gc: add panic and recover (still unimplemented in runtime)

main semantic change is to enforce single argument to panic.

runtime: change to 1-argument panic.
use String method on argument if it has one.

R=ken2, r
CC=golang-dev
https://golang.org/cl/812043

src/cmd/gc/align.c

@@ -542,6 +542,7 @@ typeinit(void)
 	/* types used in front end */
 	// types[TNIL] got set early in lexinit
 	types[TIDEAL] = typ(TIDEAL);
+	types[TINTER] = typ(TINTER);
 
 	/* simple aliases */
 	simtype[TMAP] = tptr;

src/cmd/gc/builtin.c.boot

@@ -4,7 +4,8 @@ char *runtimeimport =
 	"func \"\".throwindex ()\n"
 	"func \"\".throwreturn ()\n"
 	"func \"\".throwinit ()\n"
-	"func \"\".panicl ()\n"
+	"func \"\".panic (? interface { })\n"
+	"func \"\".recover () interface { }\n"
 	"func \"\".printbool (? bool)\n"
 	"func \"\".printfloat (? float64)\n"
 	"func \"\".printint (? int64)\n"

src/cmd/gc/go.h

@@ -379,6 +379,7 @@ enum
 	OPANIC, OPRINT, OPRINTN,
 	OSEND, OSENDNB,
 	OSLICE, OSLICEARR, OSLICESTR,
+	ORECOVER,
 	ORECV,
 	ORUNESTR,
 	OSELRECV,

src/cmd/gc/lex.c

@@ -1309,6 +1309,7 @@ static	struct
 	"print",	LNAME,		Txxx,		OPRINT,
 	"println",	LNAME,		Txxx,		OPRINTN,
 	"real",		LNAME,		Txxx,		OREAL,
+	"recover",	LNAME,		Txxx,		ORECOVER,
 
 	"notwithstanding",		LIGNORE,	Txxx,		OXXX,
 	"thetruthofthematter",		LIGNORE,	Txxx,		OXXX,

src/cmd/gc/runtime.go

@@ -14,7 +14,9 @@ func mal(int32) *any
 func throwindex()
 func throwreturn()
 func throwinit()
-func panicl()
+
+func panic(interface{})
+func recover() interface{}
 
 func printbool(bool)
 func printfloat(float64)

src/cmd/gc/typecheck.c

@@ -1012,13 +1012,31 @@ reswitch:
 		n->type = ptrto(t);
 		goto ret;
 
-	case OPANIC:
 	case OPRINT:
 	case OPRINTN:
 		ok |= Etop;
 		typechecklist(n->list, Erv);
 		goto ret;
 
+	case OPANIC:
+		ok |= Etop;
+		if(onearg(n) < 0)
+			goto error;
+		typecheck(&n->left, Erv);
+		defaultlit(&n->left, types[TINTER]);
+		if(n->left->type == T)
+			goto error;
+		goto ret;
+	
+	case ORECOVER:
+		ok |= Erv|Etop;
+		if(n->list != nil) {
+			yyerror("too many arguments to recover");
+			goto error;
+		}
+		n->type = types[TINTER];
+		goto ret;
+
 	case OCLOSURE:
 		ok |= Erv;
 		typecheckclosure(n);

src/cmd/gc/walk.c

@@ -425,7 +425,6 @@ walkstmt(Node **np)
 		switch(n->left->op) {
 		case OPRINT:
 		case OPRINTN:
-		case OPANIC:
 			walkexprlist(n->left->list, &n->ninit);
 			n->left = walkprint(n->left, &n->ninit, 1);
 			break;
@@ -623,11 +622,18 @@ walkexpr(Node **np, NodeList **init)
 
 	case OPRINT:
 	case OPRINTN:
-	case OPANIC:
 		walkexprlist(n->list, init);
 		n = walkprint(n, init, 0);
 		goto ret;
 
+	case OPANIC:
+		n = mkcall("panic", T, init, n->left);
+		goto ret;
+
+	case ORECOVER:
+		n = mkcall("recover", n->type, init);
+		goto ret;
+
 	case OLITERAL:
 		n->addable = 1;
 		goto ret;

src/pkg/runtime/386/asm.s

@@ -369,6 +369,19 @@ TEXT stackcheck(SB), 7, $0
 	INT	$3
 	RET
 
+// callString(f, arg, out)
+// call Go f(arg), which returns a string, and store in out
+TEXT callString(SB), 7, $24
+	MOVL	arg+4(FP), BX
+	MOVL	f+0(FP), CX
+	MOVL	BX, 0(SP)
+	CALL	*CX
+	MOVL	out+8(FP), DI
+	LEAL	4(SP), SI
+	MOVSL
+	MOVSL
+	MOVSL
+	RET
 
 GLOBL m0(SB), $1024
 GLOBL g0(SB), $1024

src/pkg/runtime/amd64/asm.s

@@ -311,3 +311,16 @@ TEXT stackcheck(SB), 7, $0
 	INT	$3
 	RET
 
+// callString(f, arg, out)
+// call Go f(arg), which returns a string, and store in out
+TEXT callString(SB), 7, $24
+	MOVQ	arg+8(FP), BX
+	MOVQ	f+0(FP), CX
+	MOVQ	BX, 0(SP)
+	CALL	*CX
+	MOVQ	out+16(FP), DI
+	LEAQ	8(SP), SI
+	MOVSQ
+	MOVSQ
+	RET
+

src/pkg/runtime/arm/asm.s

@@ -264,3 +264,18 @@ TEXT abort(SB),7,$0
 	MOVW	$0, R0
 	MOVW	(R0), R1
 
+// callString(f, arg, out)
+// call Go f(arg), which returns a string, and store in out
+TEXT callString(SB), 7, $24
+	MOVW	arg+4(FP), R1
+	MOVW	f+0(FP), R0
+	MOVW	R1, 0(SP)
+	BL	R0
+	MOVW	4(SP), R1
+	MOVW	8(SP), R2
+	MOVW	12(SP), R3
+	MOVW	out+8(FP), R0
+	MOVW	R1, 0(R0)
+	MOVW	R2, 4(R0)
+	MOVW	R3, 8(R0)
+	RET

src/pkg/runtime/print.c

@@ -3,6 +3,7 @@
 // license that can be found in the LICENSE file.
 
 #include "runtime.h"
+#include "type.h"
 
 //static Lock debuglock;
 
@@ -150,7 +151,7 @@ vprintf(int8 *s, byte *arg)
 			·printhex(*(uint64*)arg);
 			break;
 		case '!':
-			·panicl(-1);
+			panic(-1);
 		}
 		arg = narg;
 		lp = p+1;
@@ -347,3 +348,68 @@ void
 {
 	write(fd, "\n", 1);
 }
+
+// print an empty interface, for use by panic.
+// this could be arbitrarily complex in general,
+// so we pick off only a few important cases:
+// int, string, and values with a String() string method.
+void
+printany(Eface e)
+{
+	int32 i;
+	FuncType *ft;
+	Method *m;
+	String s;
+	Type *rt;
+	UncommonType *x;
+
+	if(e.type == nil) {
+		write(fd, "nil", 3);
+		return;
+	}
+
+	if((x=e.type->x) != nil) {
+		for(i=0; i<x->mhdr.len; i++) {
+			// Look for String() string method.
+			m = &x->m[i];
+			if(m->name->len == 6 &&
+			   mcmp(m->name->str, (byte*)"String", 6) == 0 &&
+			   // Found String; check method signature for func() string.
+			   m->mtyp->kind == KindFunc &&
+			   (ft = (FuncType*)m->mtyp)->in.len == 0 &&
+			   ft->out.len == 1 &&
+			   // Found single output.  Is it string?
+			   // Only base types have name != nil but pkgPath == nil.
+			   (rt = *(Type**)ft->out.array)->kind == KindString &&
+			   rt->x != nil &&
+			   rt->x->name != nil && rt->x->pkgPath == nil) {
+				// Found the method!
+				// Have to use assembly to call it
+				// and save the return value.
+				callString(m->ifn, e.data, &s);
+				·printstring(s);
+				return;
+			}
+		}
+	}
+
+	switch(e.type->kind & ~KindNoPointers) {
+	case KindInt:
+		mcpy((byte*)&i, (byte*)&e.data, sizeof(i));
+		·printint(i);
+		break;
+
+	case KindString:
+		·printstring(*(String*)e.data);
+		break;
+
+	default:
+		// Could print the other numeric types,
+		// but that's overkill: good panics have
+		// a string method anyway.
+		·printstring(*e.type->string);
+		write(fd, "(???)", 5);
+		break;
+	}
+
+}

src/pkg/runtime/runtime.c

@@ -20,7 +20,7 @@ gotraceback(void)
 }
 
 void
-·panicl(int32 lno)
+panic(int32 unused)
 {
 	uint8 *sp;
 
@@ -31,16 +31,25 @@ void
 	}
 	panicking++;
 
-	printf("\npanic PC=%X\n", (uint64)(uintptr)&lno);
-	sp = (uint8*)&lno;
+	printf("\npanic PC=%X\n", (uint64)(uintptr)&unused);
+	sp = (uint8*)&unused;
 	if(gotraceback()){
-		traceback(·getcallerpc(&lno), sp, g);
+		traceback(·getcallerpc(&unused), sp, g);
 		tracebackothers(g);
 	}
 	breakpoint();  // so we can grab it in a debugger
 	exit(2);
 }
 
+void
+·panic(Eface e)
+{
+	fd = 2;
+	printf("panic: ");
+	printany(e);
+	panic(0);
+}
+
 void
 ·throwindex(void)
 {
@@ -70,7 +79,7 @@ throw(int8 *s)
 {
 	fd = 2;
 	printf("throw: %s\n", s);
-	·panicl(-1);
+	panic(-1);
 	*(int32*)0 = 0;	// not reached
 	exit(1);	// even more not reached
 }

src/pkg/runtime/runtime.h

@@ -344,6 +344,7 @@ int32	charntorune(int32*, uint8*, int32);
 /*
  * very low level c-called
  */
+void	callString(void(*fn)(void), void *arg, String *out);
 void	gogo(Gobuf*, uintptr);
 void	gogocall(Gobuf*, void(*)(void));
 uintptr	gosave(Gobuf*);
@@ -354,6 +355,7 @@ void*	getu(void);
 void	throw(int8*);
 uint32	rnd(uint32, uint32);
 void	prints(int8*);
+void	printany(Eface);
 void	printf(int8*, ...);
 byte*	mchr(byte*, byte, byte*);
 void	mcpy(byte*, byte*, uint32);
@@ -510,7 +512,7 @@ void	runtime_printuint(uint64);
 void	runtime_printhex(uint64);
 void	runtime_printslice(Slice);
 void	runtime_printcomplex(Complex128);
-void	·panicl(int32);
+void	panic(int32);
 void	reflect·call(byte*, byte*, uint32);
 
 /*