x/tools/gopls/internal/analysis/modernize: slices.Delete modernizer is unsound (clears out s[len:cap]) #73686
Description
gopls version
The issue is for latest modernize
go env
See belowWhat did you do?
$ cat test.go
// You can edit this code!
// Click here and start typing.
package main
import (
"fmt"
)
func p(v int) *int {
return &v
}
func main() {
fmt.Println("Hello, 世界")
x := []*int{p(1), p(2), p(3), p(4)}
for i, member := range x {
println(i)
if *member == 2 {
x = append(x[:i], x[i+1:]...)
// Modernize will generate following code which will panic
// when last elemeny will be accessed
// x = slices.Delete(x, i, i+1)
}
}
fmt.Printf("%v\n", x)
}
$ go run test.go
Hello, 世界
0
1
2
3
[0xc0000120f0 0xc000012100 0xc000012108]
$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix test.go
$ cat test.go
// You can edit this code!
// Click here and start typing.
package main
import (
"fmt"
"slices"
)
func p(v int) *int {
return &v
}
func main() {
fmt.Println("Hello, 世界")
x := []*int{p(1), p(2), p(3), p(4)}
for i, member := range x {
println(i)
if *member == 2 {
x = slices.Delete(x, i, i+1)
// Modernize will generate following code which will panic
// when last elemeny will be accessed
// x = slices.Delete(x, i, i+1)
}
}
fmt.Printf("%v\n", x)
}
$ go run test.go
Hello, 世界
0
1
2
3
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4912d7]
goroutine 1 [running]:
main.main()
test.go:20 +0x1d7
exit status 2What did you see happen?
Hello, 世界
0
1
2
3
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4930b7]
goroutine 1 [running]:
main.main()
/tmp/sandbox3797330105/prog.go:20 +0x1d7
What did you expect to see?
Hello, 世界
0
1
2
3
[0xc000010080 0xc000010090 0xc000010098]
Program exited.
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