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expvar: panic: interface conversion: interface is nil, not expvar.Var #53422

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catenacyber opened this issue Jun 17, 2022 · 5 comments
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expvar: panic: interface conversion: interface is nil, not expvar.Var #53422

catenacyber opened this issue Jun 17, 2022 · 5 comments
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@catenacyber
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What version of Go are you using (go version)?

$ go version
go version go1.17.6 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/catena/Library/Caches/go-build"
GOENV="/Users/catena/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/catena/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/catena/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.17.6"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/catena/go/src/github.com/catenacyber/go/src/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/pp/dc1dtf9x2js3v0jx_m010nqr0000gn/T/go-build4237848497=/tmp/go-build -gno-record-gcc-switches -fno-common"
GOROOT/bin/go version: go version go1.17.6 darwin/amd64
GOROOT/bin/go tool compile -V: compile version go1.17.6
uname -v: Darwin Kernel Version 21.3.0: Wed Jan  5 21:37:58 PST 2022; root:xnu-8019.80.24~20/RELEASE_X86_64
ProductName:	macOS
ProductVersion:	12.2.1
BuildVersion:	21D62
lldb --version: lldb-1316.0.9.41
Apple Swift version 5.6 (swiftlang-5.6.0.323.62 clang-1316.0.20.8)
gdb --version: GNU gdb (GDB) 9.1

What did you do?

Run https://go.dev/play/p/L708GRIfgkv?v=gotip

What did you expect to see?

The program finishing and printing hello

What did you see instead?

panic: interface conversion: interface is nil, not expvar.Var

goroutine 1 [running]:
expvar.(*Map).Do(0xc000062240, 0xc000111ef8)
	/usr/local/go-faketime/src/expvar/expvar.go:227 +0x13c
expvar.(*Map).String(0xc000062240?)
	/usr/local/go-faketime/src/expvar/expvar.go:117 +0x9c
main.main()
	/tmp/sandbox2633615687/prog.go:14 +0x75

Program exited.

Found by https://github.com/catenacyber/ngolo-fuzzing on oss-fuzz
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=48049

Seems like fix for #52719 was not complete
@catenacyber
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Or maybe gotip on playground does not have latest patch...

@0xkaruru
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No,I see.

@seankhliao
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The playground has a slight lag for tip, you can get the version via fmt.Println(debug.ReadBuildInfo()), currently go devel go1.19-ecc268aa26 Thu Jun 16 01:03:59 2022 +0000, 5 commits behind the expvar fix.
Or go to https://gotipplay.golang.org/ which is the backend.

Doesn't repro locally on tip / go version devel go1.19-9068c6844d Thu Jun 16 21:58:40 2022 +0000 linux/amd64

@seankhliao
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Duplicate of #52719

@seankhliao seankhliao marked this as a duplicate of #52719 Jun 17, 2022
@seankhliao seankhliao closed this as not planned Won't fix, can't repro, duplicate, stale Jun 17, 2022
@catenacyber
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Thanks, I had wrongly read the fix was merged longer ago :-)

@golang golang locked and limited conversation to collaborators Jun 17, 2023
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@gopherbot @seankhliao @catenacyber @0xkaruru