runtime: more detailed panic traces, line number work

Follow morestack, so that crashes during a stack split
give complete traces.  Also mark stack segment boundaries
as an aid to debugging.

Correct various line number bugs with yet another attempt
at interpreting the pc/ln table.  This one has a chance at
being correct, because I based it on reading src/cmd/ld/lib.c
instead of on reading the documentation.

Fixes #1138.
Fixes #1430.
Fixes #1461.

throw: runtime: split stack overflow

runtime.throw+0x3e /home/rsc/g/go2/src/pkg/runtime/runtime.c:78
        runtime.throw(0x81880af, 0xf75c8b18)
runtime.newstack+0xad /home/rsc/g/go2/src/pkg/runtime/proc.c:728
        runtime.newstack()
runtime.morestack+0x4f /home/rsc/g/go2/src/pkg/runtime/386/asm.s:184
        runtime.morestack()
----- morestack called from stack: -----
runtime.new+0x1a /home/rsc/g/go2/src/pkg/runtime/malloc.c:288
        runtime.new(0x1, 0x0, 0x0)
gongo.makeBoard+0x33 /tmp/Gongo/gongo_robot_test.go:344
        gongo.makeBoard(0x809d238, 0x1, 0xf76092c8, 0x1)
----- stack segment boundary -----
gongo.checkEasyScore+0xcc /tmp/Gongo/gongo_robot_test.go:287
        gongo.checkEasyScore(0xf764b710, 0x0, 0x809d238, 0x1)
gongo.TestEasyScore+0x8c /tmp/Gongo/gongo_robot_test.go:255
        gongo.TestEasyScore(0xf764b710, 0x818a990)
testing.tRunner+0x2f /home/rsc/g/go2/src/pkg/testing/testing.go:132
        testing.tRunner(0xf764b710, 0xf763b5dc, 0x0)
runtime.goexit /home/rsc/g/go2/src/pkg/runtime/proc.c:149
        runtime.goexit()

R=ken2, r
CC=golang-dev
https://golang.org/cl/4000053

1 files changed, 10 insertions, 2 deletions

diff --git a/src/pkg/runtime/runtime.c b/src/pkg/runtime/runtime.c
index 284b1e4585..e3a20d48af 100644
--- a/src/pkg/runtime/runtime.c
+++ b/src/pkg/runtime/runtime.c
@@ -528,14 +528,22 @@ void
 runtime·Caller(int32 skip, uintptr retpc, String retfile, int32 retline, bool retbool)
 {
 	Func *f;
+	uintptr pc;
 
-	if(runtime·callers(1+skip, &retpc, 1) == 0 || (f = runtime·findfunc(retpc-1)) == nil) {
+	if(runtime·callers(1+skip, &retpc, 1) == 0) {
 		retfile = runtime·emptystring;
 		retline = 0;
 		retbool = false;
+	} else if((f = runtime·findfunc(retpc)) == nil) {
+		retfile = runtime·emptystring;
+		retline = 0;
+		retbool = true;  // have retpc at least
 	} else {
 		retfile = f->src;
-		retline = runtime·funcline(f, retpc-1);
+		pc = retpc;
+		if(pc > f->entry)
+			pc--;
+		retline = runtime·funcline(f, pc);
 		retbool = true;
 	}
 	FLUSH(&retfile);