runtime: only permit SetCgoTraceback to be called once

Accept a duplicate call, but nothing else.

Change-Id: Iec24bf5ddc3b0f0c559ad2158339aca698601743
Reviewed-on: https://go-review.googlesource.com/23692
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go
index 96f154e2131e6c985063e8e0e0aa8c4771ddb250..80a54407b386e33f3db8daf75960887abd590555 100644 (file)
--- a/src/runtime/traceback.go
+++ b/src/runtime/traceback.go
@@ -962,12 +962,21 @@ func isSystemGoroutine(gp *g) bool {
 // traceback function will only be called with the context field set
 // to zero.  If the context function is nil, then calls from Go to C
 // to Go will not show a traceback for the C portion of the call stack.
+//
+// SetCgoTraceback should be called only once, ideally from an init function.
 func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer) {
        if version != 0 {
                panic("unsupported version")
        }
 
+       if cgoTraceback != nil && cgoTraceback != traceback ||
+               cgoContext != nil && cgoContext != context ||
+               cgoSymbolizer != nil && cgoSymbolizer != symbolizer {
+               panic("call SetCgoTraceback only once")
+       }
+
        cgoTraceback = traceback
+       cgoContext = context
        cgoSymbolizer = symbolizer
 
        // The context function is called when a C function calls a Go
@@ -978,6 +987,7 @@ func SetCgoTraceback(version int, traceback, context, symbolizer unsafe.Pointer)
 }
 
 var cgoTraceback unsafe.Pointer
+var cgoContext unsafe.Pointer
 var cgoSymbolizer unsafe.Pointer
 
 // cgoTracebackArg is the type passed to cgoTraceback.