runtime: crash when ending checkmarks

[MikeMitchellWebDev]

What version of Go are you using (go version)?

$ go version
go version devel go1.24-f3b0219 Tue Aug 27 21:02:02 2024 +0000 darwin/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/Users/mm/Library/Caches/go-build'
GOENV='/Users/mm/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/mm/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/mm/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/mm/go/src/github.com/MikeMitchellWebDev/go_checkmark'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/mm/go/src/github.com/MikeMitchellWebDev/go_checkmark/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='devel go1.24-f3b0219 Tue Aug 27 21:02:02 2024 +0000'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/mm/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='/usr/bin/clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/mm/go/src/github.com/MikeMitchellWebDev/go_checkmark/src/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/5y/wtzzmjlj5v52pg7wr8ptbg_m0000gp/T/go-build641299882=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOROOT/bin/go version: go version devel go1.24-f3b0219 Tue Aug 27 21:02:02 2024 +0000 darwin/amd64
GOROOT/bin/go tool compile -V: compile version devel go1.24-f3b0219 Tue Aug 27 21:02:02 2024 +0000
uname -v: Darwin Kernel Version 20.6.0: Thu Jul  6 22:12:47 PDT 2023; root:xnu-7195.141.49.702.12~1/RELEASE_X86_64
ProductName:	macOS
ProductVersion:	11.7.10
BuildVersion:	20G1427
lldb --version: lldb-1300.0.42.3
Swift version 5.5.2-dev

What did you do?

./GODEBUG=gccheckmark=1 ./gc_knobs
./gc_knobs_client -g 200 -s 1 -r 10 -p "/Users/mm/backbone"

(both gc_knobs_client and gc_knobs are available on my github https://github.com/MikeMitchellWebDev/gc_knobs and https://github.com/MikeMitchellWebDev/gc_knobs_client)

What did you expect to see?

What did you see instead?

see attached file workbufs.txt

[gabyhelp]

Related Issues and Documentation

• runtime: gccheckmark does nothing? #69074
• Test #67906 (closed)
• go clean #36248 (closed)
• s #52224 (closed)
• go #64466 (closed)
• clear #57553 (closed)
•  #52089 (closed)
• c #35257 (closed)
• sb #53220 (closed)
• test #43061 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[timothy-king]

Error message is:

GC work not flushed fatal error : cannot free workbufs when work.free != 0

Likely start is endCheckmarks() in src/runtime/mcheckmark.go.

CC @golang/runtime

[gopherbot]

Change https://go.dev/cl/608915 mentions this issue: runtime: fix GODEBUG=gccheckmark=1 and add smoke test