Open
Description
package main
import (
"fmt"
"math/big"
)
type BigInt big.Int
func main() {
_2 := big.NewInt(2)
_100 := big.NewInt(100)
z := new(big.Int)
z.Exp(_2, _100, nil)
// Exp works with a nil modulus
fmt.Printf("z = %d\n", z)
// Now make a nil type alias
var y *BigInt = nil
// Should now be a nil *big.Int
// This line doesn't error, but x causes a nil pointer exception wherever it is used
x := (*big.Int)(y)
// Note the supressed nil pointer exception
fmt.Printf("x = %d\n", x)
// This causes a nil pointer exception
z.Exp(_2, _100, x)
fmt.Printf("z = %d\n", z)
}Works fine under go producing this output
z = 1267650600228229401496703205376
x = <nil>
z = 1267650600228229401496703205376
However it produces this output under gopherjs
z = 1267650600228229401496703205376
x = %!d(PANIC=runtime error: invalid memory address or nil pointer dereference)
Uncaught Error: runtime error: invalid memory address or nil pointer dereference
at $callDeferred (gopherjs_exp_bug.js:1419)
at $panic (gopherjs_exp_bug.js:1458)
at throw$1 (runtime.go:225)
at Object.$throwNilPointerError (gopherjs_exp_bug.js:29)
at Object.get (gopherjs_exp_bug.js:309)
at Object.$packages.math/big.Int.ptr.Exp (int.go:463)
at main (gopherjs_exp_bug.go:33)
at $init (gopherjs_exp_bug.js:28464)
at $goroutine (gopherjs_exp_bug.js:1478)
at $runScheduled (gopherjs_exp_bug.js:1518)
at $schedule (gopherjs_exp_bug.js:1534)
at $go (gopherjs_exp_bug.js:1510)
at gopherjs_exp_bug.js:28475
at gopherjs_exp_bug.js:28478
The problem is something to do with the nil type alias for big.Int - it produces a nil pointer exception when used. I'm not sure whether this is specific to big.Int or not though.
Tested with the latest gopherjs (1babbf9) using gopherjs serve and Chrome 69.0.3497.100