runtime: use new frame argument size information

With this CL, I believe the runtime always knows
the frame size during the gc walk. There is no fallback
to "assume entire stack frame of caller" anymore.

R=golang-dev, khr, cshapiro, dvyukov
CC=golang-dev
https://golang.org/cl/11374044

1 files changed, 6 insertions, 1 deletions

diff --git a/src/pkg/runtime/panic.c b/src/pkg/runtime/panic.c
index 8d7d261faf..120f7706e7 100644
--- a/src/pkg/runtime/panic.c
+++ b/src/pkg/runtime/panic.c
@@ -156,9 +156,14 @@ runtime·deferproc(int32 siz, FuncVal *fn, ...)
 // is called again and again until there are no more deferred functions.
 // Cannot split the stack because we reuse the caller's frame to
 // call the deferred function.
+//
+// The ... in the prototype keeps the compiler from declaring
+// an argument frame size. deferreturn is a very special function,
+// and if the runtime ever asks for its frame size, that means
+// the traceback routines are probably broken.
 #pragma textflag 7
 void
-runtime·deferreturn(uintptr arg0)
+runtime·deferreturn(uintptr arg0, ...)
 {
 	Defer *d;
 	byte *argp;