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runtime/cgo: pthread attribute object leaked on every new thread on BSD, illumos and AIX #82242
Description
Go version
go version go1.27.2 openbsd/arm64
Output of go env in your module/workspace:
AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN='/root/go/bin'
GOCACHE='/root/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1885286381=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='arm64'
GOHOSTOS='openbsd'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/root/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='openbsd'
GOPACKAGESDRIVER=''
GOPATH='/root/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/root/go1.27.2'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/root/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/root/go1.27.2/pkg/tool/openbsd_arm64'
GOVCS=''
GOVERSION='go1.27.2'
GOWORK=''
PKG_CONFIG='pkg-config'What did you do?
Audited runtime/cgo on OpenBSD/arm64.
runtime/cgo/pthread_unix.c calls pthread_attr_init but never calls pthread_attr_destroy. Several libcs allocate in pthread_attr_init, so every cgo-created thread leaks one heap object.
The non-cgo OpenBSD path in runtime/os_openbsd.go already destroys its attribute object.
Example:
package main
/* static void noop(void) {} */
import "C"
import "runtime"
func main() {
for range 300_000 {
done := make(chan struct{})
go func() {
runtime.LockOSThread()
C.noop()
close(done)
}()
<-done
}
}Run it:
go build -o leak leak.go
(ulimit -c 0; ulimit -d 65536; ./leak)What did you see happen?
The native heap grows by about 50 bytes per retired thread. With the ulimit the process aborts with:
runtime: remapping stack memory 0x454428000 32768 a=0x0 err=12
fatal error: remapping stack memory failed
runtime: remapping stack memory 0x454480000 32768 a=0x0 err=12
fatal error: runtime: remapping stack memory 0x45440a000 32768 a=0x0 err=12
fatal error: remapping stack memory failed
remapping stack memory failed
What did you expect to see?
Each successfully init'd attribute should be destroyed after pthread_create. In the example code, the memory usage should plateau and exit without a fault.
I can send a CL.
Activity
gopherbot commentedon Oct 15, 2026
Change https://go.dev/cl/849468 mentions this issue:
runtime/cgo: destroy pthread attributes after use