runtime: recover added in range-over-func loop body doesn't stop panic propagation / segfaults printing error #71675
Description
Go version
go version go1.23.2 darwin/amd64
Output of go env in your module/workspace:
GO111MODULE='on'
GOARCH='amd64'
GOBIN=''
GOCACHE='/Users/acorn/Library/Caches/go-build'
GOENV='/Users/acorn/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/acorn/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/acorn/go'
GOPRIVATE=''
GOPROXY='direct'
GOROOT='/Users/acorn/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.2.darwin-amd64'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/acorn/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.2.darwin-amd64/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.23.2'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/acorn/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/acorn/go-demo/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/6c/6skkl1zn2p9fcx2r70v0kyc00000gn/T/go-build362480746=/tmp/go-build -gno-record-gcc-switches -fno-common'What did you do?
When traversing an iterative function, there are some peculiar behaviors that arise concerning the defer within the loop, the panic in the outer function surrounding the loop, and the panic within the iterative function itself.
Here is a simple example that can trigger a segmentation fault. Below, I provide several links containing reproductions of a few peculiar behaviors.
func main() {
for range yieldInts {
defer func() {
log.Println("recover:called")
recover()
}()
}
}
func yieldInts(yield func(int) bool) {
if !yield(0) {
return
}
log.Println("will panic")
panic("stop")
}output:
2025/02/12 14:34:15 will panic
2025/02/12 14:34:15 recover:called
fatal error: panic while printing panic value: type runtime.errorString
[signal SIGSEGV: segmentation violation code=0x1 addr=0x29 pc=0x9e0d613]
...
What did you see happen?
2025/02/12 14:34:15 will panic
2025/02/12 14:34:15 recover:called
fatal error: panic while printing panic value: type runtime.errorString
[signal SIGSEGV: segmentation violation code=0x1 addr=0x29 pc=0x9e0d613]
...
Bizarre Behavior One
Bizarre Behavior two
Bizarre Behavior three
This issue likely arises from the compiler's handling of the stack when transforming the for loop body into a range function.
What did you expect to see?
I hope to observe behavior that aligns exactly with what is described in this official documentation. It should not include those unpredictable and peculiar behaviors that it does not describe.
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