尝试异常替代方案以保护应用程序不崩溃

Question

I have a Go application for scrape URLs. The problem is it sometimes crashes and returns this error:

panic: runtime error: slice bounds out of range
goroutine 1 [running]:
main.dom6(0x187d4140, 0x8, 0x187d4179, 0x5, 0x187c0800, 0x6, 0x13, 0x83007cb)
        /root/sswork.go:326 +0x6b
main.sub(0x187d4140, 0x8, 0x84464e0, 0x6, 0x6, 0x187d4140, 0x8, 0x187d4179, 0x5, 0x187c0800, ...)
        /root/sswork.go:298 +0xb3
main.main()
        /root/sswork.go:615 +0xccb

on line 298 is this function :

294: // try our list of substitutions, if one works return it
295: func sub(str string, xs []subs, u string, p string, h string) string {
296:    for _, x := range xs {
297:        if strings.Contains(str, x.pattern) {
298:            return strings.Replace(str, x.pattern, x.fn(u, p, h), 1)
299:        }
300:    }
301:    return str
302:}

How can I solve my problem so it doesn't crash the application any more?

324: // the first 6 characters of the above
325: func dom6(u string, p string, d string) string {
326:    return domfull(u, p, d)[0:6]
327: }

Answer 1

The error is at line 326, not 298. And to avoid such panics, perform manual index check before attempting to index or slice a slice, array or string.

You indicated that the code at line 298 is:

// the first 6 characters of the above
func dom6(u string, p string, d string) string {
    return domfull(u, p, d)[0:6]
}

Check the length of the string returned by domfull() before attempting to slice it, e.g.:

func dom6(u string, p string, d string) string {
    df := domfull(u, p, d)
    if len(df) < 6 {
        return df
    }
    return df[:6]
}