runtime, runtime/pprof: add Func.Entry and goroutine labels

src/runtime/pprof/label.go

@@ -0,0 +1,130 @@
+package pprof
+
+// Goroutine labels, as in upstream Go. The label set lives in the
+// context.Context, so nothing here needs the runtime.
+//
+// This is upstream's pre-1.24 form. Go 1.24 moved the label type into
+// internal/runtime/pprof/label, which TinyGo does not have.
+
+import (
+	"context"
+	"fmt"
+	"slices"
+	"strings"
+)
+
+// label is a single key/value pair in a LabelSet.
+type label struct {
+	key   string
+	value string
+}
+
+// LabelSet is a set of labels.
+type LabelSet struct {
+	list []label
+}
+
+// labelContextKey is the type of contextKeys used for profiler labels.
+type labelContextKey struct{}
+
+func labelValue(ctx context.Context) labelMap {
+	labels, _ := ctx.Value(labelContextKey{}).(*labelMap)
+	if labels == nil {
+		return labelMap(nil)
+	}
+	return *labels
+}
+
+// labelMap is the representation of the label set held in the context type.
+type labelMap map[string]string
+
+// String satisfies Stringer and returns key, value pairs in a consistent
+// order.
+func (l *labelMap) String() string {
+	if l == nil {
+		return ""
+	}
+	keyVals := make([]string, 0, len(*l))
+	for k, v := range *l {
+		keyVals = append(keyVals, fmt.Sprintf("%q:%q", k, v))
+	}
+	slices.Sort(keyVals)
+	return "{" + strings.Join(keyVals, ", ") + "}"
+}
+
+// WithLabels returns a new [context.Context] with the given labels added.
+// A label overwrites a prior label with the same key.
+func WithLabels(ctx context.Context, labels LabelSet) context.Context {
+	parentLabels := labelValue(ctx)
+	childLabels := make(labelMap, len(parentLabels))
+	// TODO(matloob): replace the map implementation with something
+	// more efficient so creating a child context WithLabels doesn't need
+	// to clone the map.
+	for k, v := range parentLabels {
+		childLabels[k] = v
+	}
+	for _, label := range labels.list {
+		childLabels[label.key] = label.value
+	}
+	return context.WithValue(ctx, labelContextKey{}, &childLabels)
+}
+
+// Labels takes an even number of strings representing key-value pairs
+// and makes a [LabelSet] containing them.
+// A label overwrites a prior label with the same key.
+// Currently only the CPU and goroutine profiles utilize any labels
+// information.
+// See https://golang.org/issue/23458 for details.
+func Labels(args ...string) LabelSet {
+	if len(args)%2 != 0 {
+		panic("uneven number of arguments to pprof.Labels")
+	}
+	list := make([]label, 0, len(args)/2)
+	for i := 0; i+1 < len(args); i += 2 {
+		list = append(list, label{key: args[i], value: args[i+1]})
+	}
+	return LabelSet{list: list}
+}
+
+// Label returns the value of the label with the given key on ctx, and a boolean indicating
+// whether that label exists.
+func Label(ctx context.Context, key string) (string, bool) {
+	ctxLabels := labelValue(ctx)
+	v, ok := ctxLabels[key]
+	return v, ok
+}
+
+// ForLabels invokes f with each label set on the context.
+// The function f should return true to continue iteration or false to stop iteration early.
+func ForLabels(ctx context.Context, f func(key, value string) bool) {
+	ctxLabels := labelValue(ctx)
+	keys := make([]string, 0, len(ctxLabels))
+	for k := range ctxLabels {
+		keys = append(keys, k)
+	}
+	slices.Sort(keys)
+	for _, k := range keys {
+		if !f(k, ctxLabels[k]) {
+			break
+		}
+	}
+}
+
+// SetGoroutineLabels sets the current goroutine's labels to match ctx.
+//
+// This is a no-op under TinyGo, whose profiler is itself a stub, so nothing
+// would read the labels back. The label API itself travels in the context.
+func SetGoroutineLabels(ctx context.Context) {}
+
+// Do calls f with a copy of the parent context with the given labels added to
+// the parent's label map. Goroutines spawned while executing f will inherit
+// the augmented label-set. Each key/value pair in labels is inserted into the
+// label map in the order provided, overriding any previous value for the same
+// key. The augmented label map will be set for the duration of the call to f
+// and restored once f returns.
+func Do(ctx context.Context, labels LabelSet, f func(context.Context)) {
+	defer SetGoroutineLabels(ctx)
+	ctx = WithLabels(ctx, labels)
+	SetGoroutineLabels(ctx)
+	f(ctx)
+}

src/runtime/stack.go

@@ -15,6 +15,12 @@ func (f *Func) FileLine(pc uintptr) (file string, line int) {
 	return "", 0
 }
 
+// Entry returns the entry address of the function. It is stubbed like the
+// rest of runtime.Func, so that callers such as testify/mock compile.
+func (f *Func) Entry() uintptr {
+	return 0
+}
+
 func Caller(skip int) (pc uintptr, file string, line int, ok bool) {
 	return 0, "", 0, false
 }