internal/pprof: don't discard allocations called by reflect.Call

The pprof code discards all heap allocations made by runtime
routines. This caused it to discard heap allocations made by functions
called by reflect.Call, as the calls are made via the functions
`runtime.call32`, `runtime.call64`, etc. Fix the profiler to retain
these heap allocations.

Fixes #18077.

Change-Id: I8962d552f1d0b70fc7e6f7b2dbae8d5bdefb0735
Reviewed-on: https://go-review.googlesource.com/33635
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/internal/pprof/profile/legacy_profile.go

@@ -1224,6 +1224,8 @@ var allocSkipRxStr = strings.Join([]string{
 	// Preserve Go runtime frames that appear in the middle/bottom of
 	// the stack.
 	`runtime\.panic`,
+	`runtime\.reflectcall`,
+	`runtime\.call[0-9]*`,
 }, `|`)
 
 var cpuProfilerRxStr = strings.Join([]string{

src/runtime/pprof/mprof_test.go

@@ -7,6 +7,7 @@ package pprof_test
 import (
 	"bytes"
 	"fmt"
+	"reflect"
 	"regexp"
 	"runtime"
 	. "runtime/pprof"
@@ -42,6 +43,17 @@ func allocatePersistent1K() {
 	}
 }
 
+// Allocate transient memory using reflect.Call.
+
+func allocateReflectTransient() {
+	memSink = make([]byte, 2<<20)
+}
+
+func allocateReflect() {
+	rv := reflect.ValueOf(allocateReflectTransient)
+	rv.Call(nil)
+}
+
 var memoryProfilerRun = 0
 
 func TestMemoryProfiler(t *testing.T) {
@@ -61,6 +73,7 @@ func TestMemoryProfiler(t *testing.T) {
 	allocateTransient1M()
 	allocateTransient2M()
 	allocatePersistent1K()
+	allocateReflect()
 	memSink = nil
 
 	runtime.GC() // materialize stats
@@ -73,18 +86,22 @@ func TestMemoryProfiler(t *testing.T) {
 
 	tests := []string{
 		fmt.Sprintf(`%v: %v \[%v: %v\] @ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+
-#	0x[0-9,a-f]+	runtime/pprof_test\.allocatePersistent1K\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test\.go:40
-#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test\.go:63
+#	0x[0-9,a-f]+	runtime/pprof_test\.allocatePersistent1K\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test\.go:41
+#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test\.go:75
 `, 32*memoryProfilerRun, 1024*memoryProfilerRun, 32*memoryProfilerRun, 1024*memoryProfilerRun),
 
 		fmt.Sprintf(`0: 0 \[%v: %v\] @ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+
-#	0x[0-9,a-f]+	runtime/pprof_test\.allocateTransient1M\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:21
-#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:61
+#	0x[0-9,a-f]+	runtime/pprof_test\.allocateTransient1M\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:22
+#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:73
 `, (1<<10)*memoryProfilerRun, (1<<20)*memoryProfilerRun),
 
 		fmt.Sprintf(`0: 0 \[%v: %v\] @ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+ 0x[0-9,a-f]+
-#	0x[0-9,a-f]+	runtime/pprof_test\.allocateTransient2M\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:27
-#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:62
+#	0x[0-9,a-f]+	runtime/pprof_test\.allocateTransient2M\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:28
+#	0x[0-9,a-f]+	runtime/pprof_test\.TestMemoryProfiler\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:74
+`, memoryProfilerRun, (2<<20)*memoryProfilerRun),
+
+		fmt.Sprintf(`0: 0 \[%v: %v\] @( 0x[0-9,a-f]+)+
+#	0x[0-9,a-f]+	runtime/pprof_test\.allocateReflectTransient\+0x[0-9,a-f]+	.*/runtime/pprof/mprof_test.go:49
 `, memoryProfilerRun, (2<<20)*memoryProfilerRun),
 	}