gc: bug246

R=ken2
CC=golang-dev
https://golang.org/cl/198057

src/cmd/gc/align.c

@@ -410,6 +410,7 @@ typeinit(void)
 			okforarith[i] = 1;
 			okforadd[i] = 1;
 			okforand[i] = 1;
+			okforconst[i] = 1;
 			issimple[i] = 1;
 			minintval[i] = mal(sizeof(*minintval[i]));
 			maxintval[i] = mal(sizeof(*maxintval[i]));
@@ -419,6 +420,7 @@ typeinit(void)
 			okforcmp[i] = 1;
 			okforadd[i] = 1;
 			okforarith[i] = 1;
+			okforconst[i] = 1;
 			issimple[i] = 1;
 			minfltval[i] = mal(sizeof(*minfltval[i]));
 			maxfltval[i] = mal(sizeof(*maxfltval[i]));
@@ -434,6 +436,9 @@ typeinit(void)
 	okforcap[TARRAY] = 1;
 	okforcap[TCHAN] = 1;
 
+	okforconst[TBOOL] = 1;
+	okforconst[TSTRING] = 1;
+
 	okforlen[TARRAY] = 1;
 	okforlen[TCHAN] = 1;
 	okforlen[TMAP] = 1;

src/cmd/gc/const.c

@@ -93,6 +93,9 @@ convlit1(Node **np, Type *t, int explicit)
 		}
 		return;
 	case OLITERAL:
+		// target is invalid type for a constant?  leave alone.
+		if(!okforconst[t->etype] && n->type->etype != TNIL)
+			return;
 		break;
 	case OLSH:
 	case ORSH:
@@ -105,6 +108,7 @@ convlit1(Node **np, Type *t, int explicit)
 		n->type = t;
 		return;
 	}
+
 	// avoided repeated calculations, errors
 	if(cvttype(n->type, t) == 1) {
 		n->type = t;
@@ -345,7 +349,6 @@ evconst(Node *n)
 	case OANDNOT:
 	case OARRAYBYTESTR:
 	case OCOM:
-	case OCONV:
 	case ODIV:
 	case OEQ:
 	case OGE:
@@ -365,6 +368,12 @@ evconst(Node *n)
 	case OSUB:
 	case OXOR:
 		break;
+	case OCONV:
+		if(n->type == T)
+			return;
+		if(!okforconst[n->type->etype] && n->type->etype != TNIL)
+			return;
+		break;
 	}
 
 	nl = n->left;

src/cmd/gc/go.h

@@ -680,6 +680,7 @@ EXTERN	uchar	okforbool[NTYPE];
 EXTERN	uchar	okforcap[NTYPE];
 EXTERN	uchar	okforlen[NTYPE];
 EXTERN	uchar	okforarith[NTYPE];
+EXTERN	uchar	okforconst[NTYPE];
 EXTERN	uchar*	okfor[OEND];
 EXTERN	uchar	iscmp[OEND];
 

src/cmd/gc/walk.c

@@ -182,7 +182,7 @@ walkdef(Node *n)
 		t = n->type;
 		if(t != T) {
 			convlit(&e, t);
-			if(!isint[t->etype] && !isfloat[t->etype] && t->etype != TSTRING && t->etype != TBOOL)
+			if(!okforconst[t->etype])
 				yyerror("invalid constant type %T", t);
 		}
 		n->val = e->val;

test/fixedbugs/bug246.go

@@ -1,4 +1,4 @@
-// $G $D/$F.go || echo BUG: bug246
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug246
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -10,9 +10,13 @@ import "unsafe"
 
 func main() {
 	// works
-	addr := uintptr(0)
-	_ = (*int)(unsafe.Pointer(addr))
+	addr := uintptr(0x234)
+	x1 := (*int)(unsafe.Pointer(addr))
 
 	// fails
-	_ = (*int)(unsafe.Pointer(uintptr(0)))
+	x2 := (*int)(unsafe.Pointer(uintptr(0x234)))
+	
+	if x1 != x2 {
+		panicln("mismatch", x1, x2)
+	}
 }

test/golden.out

@@ -150,8 +150,3 @@ throw: interface conversion
 panic PC=xxx
 
 == bugs/
-
-=========== bugs/bug246.go
-bugs/bug246.go:17: cannot convert 0 to type unsafe.Pointer
-bugs/bug246.go:17: cannot convert 0 (type uintptr) to type *int in conversion
-BUG: bug246