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

src/pkg/runtime/runtime.h

 // 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.
 
 /*
  * basic types
  */
 typedef signed char             int8;
 typedef unsigned char           uint8;
 typedef signed short            int16;
@@ skipping 685 matching lines @@
 {
         int32   siz;
         bool    special;        // not part of defer frame
         byte*   argp;           // where args were copied from
         byte*   pc;
         FuncVal*        fn;
         Defer*  link;
         void*   args[1];        // padded to actual size
 };
 
+// argp used in Defer structs when there is no argp.
+// TODO(rsc): Maybe we could use nil instead, but we've always used -1
+// and I don't want to change this days before the Go 1.3 release.
+#define NoArgs ((byte*)-1)
+
 /*
  * panics
  */
 struct Panic
 {
         Eface   arg;            // argument to panic
         uintptr stackbase;      // g->stackbase in panic
         Panic*  link;           // link to earlier panic
         Defer*  defer;          // current executing defer
         bool    recovered;      // whether this panic is over
@@ skipping 116 matching lines @@
 Slice   runtime·gobytes(byte*, intgo);
 String  runtime·gostringnocopy(byte*);
 String  runtime·gostringw(uint16*);
 void    runtime·initsig(void);
 void    runtime·sigenable(uint32 sig);
 void    runtime·sigdisable(uint32 sig);
 int32   runtime·gotraceback(bool *crash);
 void    runtime·goroutineheader(G*);
 int32   runtime·open(int8*, int32, int32);
 int32   runtime·read(int32, void*, int32);
-int32   runtime·write(int32, void*, int32);
+int32   runtime·write(uintptr, void*, int32); // use uintptr to accommodate windows.
 int32   runtime·close(int32);
 int32   runtime·mincore(void*, uintptr, byte*);
 void    runtime·jmpdefer(FuncVal*, void*);
 void    runtime·exit1(int32);
 void    runtime·ready(G*);
 byte*   runtime·getenv(int8*);
 int32   runtime·atoi(byte*);
 void    runtime·newosproc(M *mp, void *stk);
 void    runtime·mstart(void);
 G*      runtime·malg(int32);
@@ skipping 283 matching lines @@
 extern float64 runtime·neginf;
 extern uint64 ·nan;
 extern uint64 ·posinf;
 extern uint64 ·neginf;
 #define ISNAN(f) ((f) != (f))
 
 enum
 {
         UseSpanType = 1,
 };