runtime: simplify stack traces

Make the stack traces more readable for new
Go programmers while preserving their utility for old hands.

- Change status number [4] to string.
- Elide frames in runtime package (internal details).
- Swap file:line and arguments.
- Drop 'created by' for main goroutine.
- Show goroutines in order of allocation:
  implies main goroutine first if nothing else.

There is no option to get the extra frames back.
Uncomment 'return 1' at the bottom of symtab.c.

$ 6.out
throw: all goroutines are asleep - deadlock!

goroutine 1 [chan send]:
main.main()
       /Users/rsc/g/go/src/pkg/runtime/x.go:22 +0x8a

goroutine 2 [select (no cases)]:
main.sel()
       /Users/rsc/g/go/src/pkg/runtime/x.go:11 +0x18
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:19 +0x23

goroutine 3 [chan receive]:
main.recv(0xf8400010a0, 0x0)
       /Users/rsc/g/go/src/pkg/runtime/x.go:15 +0x2e
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:20 +0x50

goroutine 4 [chan receive (nil chan)]:
main.recv(0x0, 0x0)
       /Users/rsc/g/go/src/pkg/runtime/x.go:15 +0x2e
created by main.main
       /Users/rsc/g/go/src/pkg/runtime/x.go:21 +0x66
$

$ 6.out index
panic: runtime error: index out of range

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:25 +0xb9
$

$ 6.out nil
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x22ca]

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:28 +0x211
$

$ 6.out panic
panic: panic

goroutine 1 [running]:
main.main()
        /Users/rsc/g/go/src/pkg/runtime/x.go:30 +0x101
$

R=golang-dev, qyzhai, n13m3y3r, r
CC=golang-dev
https://golang.org/cl/4907048

1 files changed, 4 insertions, 0 deletions

diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index bea8636a9f..1e52d76ad0 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -199,6 +199,7 @@ struct	G
 	int16	status;
 	int32	goid;
 	uint32	selgen;		// valid sudog pointer
+	int8*	waitreason;	// if status==Gwaiting
 	G*	schedlink;
 	bool	readyonstop;
 	bool	ispanic;
@@ -384,6 +385,7 @@ struct Panic
 extern	Alg	runtime·algarray[Amax];
 extern	String	runtime·emptystring;
 G*	runtime·allg;
+G*	runtime·lastg;
 M*	runtime·allm;
 extern	int32	runtime·gomaxprocs;
 extern	bool	runtime·singleproc;
@@ -434,6 +436,7 @@ String	runtime·gostringnocopy(byte*);
 String	runtime·gostringw(uint16*);
 void	runtime·initsig(int32);
 int32	runtime·gotraceback(void);
+void	runtime·goroutineheader(G*);
 void	runtime·traceback(uint8 *pc, uint8 *sp, uint8 *lr, G* gp);
 void	runtime·tracebackothers(G*);
 int32	runtime·write(int32, void*, int32);
@@ -631,6 +634,7 @@ void	runtime·chansend(ChanType*, Hchan*, void*, bool*);
 void	runtime·chanrecv(ChanType*, Hchan*, void*, bool*, bool*);
 int32	runtime·chanlen(Hchan*);
 int32	runtime·chancap(Hchan*);
+bool	runtime·showframe(Func*);
 
 void	runtime·ifaceE2I(struct InterfaceType*, Eface, Iface*);