Golang filepath.Walk panic error on large directory


func GetFiles() {
    err := filepath.Walk("C:\", walkpath)
    if err != nil {
        fmt.Printf(err.Error())
    }
}

Panic error:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x40 pc=0x46d0d6]

goroutine 1 [running]:
files.walkpath(0xc0820a8f80, 0xf, 0x0, 0x0, 0x664270, 0xc082408840, 0x0, 0x0)
        C:/project/src/files/files.go:11 +0x66
path/filepath.walk(0x529140, 0x3, 0x6641e8, 0xc082012240, 0x560d50, 0x0, 0x0)
        c:/go/src/path/filepath/path.go:370 +0x41c
path/filepath.Walk(0x529140, 0x3, 0x560d50, 0x0, 0x0)
        c:/go/src/path/filepath/path.go:396 +0xe8
files.GetFiles()
        C:/project/src/files/files.go:22 +0xc9
main.main()
        c:/project/src/main.go:12 +0x49
exit status 2

c:project>go build c:projectsrcmain.go

https://gobyexample.com/panic

How do you handle errors which occur during runtime?

Thanks!

asked Feb 18 '16 at 17:28

mbudge

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Check out this article; blog.golang.org/defer-panic-and-recover there's a common panic/recover pattern that gets used. Every error is different though. What does yours mean? If you're trying to say open a directory that doesn't exist or you don't have permissions to, recovering will just get control of execution back into your code, it's not gonna solve the problem of the directory being absent so you'll have to make some decisions about what should happen upon failure. – evanmcdonnal Feb 18 '16 at 17:37

Also, if you need to list very large directories, see stackoverflow.com/questions/34513460/… – JimB Feb 18 '16 at 17:53

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1 Answer

You're not checking the error, and trying to call a method on a nil os.FileInfo interface:

func walkpath(path string, f os.FileInfo, err error) error {
    if err != nil {
        fmt.Println(err)
    } else {    
        fmt.Printf("%s with %d bytes
", path,f.Size())
    }
    return nil
}

If you want to handle a panic at runtime, you can use recover. This should however be a last resort for unexpected panics. A panic is usually because of a programming error, and is intended to crash the program.

answered Feb 18 '16 at 17:47

JimB

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i encountered this. if err is not nil, then it is not safe to dereference f. invalid memory address or nil pointer dereference - usually means f would be nil. but in this case, it is because when err is not nil, f just happens to be garbage that you cannot dereference. ie: a pointer to something no longer valid, or a pointer with a strange value like "2" or "-5", etc. – Rob Dec 23 '16 at 2:36

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原文：https://stackoverflow.com/questions/35488397/golang-filepath-walk-panic-error-on-large-directory