misc, runtime, test: extra tests and benchmarks for defer

Add a bunch of extra tests and benchmarks for defer, in preparation for new
low-cost (open-coded) implementation of defers (see #34481),

 - New file defer_test.go that tests a bunch more unusual defer scenarios,
   including things that might have problems for open-coded defers.
 - Additions to callers_test.go actually verifying what the stack trace looks like
   for various panic or panic-recover scenarios.
 - Additions to crash_test.go testing several more crash scenarios involving
   recursive panics.
 - New benchmark in runtime_test.go measuring speed of panic-recover
 - New CGo benchmark in cgo_test.go calling from Go to C back to Go that
   shows defer overhead

Updates #34481

Change-Id: I423523f3e05fc0229d4277dd00073289a5526188
Reviewed-on: https://go-review.googlesource.com/c/go/+/197017
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprog/deadlock.go b/src/runtime/testdata/testprog/deadlock.go
index 5f0d120004..9ca0fc344f 100644
--- a/src/runtime/testdata/testprog/deadlock.go
+++ b/src/runtime/testdata/testprog/deadlock.go
@@ -22,6 +22,8 @@ func init() {
 	register("StackOverflow", StackOverflow)
 	register("ThreadExhaustion", ThreadExhaustion)
 	register("RecursivePanic", RecursivePanic)
+	register("RecursivePanic2", RecursivePanic2)
+	register("RecursivePanic3", RecursivePanic3)
 	register("GoexitExit", GoexitExit)
 	register("GoNil", GoNil)
 	register("MainGoroutineID", MainGoroutineID)
@@ -111,6 +113,39 @@ func RecursivePanic() {
 	panic("again")
 }
 
+// Same as RecursivePanic, but do the first recover and the second panic in
+// separate defers, and make sure they are executed in the correct order.
+func RecursivePanic2() {
+	func() {
+		defer func() {
+			fmt.Println(recover())
+		}()
+		var x [8192]byte
+		func(x [8192]byte) {
+			defer func() {
+				panic("second panic")
+			}()
+			defer func() {
+				fmt.Println(recover())
+			}()
+			panic("first panic")
+		}(x)
+	}()
+	panic("third panic")
+}
+
+// Make sure that the first panic finished as a panic, even though the second
+// panic was recovered
+func RecursivePanic3() {
+	defer func() {
+		defer func() {
+			recover()
+		}()
+		panic("second panic")
+	}()
+	panic("first panic")
+}
+
 func GoexitExit() {
 	println("t1")
 	go func() {