On Thu, May 2, 2019 at 11:18 AM Marcin Romaszewicz <marc...@gmail.com> wrote:
>
> If that's the actual problem, you'd just be masking it, and producing an
> invalid "x". Look here:
>
> func (r *Subid_info) Prepare_subid_logic(){
> r.Second_subid_8=fmt.Sprintf("1%07v", r.Second_subid) ----> panic happens
> here.
> }
>
> r.Second_subid is in an invalid state which normal Go code could not create.
> This means that some other goroutine might be in the middle of changing its
> value at the same time, and you have a race condition, so Ian Lance Taylor's
> suggestion to run using the race detector is probably the best bet.
I agree. Look very closely at how r.Second_subid is set. The
backtrace shows that it is a value of type string that is invalid.
Ian
> On Thu, May 2, 2019 at 11:13 AM Burak Serdar <bser...@ieee.org> wrote:
>>
>> On Thu, May 2, 2019 at 11:31 AM XXX ZZZ <emartinez1...@gmail.com> wrote:
>> >
>> > Hello,
>> >
>> > We are having a random panic on our go application that is happening once
>> > every million requests or so, and so far we haven't been able to reproduce
>> > it nor to even grasp what's going on.
>> >
>> > Basically our code goes like:
>> >
>> > type Subid_info struct{
>> > Affiliate_subid string
>> > Second_subid string
>> > Second_subid_8 string
>> > S2 string
>> > Internal_subid string
>> > Internal_subid_9 string
>> > Internal_subid_12 string
>> > Result string
>> > }
>> >
>> > func (r *Subid_info) Prepare_subid_logic(){
>> > r.Second_subid_8=fmt.Sprintf("1%07v", r.Second_subid) ----> panic
>> > happens here.
>> > }
>> >
>> > And the trace we get is:
>> >
>> > panic: runtime error: invalid memory address or nil pointer dereference
>> > [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x466b6e]
>> >
>> > goroutine 17091 [running]:
>> > unicode/utf8.RuneCountInString(0x0, 0x5, 0xc048c275a8)
>> > /usr/local/go/src/unicode/utf8/utf8.go:411 +0x2e
>> > fmt.(*fmt).padString(0xc023c17780, 0x0, 0x5)
>> > /usr/local/go/src/fmt/format.go:113 +0x134
>> > fmt.(*fmt).fmtS(0xc023c17780, 0x0, 0x5)
>> > /usr/local/go/src/fmt/format.go:347 +0x61
>> > fmt.(*pp).fmtString(0xc023c17740, 0x0, 0x5, 0xc000000076)
>>
>> Right here in fmtString, the function gets a 0x0, 0x5 arg, which is I
>> believe a string of length 5 with a nil slice. So it looks like
>> somehow r.Second_subid has nil buffer here. When a string is used as
>> an interface{}, afaik, the interface keeps the value, not the pointer
>> to the string. So I can't see how this is possible. But I wonder if
>> copying the value before sprintf could fix it:
>>
>> x:=r.Second_subid
>> r.Second_subid_8=fmt.Sprintf("1%07v", x)
>>
>>
>>
>>
>> > /usr/local/go/src/fmt/print.go:448 +0x132
>> > fmt.(*pp).printArg(0xc023c17740, 0x9978e0, 0xc016a68a30, 0x76)
>> > /usr/local/go/src/fmt/print.go:684 +0x880
>> > fmt.(*pp).doPrintf(0xc023c17740, 0xa6e22f, 0x5, 0xc048c27818, 0x1, 0x1)
>> > /usr/local/go/src/fmt/print.go:1112 +0x3ff
>> > fmt.Sprintf(0xa6e22f, 0x5, 0xc048c27818, 0x1, 0x1, 0x80, 0xa36200)
>> > /usr/local/go/src/fmt/print.go:214 +0x66
>> > code/sharedobjects/sources.(*Subid_info).Prepare_subid_logic(0xc019292f80,
>> > 0x2)
>> >
>> > Given that we can't reproduce it, what's the logical way to debug this and
>> > find out what's happening?
>> >
>> > Thanks!
>> >
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