improve Go to Gno process.

Trace

panic running expression main(): unexpected type for len(): *[1]string
Machine State:Machine:
    CheckTypes: false
    Op: [OpHalt OpExec OpBody OpDefine OpReturn]
    Values: (len: 2)
          #1 (len func(x interface{})( int))
          #0 (main func()())
    Exprs:
    Stmts:
          #1 bodyStmt[0/0/2]=(const (println func(xs ...interface{})()))(x<VPBlock(1,1)>)*
          #0 return
    Blocks:
          @(107) Block(ID:0000000000000000000000000000000000000000:0,Addr:0xc00041e000,Source:func len(x interface {  })  int<...,Parent:0x0)
            x: (&(array[("HELLO" string)] [1]string) *[1]string)
            .res_0: (undefined)
 (s vals) @(107) Block(ID:0000000000000000000000000000000000000000:0,Addr:0xc0003bf030,Source:func len(x interface {  })  int<...,Parent:0xc0002fd530)
            x: (undefined)
            .res_0: (0 int)
 (s typs) @(107) [interface{} int]
    Blocks (other):
          #1 Block(ID:0000000000000000000000000000000000000000:0,Addr:0xc0002fbc20,Source:func main() { exp<VPBlock(1,0)> ...,Parent:0xc0002fb860)
            exp: (array[("HELLO" string)] [1]string)
            x: (undefined)
 (static) #1 Block(ID:0000000000000000000000000000000000000000:0,Addr:0xc0003f0c30,Source:func main() { exp<VPBlock(1,0)> ...,Parent:0xc0002fdb30)
            exp: (nil [1]string)
            x: (0 int)
    Frames:
          #1 [FRAME FUNC:len RECV:(undefined) (1 args) 4/1/0/2/2 LASTPKG:main LASTRLM:Realm(nil)]
          #0 [FRAME FUNC:main RECV:(undefined) (0 args) 1/0/0/0/1 LASTPKG:main LASTRLM:Realm(nil)]
    Exceptions:

Stacktrace: func(x interface{})( int)(&exp<VPBlock(1,0)>)
    .uverse/:5
main<VPBlock(1,0)>()
    main/const.gno:5

Your environment

• Go version (go1.17)

P.S: I also think it's a first good issue and i will see to fix it after i finish with const verification if no one fixed it before.

[leohhhn]

cc @deelawn @petar-dambovaliev

[notJoon]

Currently, the GetLength method does not handle the PointerValue type in TypedValue internally. It seemes the main cause of the problem.

https://github.com/gnolang/gno/blob/master/gnovm/pkg/gnolang/values.go#L2123-L2156

[thehowl]

Linear re-opened this, but it's incorrect.