gc: zero-width struct, zero-length array fixes

Fixes #1774.
Fixes #2095.
Fixes #2097.

R=ken2
CC=golang-dev
https://golang.org/cl/4826046

src/cmd/5g/cgen.c

@@ -595,9 +595,6 @@ agen(Node *n, Node *res)
 		// i is in &n1 (if not constant)
 		// w is width
 
-		if(w == 0)
-			fatal("index is zero width");
-
 		// constant index
 		if(isconst(nr, CTINT)) {
 			if(isconst(nl, CTSTR))
@@ -683,7 +680,9 @@ agen(Node *n, Node *res)
 			gmove(&n1, &n3);
 		}
 
-		if(w == 1 || w == 2 || w == 4 || w == 8) {
+		if(w == 0) {
+			// nothing to do
+		} else if(w == 1 || w == 2 || w == 4 || w == 8) {
 			memset(&n4, 0, sizeof n4);
 			n4.op = OADDR;
 			n4.left = &n2;

src/cmd/5g/galign.c

@@ -7,6 +7,7 @@
 int	thechar	= '5';
 char*	thestring	= "arm";
 
+vlong MAXWIDTH = (1LL<<32) - 1;
 
 /*
  * go declares several platform-specific type aliases:

src/cmd/6g/cgen.c

@@ -510,9 +510,6 @@ agen(Node *n, Node *res)
 			regfree(&n4);
 		}
 
-		if(w == 0)
-			fatal("index is zero width");
-
 		// constant index
 		if(isconst(nr, CTINT)) {
 			if(isconst(nl, CTSTR))
@@ -600,7 +597,9 @@ agen(Node *n, Node *res)
 			gmove(&n1, &n3);
 		}
 
-		if(w == 1 || w == 2 || w == 4 || w == 8) {
+		if(w == 0) {
+			// nothing to do
+		} else if(w == 1 || w == 2 || w == 4 || w == 8) {
 			p1 = gins(ALEAQ, &n2, &n3);
 			p1->from.scale = w;
 			p1->from.index = p1->from.type;
@@ -608,7 +607,6 @@ agen(Node *n, Node *res)
 		} else {
 			ginscon(optoas(OMUL, t), w, &n2);
 			gins(optoas(OADD, types[tptr]), &n2, &n3);
-			gmove(&n3, res);
 		}
 
 	indexdone:

src/cmd/6g/galign.c

@@ -7,6 +7,7 @@
 int	thechar	= '6';
 char*	thestring	= "amd64";
 
+vlong MAXWIDTH = 1LL<<50;
 
 /*
  * go declares several platform-specific type aliases:

src/cmd/8g/cgen.c

@@ -562,9 +562,6 @@ agen(Node *n, Node *res)
 			regfree(&n4);
 		}
 
-		if(w == 0)
-			fatal("index is zero width");
-
 		// constant index
 		if(isconst(nr, CTINT)) {
 			if(isconst(nl, CTSTR))
@@ -639,7 +636,9 @@ agen(Node *n, Node *res)
 			gmove(&n1, &n3);
 		}
 
-		if(w == 1 || w == 2 || w == 4 || w == 8) {
+		if(w == 0) {
+			// nothing to do
+		} else if(w == 1 || w == 2 || w == 4 || w == 8) {
 			p1 = gins(ALEAL, &n2, &n3);
 			p1->from.scale = w;
 			p1->from.index = p1->from.type;
@@ -648,7 +647,6 @@ agen(Node *n, Node *res)
 			nodconst(&n1, types[TUINT32], w);
 			gins(optoas(OMUL, types[TUINT32]), &n1, &n2);
 			gins(optoas(OADD, types[tptr]), &n2, &n3);
-			gmove(&n3, res);
 		}
 
 	indexdone:

src/cmd/8g/galign.c

@@ -7,6 +7,7 @@
 int	thechar	= '8';
 char*	thestring	= "386";
 
+vlong MAXWIDTH = (1LL<<32) - 1;
 
 /*
  * go declares several platform-specific type aliases:

src/cmd/gc/align.c

@@ -30,14 +30,18 @@ offmod(Type *t)
 	o = 0;
 	for(f=t->type; f!=T; f=f->down) {
 		if(f->etype != TFIELD)
-			fatal("widstruct: not TFIELD: %lT", f);
+			fatal("offmod: not TFIELD: %lT", f);
 		f->width = o;
 		o += widthptr;
+		if(o >= MAXWIDTH) {
+			yyerror("interface too large");
+			o = widthptr;
+		}
 	}
 }
 
-static uint32
+static vlong
-widstruct(Type *t, uint32 o, int flag)
+widstruct(Type *errtype, Type *t, vlong o, int flag)
 {
 	Type *f;
 	int32 w, maxalign;
@@ -69,6 +73,10 @@ widstruct(Type *t, uint32 o, int flag)
 				f->nname->xoffset = o;
 		}
 		o += w;
+		if(o >= MAXWIDTH) {
+			yyerror("type %lT too large", errtype);
+			o = 8;  // small but nonzero
+		}
 	}
 	// final width is rounded
 	if(flag)
@@ -226,10 +234,7 @@ dowidth(Type *t)
 
 			dowidth(t->type);
 			if(t->type->width != 0) {
-				if(tptr == TPTR32)
+				cap = (MAXWIDTH-1) / t->type->width;
-					cap = ((uint32)-1) / t->type->width;
-				else
-					cap = ((uint64)-1) / t->type->width;
 				if(t->bound > cap)
 					yyerror("type %lT larger than address space", t);
 			}
@@ -250,7 +255,7 @@ dowidth(Type *t)
 	case TSTRUCT:
 		if(t->funarg)
 			fatal("dowidth fn struct %T", t);
-		w = widstruct(t, 0, 1);
+		w = widstruct(t, t, 0, 1);
 		break;
 
 	case TFUNC:
@@ -268,9 +273,9 @@ dowidth(Type *t)
 		// function is 3 cated structures;
 		// compute their widths as side-effect.
 		t1 = t->type;
-		w = widstruct(*getthis(t1), 0, 0);
+		w = widstruct(t->type, *getthis(t1), 0, 0);
-		w = widstruct(*getinarg(t1), w, widthptr);
+		w = widstruct(t->type, *getinarg(t1), w, widthptr);
-		w = widstruct(*getoutarg(t1), w, widthptr);
+		w = widstruct(t->type, *getoutarg(t1), w, widthptr);
 		t1->argwid = w;
 		if(w%widthptr)
 			warn("bad type %T %d\n", t1, w);

src/cmd/gc/go.h

@@ -43,9 +43,10 @@ enum
 	AMEMWORD,
 
 	BADWIDTH	= -1000000000,
-	MAXWIDTH	= 1<<30
 };
 
+extern vlong	MAXWIDTH;
+
 /*
  * note this is the representation
  * of the compilers string literals,

src/pkg/runtime/slice.c

@@ -20,7 +20,7 @@ runtime·makeslice(SliceType *t, int64 len, int64 cap, Slice ret)
 {
 	if(len < 0 || (int32)len != len)
 		runtime·panicstring("makeslice: len out of range");
-	if(cap < len || (int32)cap != cap || cap > ((uintptr)-1) / t->elem->size)
+	if(cap < len || (int32)cap != cap || t->elem->size > 0 && cap > ((uintptr)-1) / t->elem->size)
 		runtime·panicstring("makeslice: cap out of range");
 
 	makeslice1(t, len, cap, &ret);

test/fixedbugs/bug273.go

@@ -47,15 +47,6 @@ func bigcap() {
 	g1 = make([]int, 10, big)
 }
 
-const (
-	addrBits = 8*uint(unsafe.Sizeof((*byte)(nil)))
-	sh = addrBits/2 - 2
-)
-var g2 [][1<<sh][1<<sh]byte
-func overflow() {
-	g2 = make([][1<<sh][1<<sh]byte, 64)
-}
-
 var g3 map[int]int
 func badmapcap() {
 	g3 = make(map[int]int, minus1)
@@ -74,6 +65,8 @@ func bigchancap() {
 	g4 = make(chan int, big)
 }
 
+const addrBits = unsafe.Sizeof((*byte)(nil))
+
 var g5 chan [1<<15]byte
 func overflowchan() {
 	if addrBits == 32 {
@@ -92,7 +85,6 @@ func main() {
 	shouldfail(badcap, "badcap")
 	shouldfail(badcap1, "badcap1")
 	shouldfail(bigcap, "bigcap")
-	shouldfail(overflow, "overflow")
 	shouldfail(badmapcap, "badmapcap")
 	shouldfail(bigmapcap, "bigmapcap")
 	shouldfail(badchancap, "badchancap")

test/fixedbugs/bug352.go

@@ -0,0 +1,19 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug352
+
+// Copyright 2011 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.
+
+package main
+
+var x [10][0]byte
+var y = make([]struct{}, 10)
+
+func main() {
+	if &x[1] != &x[2] {
+		println("BUG: bug352 [0]byte")
+	}
+	if &y[1] != &y[2] {
+		println("BUG: bug352 struct{}")
+	}
+}