code review 100870044: runtime: make continuation pc available to stack walk

src/pkg/runtime/cgocall.c

 // Copyright 2009 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include "runtime.h"
 #include "arch_GOARCH.h"
 #include "stack.h"
 #include "cgocall.h"
 #include "race.h"
 #include "../../cmd/ld/textflag.h"
@@ skipping 104 matching lines @@
         m->ncgocall++;
 
         /*
          * Lock g to m to ensure we stay on the same stack if we do a
          * cgo callback. Add entry to defer stack in case of panic.
          */
         runtime·lockOSThread();
         d.fn = &endcgoV;
         d.siz = 0;
         d.link = g->defer;
-        d.argp = (void*)-1;  // unused because unlockm never recovers
+        d.argp = NoArgs;
         d.special = true;
         g->defer = &d;
 ········
         m->ncgo++;
 
         /*
          * Announce we are entering a system call
          * so that the scheduler knows to create another
          * M to run goroutines while we are in the
          * foreign code.
@@ skipping 116 matching lines @@
 
         if(m->needextram) {
                 m->needextram = 0;
                 runtime·newextram();
         }
 
         // Add entry to defer stack in case of panic.
         d.fn = &unwindmf;
         d.siz = 0;
         d.link = g->defer;
-        d.argp = (void*)-1;  // unused because unwindm never recovers
+        d.argp = NoArgs;
         d.special = true;
         g->defer = &d;
 
         if(raceenabled)
                 runtime·raceacquire(&cgosync);
 
         // Invoke callback.
         cb = CBARGS;
         runtime·newstackcall(cb->fn, cb->arg, cb->argsize);
 
@@ skipping 36 matching lines @@
 runtime·cgounimpl(void) // called from (incomplete) assembly
 {
         runtime·throw("runtime: cgo not implemented");
 }
 
 // For cgo-using programs with external linking,
 // export "main" (defined in assembly) so that libc can handle basic
 // C runtime startup and call the Go program as if it were
 // the C main function.
 #pragma cgo_export_static main