runtime/pprof: incorrect function names for generics functions #64528
Description
Go version
go version devel go1.22-de5b418bea Sat Dec 2 03:15:03 2023 +0000 linux/amd64
What operating system and processor architecture are you using (go env)?
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/korniltsev/.cache/go-build'
GOENV='/home/korniltsev/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/korniltsev/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/korniltsev/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/korniltsev/github/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/korniltsev/github/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.22-de5b418bea Sat Dec 2 03:15:03 2023 +0000'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/korniltsev/github/go/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 -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3732277415=/tmp/go-build -gno-record-gcc-switches'What did you do?
I wrote a test
func genericAllocFunc[T any](n int) []T {
return make([]T, int(n))
}
func profileToString(p *profile.Profile) []string {
var res []string
for _, s := range p.Sample {
var funcs []string
for i := range s.Location {
loc := s.Location[len(s.Location)-1-i]
for _, line := range loc.Line {
funcs = append(funcs, line.Function.Name)
}
}
res = append(res, fmt.Sprintf("%s %v", strings.Join(funcs, ";"), s.Value))
}
return res
}
func TestGenericsHashKeyInPprofBuilder(t *testing.T) {
functionInt := reflect.ValueOf(genericAllocFunc[int]).Pointer()
functionUint64 := reflect.ValueOf(genericAllocFunc[uint64]).Pointer()
rate := int64(524288)
rec := []runtime.MemProfileRecord{
{
AllocBytes: 128, AllocObjects: 1,
FreeBytes: 0, FreeObjects: 0,
Stack0: [32]uintptr{functionInt},
},
{
AllocBytes: 239, AllocObjects: 1,
FreeBytes: 0, FreeObjects: 0,
Stack0: [32]uintptr{functionUint64},
},
}
var buf bytes.Buffer
if err := writeHeapProto(&buf, rec, rate, ""); err != nil {
t.Fatalf("writing profile: %v", err)
}
p, err := profile.Parse(&buf)
if err != nil {
t.Fatalf("profile.Parse: %v", err)
}
actual := profileToString(p)
expected := []string{
"runtime/pprof.genericAllocFunc[int] [4096 524352 4096 524352]",
"runtime/pprof.genericAllocFunc[uint64] [2194 524407 2194 524407]",
}
if !reflect.DeepEqual(actual, expected) {
t.Errorf("profile = %v\nwant = %v", actual, expected)
}
}
What did you expect to see?
I expected the test to pass
What did you see instead?
The test fails.
I suspect the reason is because profileBuilder is using Frame->Function as key for checking if we already emited a function. However for generics functions it has dots there [...], so sometime for different functions with different generics types, the profileBuilder uses wrong functions.
https://github.com/golang/go/blob/de5b418bea70aaf27de1f47e9b5813940d1e15a4/src/runtime/pprof/proto.go#L614C39-L614C39