stacktrace: handle inlining in AppendCallerFrames

Update AppendCallerFrames to take a maximum number
of frames to append. Multiple frames may share a
PC, so it is not enough to just supply the callers
if we want to limit the output. If the supplied
count is negative, return all frames as before.

error.go

@@ -309,7 +309,7 @@ func initStacktrace(e *Error, err error) {
 		for i, frame := range stackTrace {
 			pc[i] = uintptr(frame)
 		}
-		e.stacktrace = stacktrace.AppendCallerFrames(e.stacktrace[:0], pc)
+		e.stacktrace = stacktrace.AppendCallerFrames(e.stacktrace[:0], pc, -1)
 	}
 }
 

stacktrace/stacktrace.go

@@ -27,7 +27,7 @@ func AppendStacktrace(frames []Frame, skip, n int) []Frame {
 		pc = pc[:runtime.Callers(skip+1, pc)]
 	} else {
 		// n is negative, get all frames.
-		n = 0
+		n := 0
 		pc = make([]uintptr, 10)
 		for {
 			n += runtime.Callers(skip+n+1, pc[n:])
@@ -38,19 +38,21 @@ func AppendStacktrace(frames []Frame, skip, n int) []Frame {
 			pc = append(pc, 0)
 		}
 	}
-	return AppendCallerFrames(frames, pc)
+	return AppendCallerFrames(frames, pc, n)
 }
 
-// AppendCallerFrames appends to frames for the PCs in callers,
-// and returns the extended slice.
+// AppendCallerFrames appends to n frames for the PCs in callers,
+// and returns the extended slice. If n is negative, all available
+// frames will be added. Multiple frames may exist for the same
+// caller/PC in the case of function call inlining.
 //
 // See RuntimeFrame for information on what details are included.
-func AppendCallerFrames(frames []Frame, callers []uintptr) []Frame {
+func AppendCallerFrames(frames []Frame, callers []uintptr, n int) []Frame {
 	if len(callers) == 0 {
 		return frames
 	}
 	runtimeFrames := runtime.CallersFrames(callers)
-	for {
+	for i := 0; n < 0 || i < n; i++ {
 		runtimeFrame, more := runtimeFrames.Next()
 		frames = append(frames, RuntimeFrame(runtimeFrame))
 		if !more {