英文:
how to debug revel build crash log?
问题
我想将我的应用程序投入生产，但在尝试执行revel build app时，我遇到了一个错误日志，我很难理解。
以下是日志的一部分：
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x20 pc=0x40c485]
goroutine 1 [running]:
main.func·002()
/home/johnny/data/go/src/github.com/revel/cmd/revel/rev.go:71 +0x7e
main.func·003(0xc208a4a400, 0x1001, 0x0, 0x0, 0x7ff4863a9238, 0xc2081ee420, 0x0, 0x0)
/home/johnny/data/go/src/github.com/revel/cmd/revel/util.go:96 +0x2b5
path/filepath.walk(0xc208617000, 0xff1, 0x7ff4863a9260, 0xc20883cff0, 0xc2085799c8, 0x0, 0x0)
/usr/lib/go/src/path/filepath/path.go:368 +0x430
日志中的其他行始终指向/usr/lib/go/src/path/filepath/path.go
日志的末尾是：
goroutine 5 [syscall]:
os/signal.loop()
/usr/lib/go/src/os/signal/signal_unix.go:21 +0x1f
created by os/signal.init·1
/usr/lib/go/src/os/signal/signal_unix.go:27 +0x35
这个日志让我想起了Objective-C，我知道调试它是多么困难。
也许我在路由中漏掉了一些东西？我在.gitignore中有一些文件（我不确定这是否与崩溃有关？）
英文:
I want to put my app in production but I am having trouble understanding this error log that I am getting while trying to do revel build app
This is part of log:
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x20 pc=0x40c485]
goroutine 1 [running]:
main.func·002()
/home/johnny/data/go/src/github.com/revel/cmd/revel/rev.go:71 +0x7e
main.func·003(0xc208a4a400, 0x1001, 0x0, 0x0, 0x7ff4863a9238, 0xc2081ee420, 0x0, 0x0)
/home/johnny/data/go/src/github.com/revel/cmd/revel/util.go:96 +0x2b5
path/filepath.walk(0xc208617000, 0xff1, 0x7ff4863a9260, 0xc20883cff0, 0xc2085799c8, 0x0, 0x0)
/usr/lib/go/src/path/filepath/path.go:368 +0x430
Other lines in log always reffer to this /usr/lib/go/src/path/filepath/path.go
and at the end of log is this:
goroutine 5 [syscall]:
os/signal.loop()
/usr/lib/go/src/os/signal/signal_unix.go:21 +0x1f
created by os/signal.init·1
/usr/lib/go/src/os/signal/signal_unix.go:27 +0x35
This log reminds me of objective C and I know how is hard to debug that.
Maybe I am missing something in routes somewhere? I have some files in .gitignore (i am not sure if that has to do something with a crash?)
答案1
得分: 1
你可能需要熟悉Go的堆栈跟踪。这里有一个不错的教程：http://www.goinggo.net/2015/01/stack-traces-in-go.html
基本上，你需要在堆栈跟踪中寻找处于"[running]"状态的goroutine（通常在堆栈跟踪的最顶部），并找出触发panic的那一行代码。
在这个例子中，github.com/revel/cmd/revel/util.go:96看起来是这样的：
if info.IsDir() {
err := os.MkdirAll(path.Join(destDir, relSrcPath), 0777)
if !os.IsExist(err) {
panicOnError(err, "Failed to create directory")
}
return nil
}
Panic报告的是panic: runtime error: invalid memory address or nil pointer dereference，所以很可能是info为nil（你也可以在调用path/filepath.Walk时看到它的值为0x0）。
看起来像是revel的一个bug，没有完整的代码和环境信息，无法确定。
英文:
You probably need to get familiar with Go stack traces. Here is nice tutorial: http://www.goinggo.net/2015/01/stack-traces-in-go.html
Basically, you have to look for the goroutine in the [running] state (it usually on the very top of the stack trace) and find out line, which triggered panic.
In this example, github.com/revel/cmd/revel/util.go:96 looks like this:
if info.IsDir() {
err := os.MkdirAll(path.Join(destDir, relSrcPath), 0777)
if !os.IsExist(err) {
panicOnError(err, "Failed to create directory")
}
return nil
}
Panic says panic: runtime error: invalid memory address or nil pointer dereference, so it must be info to be nil (you can see it also as 0x0 in the call to path/filepath.Walk.
Looks like revel bug, not sure without full code/env information.
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