by foru607:

fmt package BUG:
------------------------------
package main

import (
    "fmt"
)

func main() {
    fmt.Printf("%#064x\n", 1) // fail, panic
    fmt.Printf("%#064b\n", 1) // ok
    fmt.Printf("%#064o\n", 1) // ok
    fmt.Printf("%#064d\n", 1) // ok

    fmt.Printf("%#070x\n", -1) // fail, panic
    fmt.Printf("%#070b\n", -1) // fail, panic
    fmt.Printf("%#070o\n", -1) // fail, panic
    fmt.Printf("%#070d\n", -1) // fail, panic
}
------------------------------



My environment:
------------------------------
Ubuntu 12.04
go1.2rc4.linux-386.tar.gz
------------------------------



Bug fix approach:
------------------------------
file: go/src/pkg/fmt/format.go
line: 13
change to: nByte = 67

file: go/src/pkg/fmt/format.go
line: 185
add:
if prec > nByte-3 {
    prec = nByte - 3
    f.zero = false
}
------------------------------



Correct results:
------------------------------
0x0000000000000000000000000000000000000000000000000000000000000001
0000000000000000000000000000000000000000000000000000000000000001
0000000000000000000000000000000000000000000000000000000000000001
0000000000000000000000000000000000000000000000000000000000000001
   -0x0000000000000000000000000000000000000000000000000000000000000001
     -0000000000000000000000000000000000000000000000000000000000000001
     -0000000000000000000000000000000000000000000000000000000000000001
     -0000000000000000000000000000000000000000000000000000000000000001
------------------------------