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.
-- Marcin
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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