Thanks for commenting, a few supplements.
*# 1. Version of Go?*
We observed the issue with both go1.20.5 and go1.18.10 on linux/amd64
(centos)
*# 2. Context?*
All panics we observed so far are from either
*strconv.FormatInt -> strconv.formatBits* chain, or
*strconv.FormatUint -> strconv.formatBits* chain
where the base is always 10.
// typical call site, toId is an "*int64".
if com_count > 1 {
com_string = anchor + "," + strconv.FormatInt(*toId, 10)
}
*# 3. If your program using pure Go (statically linked) or Cgo?*
Binary was built with CGO_ENABLED=1 and -buildmode=exe.
All panic call sites we observed so far are "pure go", that is, no C
calling go path.
*# 4. panic stack trace*
panic: runtime error: index out of range [18446744073708732603] with length
200
goroutine 1 [running]:
strconv.formatBits({0x0?, 0x0?, 0x0?}, 0xc09e00b750?, 0x1?, 0x1?, 0x0?)
/usr/lib/go-1.20/src/strconv/itoa.go:140 +0x4b9
strconv.FormatInt(0x0?, 0xc07393df80?)
/usr/lib/go-1.20/src/strconv/itoa.go:29 +0xa5
...
On Thursday, August 17, 2023 at 12:56:17 PM UTC+8 Kurtis Rader wrote:
> Insufficient information. Version of Go? Since formatBits is private we
> need to see the actual code of a call to a public API that resulted in the
> call to formatBits that failed. Also, show us the literal panic stack.
> Showing us the assembly code with no context is not useful. If your program
> using pure Go (statically linked) or Cgo? Wild guesses, what I used to call
> SWAGS (silly wild ass guesses) as a Unix support engineer, are seldom
> useful. If your guess is scientifically informed that is a different matter
> but you should be able to articulate why you think your guess is more
> likely to be true than a random coin flip.
>
> On Wed, Aug 16, 2023 at 8:31 PM metronome <[email protected]> wrote:
>
>> Hi,
>>
>> We ran into a weird *out of range* issue of *strconv.formatBits*, hope
>> someone can shed a light on what could be the root cause, any comment is
>> highly appreciated.
>>
>> problem description:
>> * random out of range at code
>> <https://github.com/golang/go/blob/release-branch.go1.20/src/strconv/itoa.go#L140>,
>>
>> most of the time the indexing is a huge int but we observed at least one
>> exception (#2).*
>>
>> * #1: runtime error: index out of range [18446744073709449339] with
>> length 200*
>> * #2: runtime error: index out of range [102511] with length 200*
>>
>> Wild guesses:
>> 1. The machine code seems to suggest it's unlikely a data race or memory
>> corruption? But perhaps
>> relevant registers, like R10, had been saved and restored, then it might
>> be due to stack corruption?
>> Given that R12 is scratch reg, is it possible that R12 is clobbered
>> somehow, say, by signal handling?
>>
>> ===================================================================
>> 0x0000000000495b0a<+810>: mov %rdi,%r10
>>
>> 0x0000000000495b0d<+813>: shr %rdi
>>
>> 0x0000000000495b10<+816>: mov %rax,%rsi
>>
>> 0x0000000000495b13<+819>: movabs $0xa3d70a3d70a3d70b,%rax
>>
>> 0x0000000000495b1d<+829>: mov %rdx,%r11
>>
>> 0x0000000000495b20<+832>: mul %rdi
>>
>> 0x0000000000495b23<+835>: shr $0x5,%rdx
>>
>> * 0x0000000000495b27<+839>: imul $0x64,%rdx,%r12*
>>
>> * 0x0000000000495b2b<+843>: sub %r12,%r10*
>>
>> * 0x0000000000495b2e<+846>: lea (%r10,%r10,1),%rax*
>>
>> 0x0000000000495b32<+850>: lea 0x1(%rax),%rax
>>
>> 0x0000000000495b36<+854>: nopw 0x0(%rax,%rax,1)
>>
>> 0x0000000000495b3f<+863>: nop
>>
>> 0x0000000000495b40<+864>: cmp $0xc8,%rax
>>
>> 0x0000000000495b46<+870>: jae 0x495c8f
>> <strconv.formatBits+1199>
>>
>> --
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>>
>> <https://groups.google.com/d/msgid/golang-nuts/ff804d4c-24ee-480d-8ed1-219f9b8d7cbcn%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
>
> --
> Kurtis Rader
> Caretaker of the exceptional canines Junior and Hank
>
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