runtime: fix TestSehUnwind

The various TestSehUnwind tests recently started to fail due an
unrelated refactor (in CL 698098) that made the stack frames to
not match the expected pattern. This CL updates the tests to
be more robust to such changes.

Fixes #75467

Change-Id: I7950332bb6ca54e4bf693d13e2490b3d9d901dde
Reviewed-on: https://go-review.googlesource.com/c/go/+/703779
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Auto-Submit: Quim Muntal <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: qmuntal

src/runtime/runtime-seh_windows_test.go

@@ -65,14 +65,20 @@ func TestSehLookupFunctionEntry(t *testing.T) {
 	}
 }
 
-func sehCallers() []uintptr {
-	// We don't need a real context,
-	// RtlVirtualUnwind just needs a context with
-	// valid a pc, sp and fp (aka bp).
+//go:noinline
+func newCtx() *windows.Context {
 	var ctx windows.Context
 	ctx.SetPC(sys.GetCallerPC())
 	ctx.SetSP(sys.GetCallerSP())
 	ctx.SetFP(runtime.GetCallerFp())
+	return &ctx
+}
+
+func sehCallers() []uintptr {
+	// We don't need a real context,
+	// RtlVirtualUnwind just needs a context with
+	// valid a pc, sp and fp (aka bp).
+	ctx := newCtx()
 
 	pcs := make([]uintptr, 15)
 	var base, frame uintptr
@@ -84,7 +90,7 @@ func sehCallers() []uintptr {
 		}
 		pcs[i] = ctx.PC()
 		n++
-		windows.RtlVirtualUnwind(0, base, ctx.PC(), fn, unsafe.Pointer(&ctx), nil, &frame, nil)
+		windows.RtlVirtualUnwind(0, base, ctx.PC(), fn, unsafe.Pointer(ctx), nil, &frame, nil)
 	}
 	return pcs[:n]
 }
@@ -120,6 +126,9 @@ func testSehCallersEqual(t *testing.T, pcs []uintptr, want []string) {
 			// These functions are skipped as they appear inconsistently depending
 			// whether inlining is on or off.
 			continue
+		case "runtime_test.sehCallers":
+			// This is an artifact of the implementation of sehCallers.
+			continue
 		}
 		got = append(got, name)
 	}