What version of Go are you using (go version)?

Go tip (~1.9), gccgo gccgo (GCC) 8.0.0 20170725 (experimental)

What operating system and processor architecture are you using (go env)?

linux/amd64

What did you do?

package main

import (
        "fmt"
        "math"
)

var i int64 = 1<<32 + 1

func main() {
        fmt.Println(math.Ldexp(1.0, int(i)))
}

What did you expect to see?

With gc toolchain, the program above prints +Inf on linux/amd64. I believe this is the expected result.

What did you see instead?

With gccgo, the program above prints 2 on linux/amd64.

gccgo's math.Ldexp uses libc_ldexp, which is defined in C as double ldexp(double x, int exp). On linux/amd64, C's int is 32-bit whereas Go's int is 64-bit, causing this problem.

@ianlancetaylor