gc: index bounds tests and fixes

move constant index checking to front end
x[2:1] is a compile-time error now too

R=ken2
CC=golang-dev
https://golang.org/cl/1848056

src/cmd/5g/cgen.c

@@ -605,13 +605,6 @@ agen(Node *n, Node *res)
 				n1.type = types[tptr];
 				n1.xoffset = Array_array;
 				gmove(&n1, &n3);
-			} else
-			if(!debug['B'] && !n->etype) {
-				if(v < 0)
-					yyerror("out of bounds on array");
-				else
-				if(v >= nl->type->bound)
-					yyerror("out of bounds on array");
 			}
 
 			nodconst(&n2, types[tptr], v*w);

src/cmd/5g/ggen.c

@@ -682,6 +682,29 @@ regcmp(const void *va, const void *vb)
 
 static	Prog*	throwpc;
 
+// We're only going to bother inlining if we can
+// convert all the arguments to 32 bits safely.  Can we?
+static int
+fix64(NodeList *nn, int n)
+{
+	NodeList *l;
+	Node *r;
+	int i;
+	
+	l = nn;
+	for(i=0; i<n; i++) {
+		r = l->n->right;
+		if(is64(r->type) && !smallintconst(r)) {
+			if(r->op == OCONV)
+				r = r->left;
+			if(is64(r->type))
+				return 0;
+		}
+		l = l->next;
+	}
+	return 1;
+}
+
 void
 getargs(NodeList *nn, Node *reg, int n)
 {
@@ -813,6 +836,8 @@ cgen_inline(Node *n, Node *res)
 slicearray:
 	if(!sleasy(res))
 		goto no;
+	if(!fix64(n->list, 5))
+		goto no;
 	getargs(n->list, nodes, 5);
 
 	// if(hb[3] > nel[1]) goto throw
@@ -904,6 +929,8 @@ slicearray:
 	return 1;
 
 sliceslice:
+	if(!fix64(n->list, narg))
+		goto no;
 	ntemp.op = OXXX;
 	if(!sleasy(n->list->n->right)) {
 		Node *n0;

src/cmd/5g/gsubr.c

@@ -1841,19 +1841,6 @@ oindex_const:
 		n1.type = types[tptr];
 		n1.xoffset = Array_array;
 		gmove(&n1, reg);
-
-	} else
-	if(!debug['B']) {
-		if(v < 0) {
-			yyerror("out of bounds on array");
-		} else
-		if(o & OPtrto) {
-			if(v >= l->type->type->bound)
-				yyerror("out of bounds on array");
-		} else
-		if(v >= l->type->bound) {
-			yyerror("out of bounds on array");
-		}
 	}
 
 	n2 = *reg;

src/cmd/6g/cgen.c

@@ -418,7 +418,7 @@ void
 agen(Node *n, Node *res)
 {
 	Node *nl, *nr;
-	Node n1, n2, n3, tmp, n4;
+	Node n1, n2, n3, tmp, n4, n5;
 	Prog *p1;
 	uint32 w;
 	uint64 v;
@@ -518,13 +518,12 @@ agen(Node *n, Node *res)
 		if(isconst(nr, CTINT)) {
 			v = mpgetfix(nr->val.u.xval);
 			if(isslice(nl->type)) {
-
 				if(!debug['B'] && !n->etype) {
 					n1 = n3;
 					n1.op = OINDREG;
 					n1.type = types[tptr];
 					n1.xoffset = Array_nel;
-					nodconst(&n2, types[TUINT64], v);
+					nodconst(&n2, types[TUINT32], v);
 					gins(optoas(OCMP, types[TUINT32]), &n1, &n2);
 					p1 = gbranch(optoas(OGT, types[TUINT32]), T);
 					ginscall(panicindex, 0);
@@ -536,13 +535,6 @@ agen(Node *n, Node *res)
 				n1.type = types[tptr];
 				n1.xoffset = Array_array;
 				gmove(&n1, &n3);
-			} else
-			if(!debug['B'] && !n->etype) {
-				if(v < 0)
-					yyerror("out of bounds on array");
-				else
-				if(v >= nl->type->bound)
-					yyerror("out of bounds on array");
 			}
 
 			nodconst(&n2, types[tptr], v*w);
@@ -564,15 +556,28 @@ agen(Node *n, Node *res)
 
 		if(!debug['B'] && !n->etype) {
 			// check bounds
+			n5.op = OXXX;
+			t = types[TUINT32];
 			if(isslice(nl->type)) {
 				n1 = n3;
 				n1.op = OINDREG;
-				n1.type = types[tptr];
+				n1.type = types[TUINT32];
 				n1.xoffset = Array_nel;
-			} else
-				nodconst(&n1, types[TUINT64], nl->type->bound);
-			gins(optoas(OCMP, types[TUINT32]), &n2, &n1);
-			p1 = gbranch(optoas(OLT, types[TUINT32]), T);
+				if(is64(nr->type)) {
+					t = types[TUINT64];
+					regalloc(&n5, t, N);
+					gmove(&n1, &n5);
+					n1 = n5;
+				}
+			} else {
+				if(is64(nr->type))
+					t = types[TUINT64];
+				nodconst(&n1, t, nl->type->bound);
+			}
+			gins(optoas(OCMP, t), &n2, &n1);
+			p1 = gbranch(optoas(OLT, t), T);
+			if(n5.op != OXXX)
+				regfree(&n5);
 			ginscall(panicindex, 0);
 			patch(p1, pc);
 		}

src/cmd/6g/ggen.c

@@ -1115,44 +1115,62 @@ getargs(NodeList *nn, Node *reg, int n)
 void
 cmpandthrow(Node *nl, Node *nr)
 {
-	vlong cl, cr;
+	vlong cl;
 	Prog *p1;
 	int op;
 	Node *c;
+	Type *t;
+	Node n1;
+	
+	if(nl->op == OCONV && is64(nl->type))
+		nl = nl->left;
+	if(nr->op == OCONV && is64(nr->type))
+		nr = nr->left;
 
 	op = OLE;
 	if(smallintconst(nl)) {
 		cl = mpgetfix(nl->val.u.xval);
 		if(cl == 0)
 			return;
-		if(smallintconst(nr)) {
-			cr = mpgetfix(nr->val.u.xval);
-			if(cl > cr) {
-				if(throwpc == nil) {
-					throwpc = pc;
-					ginscall(panicslice, 0);
-				} else
-					patch(gbranch(AJMP, T), throwpc);
-			}
+		if(smallintconst(nr))
 			return;
-		}
-
 		// put the constant on the right
 		op = brrev(op);
 		c = nl;
 		nl = nr;
 		nr = c;
 	}
-
-	gins(optoas(OCMP, types[TUINT32]), nl, nr);
+	if(is64(nr->type) && smallintconst(nr))
+		nr->type = types[TUINT32];
+
+	n1.op = OXXX;
+	t = types[TUINT32];
+	if(is64(nl->type) || is64(nr->type)) {
+		// two 64-bit is just a 64-bit compare,
+		// but one 32 and one 64 needs to copy
+		// the 32 into a register to get the full comparison.
+		t = types[TUINT64];
+		if(!is64(nl->type) && nl->op != OLITERAL) {
+			regalloc(&n1, t, nl);
+			gmove(nl, &n1);
+			nl = &n1;
+		} else if(!is64(nr->type) && nr->op != OLITERAL) {
+			regalloc(&n1, t, nr);
+			gmove(nr, &n1);
+			nr = &n1;
+		}
+	}
+	gins(optoas(OCMP, t), nl, nr);
+	if(n1.op != OXXX)
+		regfree(&n1);
 	if(throwpc == nil) {
-		p1 = gbranch(optoas(op, types[TUINT32]), T);
+		p1 = gbranch(optoas(op, t), T);
 		throwpc = pc;
 		ginscall(panicslice, 0);
 		patch(p1, pc);
 	} else {
 		op = brcom(op);
-		p1 = gbranch(optoas(op, types[TUINT32]), T);
+		p1 = gbranch(optoas(op, t), T);
 		patch(p1, throwpc);
 	}
 }
@@ -1312,6 +1330,7 @@ sliceslice:
 		// if(lb[1] > old.nel[0]) goto throw;
 		n2 = nodes[0];
 		n2.xoffset += Array_nel;
+		n2.type = types[TUINT32];
 		cmpandthrow(&nodes[1], &n2);
 
 		// ret.nel = old.nel[0]-lb[1];
@@ -1331,6 +1350,7 @@ sliceslice:
 		// if(hb[2] > old.cap[0]) goto throw;
 		n2 = nodes[0];
 		n2.xoffset += Array_cap;
+		n2.type = types[TUINT32];
 		cmpandthrow(&nodes[2], &n2);
 
 		// if(lb[1] > hb[2]) goto throw;

src/cmd/6g/gsubr.c

@@ -1716,7 +1716,7 @@ sudoaddable(int as, Node *n, Addr *a)
 	int o, i, w;
 	int oary[10];
 	int64 v;
-	Node n1, n2, n3, *nn, *l, *r;
+	Node n1, n2, n3, n4, *nn, *l, *r;
 	Node *reg, *reg1;
 	Prog *p1;
 	Type *t;
@@ -1836,9 +1836,6 @@ oindex:
 		break;
 	}
 
-//	if(sudoaddable(as, l, a))
-//		goto oindex_sudo;
-
 	cleani += 2;
 	reg = &clean[cleani-1];
 	reg1 = &clean[cleani-2];
@@ -1879,16 +1876,29 @@ oindex:
 
 	// check bounds
 	if(!debug['B'] && !n->etype) {
+		// check bounds
+		n4.op = OXXX;
+		t = types[TUINT32];
 		if(o & ODynam) {
 			n2 = *reg;
 			n2.op = OINDREG;
-			n2.type = types[tptr];
+			n2.type = types[TUINT32];
 			n2.xoffset = Array_nel;
+			if(is64(r->type)) {
+				t = types[TUINT64];
+				regalloc(&n4, t, N);
+				gmove(&n2, &n4);
+				n2 = n4;
+			}
 		} else {
+			if(is64(r->type))
+				t = types[TUINT64];
 			nodconst(&n2, types[TUINT64], l->type->bound);
 		}
-		gins(optoas(OCMP, types[TUINT32]), reg1, &n2);
-		p1 = gbranch(optoas(OLT, types[TUINT32]), T);
+		gins(optoas(OCMP, t), reg1, &n2);
+		p1 = gbranch(optoas(OLT, t), T);
+		if(n4.op != OXXX)
+			regfree(&n4);
 		ginscall(panicindex, 0);
 		patch(p1, pc);
 	}
@@ -1915,15 +1925,6 @@ oindex_const:
 	// can multiply by width statically
 
 	v = mpgetfix(r->val.u.xval);
-	if(!debug['B'] && (o & ODynam) == 0) {
-		// array indexed by a constant bounds check
-		if(v < 0) {
-			yyerror("out of bounds on array");
-		} else
-		if(v >= l->type->bound) {
-			yyerror("out of bounds on array");
-		}
-	}
 
 	if(sudoaddable(as, l, a))
 		goto oindex_const_sudo;

src/cmd/8g/cgen.c

@@ -591,13 +591,6 @@ agen(Node *n, Node *res)
 				n1.type = types[tptr];
 				n1.xoffset = Array_array;
 				gmove(&n1, &n3);
-			} else
-			if(!debug['B'] && !n->etype) {
-				if(v < 0)
-					yyerror("out of bounds on array");
-				else
-				if(v >= nl->type->bound)
-					yyerror("out of bounds on array");
 			}
 
 			nodconst(&n2, types[tptr], v*w);

src/cmd/8g/ggen.c

@@ -789,25 +789,58 @@ regcmp(const void *va, const void *vb)
 
 static	Prog*	throwpc;
 
+// We're only going to bother inlining if we can
+// convert all the arguments to 32 bits safely.  Can we?
+static int
+fix64(NodeList *nn, int n)
+{
+	NodeList *l;
+	Node *r;
+	int i;
+	
+	l = nn;
+	for(i=0; i<n; i++) {
+		r = l->n->right;
+		if(is64(r->type) && !smallintconst(r)) {
+			if(r->op == OCONV)
+				r = r->left;
+			if(is64(r->type))
+				return 0;
+		}
+		l = l->next;
+	}
+	return 1;
+}
+
 void
 getargs(NodeList *nn, Node *reg, int n)
 {
 	NodeList *l;
+	Node *r;
 	int i;
 
 	throwpc = nil;
 
 	l = nn;
 	for(i=0; i<n; i++) {
-		if(!smallintconst(l->n->right) && !isslice(l->n->right->type)) {
+		r = l->n->right;
+		if(is64(r->type)) {
+			if(r->op == OCONV)
+				r = r->left;
+			else if(smallintconst(r))
+				r->type = types[TUINT32];
+			if(is64(r->type))
+				fatal("getargs");
+		}
+		if(!smallintconst(r) && !isslice(r->type)) {
 			if(i < 3)	// AX CX DX
-				nodreg(reg+i, l->n->right->type, D_AX+i);
+				nodreg(reg+i, r->type, D_AX+i);
 			else
 				reg[i].op = OXXX;
-			regalloc(reg+i, l->n->right->type, reg+i);
-			cgen(l->n->right, reg+i);
+			regalloc(reg+i, r->type, reg+i);
+			cgen(r, reg+i);
 		} else
-			reg[i] = *l->n->right;
+			reg[i] = *r;
 		if(reg[i].local != 0)
 			yyerror("local used");
 		reg[i].local = l->n->left->xoffset;
@@ -908,6 +941,8 @@ cgen_inline(Node *n, Node *res)
 slicearray:
 	if(!sleasy(res))
 		goto no;
+	if(!fix64(n->list, 5))
+		goto no;
 	getargs(n->list, nodes, 5);
 
 	// if(hb[3] > nel[1]) goto throw
@@ -990,6 +1025,8 @@ slicearray:
 	return 1;
 
 sliceslice:
+	if(!fix64(n->list, narg))
+		goto no;
 	ntemp.op = OXXX;
 	if(!sleasy(n->list->n->right)) {
 		Node *n0;

src/cmd/gc/builtin.c.boot

@@ -75,9 +75,9 @@ char *runtimeimport =
 	"func \"\".selectdefault (sel *uint8) bool\n"
 	"func \"\".selectgo (sel *uint8)\n"
 	"func \"\".makeslice (typ *uint8, nel int64, cap int64) []any\n"
-	"func \"\".sliceslice1 (old []any, lb int, width int) []any\n"
-	"func \"\".sliceslice (old []any, lb int, hb int, width int) []any\n"
-	"func \"\".slicearray (old *any, nel int, lb int, hb int, width int) []any\n"
+	"func \"\".sliceslice1 (old []any, lb uint64, width uint64) []any\n"
+	"func \"\".sliceslice (old []any, lb uint64, hb uint64, width uint64) []any\n"
+	"func \"\".slicearray (old *any, nel uint64, lb uint64, hb uint64, width uint64) []any\n"
 	"func \"\".closure ()\n"
 	"func \"\".int64div (? int64, ? int64) int64\n"
 	"func \"\".uint64div (? uint64, ? uint64) uint64\n"

src/cmd/gc/const.c

@@ -1092,6 +1092,12 @@ smallintconst(Node *n)
 	case TBOOL:
 	case TPTR32:
 		return 1;
+	case TINT64:
+	case TUINT64:
+		if(mpcmpfixfix(n->val.u.xval, minintval[TINT32]) < 0
+		|| mpcmpfixfix(n->val.u.xval, maxintval[TINT32]) > 0)
+			break;
+		return 1;
 	}
 	return 0;
 }

src/cmd/gc/mparith2.c

@@ -536,7 +536,7 @@ mpgetfix(Mpint *a)
 	vlong v;
 
 	if(a->ovf) {
-		yyerror("ovf in mpgetfix");
+		yyerror("constant overflow");
 		return 0;
 	}
 

src/cmd/gc/runtime.go

@@ -99,9 +99,9 @@ func selectdefault(sel *byte) (selected bool)
 func selectgo(sel *byte)
 
 func makeslice(typ *byte, nel int64, cap int64) (ary []any)
-func sliceslice1(old []any, lb int, width int) (ary []any)
-func sliceslice(old []any, lb int, hb int, width int) (ary []any)
-func slicearray(old *any, nel int, lb int, hb int, width int) (ary []any)
+func sliceslice1(old []any, lb uint64, width uint64) (ary []any)
+func sliceslice(old []any, lb uint64, hb uint64, width uint64) (ary []any)
+func slicearray(old *any, nel uint64, lb uint64, hb uint64, width uint64) (ary []any)
 
 func closure() // has args, but compiler fills in
 

src/cmd/gc/typecheck.c

@@ -561,7 +561,7 @@ reswitch:
 			goto error;
 
 		case TARRAY:
-			defaultlit(&n->right, types[TUINT]);
+			defaultlit(&n->right, T);
 			if(n->right->type != T && !isint[n->right->type->etype])
 				yyerror("non-integer array index %#N", n->right);
 			n->type = t->type;
@@ -635,8 +635,8 @@ reswitch:
 		typecheck(&n->right->left, Erv);
 		typecheck(&n->right->right, Erv);
 		defaultlit(&n->left, T);
-		defaultlit(&n->right->left, types[TUINT]);
-		defaultlit(&n->right->right, types[TUINT]);
+		defaultlit(&n->right->left, T);
+		defaultlit(&n->right->right, T);
 		if(isfixedarray(n->left->type)) {
 			// Insert explicit & before fixed array
 			// so that back end knows to move to heap.

src/cmd/gc/walk.c

@@ -565,6 +565,7 @@ walkexpr(Node **np, NodeList **init)
 	NodeList *ll, *lr, *lpost;
 	Type *t;
 	int et;
+	int64 v, v1, v2, len;
 	int32 lno;
 	Node *n, *fn;
 	char buf[100], *p;
@@ -1023,6 +1024,18 @@ walkexpr(Node **np, NodeList **init)
 		if((1<<(8*n->right->type->width)) <= n->left->type->bound)
 			n->etype = 1;
 
+		// check for static out of bounds
+		if(isconst(n->right, CTINT) && !n->etype) {
+			v = mpgetfix(n->right->val.u.xval);
+			len = 1LL<<60;
+			t = n->left->type;
+			if(t != T && isptr[t->etype])
+				t = t->type;
+			if(isfixedarray(t))
+				len = t->bound;
+			if(v < 0 || v >= (1LL<<31) || v >= len)
+				yyerror("index out of bounds");
+		}
 		goto ret;
 
 	case OINDEXMAP:
@@ -1039,15 +1052,48 @@ walkexpr(Node **np, NodeList **init)
 		goto ret;
 
 	case OSLICE:
+	case OSLICEARR:
 		walkexpr(&n->left, init);
 		n->left = safeexpr(n->left, init);
 		walkexpr(&n->right->left, init);
 		n->right->left = safeexpr(n->right->left, init);
 		walkexpr(&n->right->right, init);
 		n->right->right = safeexpr(n->right->right, init);
+
+		len = 1LL<<60;
+		t = n->left->type;
+		if(t != T && isptr[t->etype])
+			t = t->type;
+		if(isfixedarray(t))
+			len = t->bound;
+
+		// check for static out of bounds
+		// NOTE: v > len not v >= len.
+		v1 = -1;
+		v2 = -1;
+		if(isconst(n->right->left, CTINT)) {
+			v1 = mpgetfix(n->right->left->val.u.xval);
+			if(v1 < 0 || v1 >= (1LL<<31) || v1 > len) {
+				yyerror("slice index out of bounds");
+				v1 = -1;
+			}
+		}
+		if(isconst(n->right->right, CTINT)) {
+			v2 = mpgetfix(n->right->right->val.u.xval);
+			if(v2 < 0 || v2 >= (1LL<<31) || v2 > len) {
+				yyerror("slice index out of bounds");
+				v2 = -1;
+			}
+		}
+		if(v1 >= 0 && v2 >= 0 && v1 > v2)
+			yyerror("inverted slice range");
+		
+		if(n->op == OSLICEARR)
+			goto slicearray;
+
 		// dynamic slice
-		// sliceslice(old []any, lb int, hb int, width int) (ary []any)
-		// sliceslice1(old []any, lb int, width int) (ary []any)
+		// sliceslice(old []any, lb uint64, hb uint64, width uint64) (ary []any)
+		// sliceslice1(old []any, lb uint64, width uint64) (ary []any)
 		t = n->type;
 		if(n->right->right != N) {
 			fn = syslook("sliceslice", 1);
@@ -1055,8 +1101,8 @@ walkexpr(Node **np, NodeList **init)
 			argtype(fn, t->type);			// any-2
 			n = mkcall1(fn, t, init,
 				n->left,
-				conv(n->right->left, types[TINT]),
-				conv(n->right->right, types[TINT]),
+				conv(n->right->left, types[TUINT64]),
+				conv(n->right->right, types[TUINT64]),
 				nodintconst(t->type->width));
 		} else {
 			fn = syslook("sliceslice1", 1);
@@ -1064,20 +1110,14 @@ walkexpr(Node **np, NodeList **init)
 			argtype(fn, t->type);			// any-2
 			n = mkcall1(fn, t, init,
 				n->left,
-				conv(n->right->left, types[TINT]),
+				conv(n->right->left, types[TUINT64]),
 				nodintconst(t->type->width));
 		}
 		goto ret;
 
-	case OSLICEARR:
-		walkexpr(&n->left, init);
-		n->left = safeexpr(n->left, init);
-		walkexpr(&n->right->left, init);
-		n->right->left = safeexpr(n->right->left, init);
-		walkexpr(&n->right->right, init);
-		n->right->right = safeexpr(n->right->right, init);
+	slicearray:
 		// static slice
-		// slicearray(old *any, nel int, lb int, hb int, width int) (ary []any)
+		// slicearray(old *any, uint64 nel, lb uint64, hb uint64, width uint64) (ary []any)
 		t = n->type;
 		fn = syslook("slicearray", 1);
 		argtype(fn, n->left->type);	// any-1
@@ -1085,16 +1125,16 @@ walkexpr(Node **np, NodeList **init)
 		if(n->right->right == N)
 			r = nodintconst(n->left->type->bound);
 		else
-			r = conv(n->right->right, types[TINT]);
+			r = conv(n->right->right, types[TUINT64]);
 		n = mkcall1(fn, t, init,
 			nod(OADDR, n->left, N), nodintconst(n->left->type->bound),
-			conv(n->right->left, types[TINT]),
+			conv(n->right->left, types[TUINT64]),
 			r,
 			nodintconst(t->type->width));
 		goto ret;
 
 	case OCONVSLICE:
-		// slicearray(old *any, nel int, lb int, hb int, width int) (ary []any)
+		// slicearray(old *any, uint64 nel, lb uint64, hb uint64, width uint64) (ary []any)
 		fn = syslook("slicearray", 1);
 		argtype(fn, n->left->type->type);		// any-1
 		argtype(fn, n->type->type);			// any-2

src/pkg/runtime/slice.c

@@ -39,9 +39,9 @@ void
 	}
 }
 
-// sliceslice(old []any, lb int, hb int, width int) (ary []any);
+// sliceslice(old []any, lb uint64, hb uint64, width uint64) (ary []any);
 void
-·sliceslice(Slice old, uint32 lb, uint32 hb, uint32 width, Slice ret)
+·sliceslice(Slice old, uint64 lb, uint64 hb, uint64 width, Slice ret)
 {
 	if(hb > old.cap || lb > hb) {
 		if(debug) {
@@ -86,9 +86,9 @@ void
 	}
 }
 
-// sliceslice1(old []any, lb int, width int) (ary []any);
+// sliceslice1(old []any, lb uint64, width uint64) (ary []any);
 void
-·sliceslice1(Slice old, uint32 lb, uint32 width, Slice ret)
+·sliceslice1(Slice old, uint64 lb, uint64 width, Slice ret)
 {
 	if(lb > old.len) {
 		if(debug) {
@@ -129,9 +129,9 @@ void
 	}
 }
 
-// slicearray(old *any, nel int, lb int, hb int, width int) (ary []any);
+// slicearray(old *any, nel uint64, lb uint64, hb uint64, width uint64) (ary []any);
 void
-·slicearray(byte* old, uint32 nel, uint32 lb, uint32 hb, uint32 width, Slice ret)
+·slicearray(byte* old, uint64 nel, uint64 lb, uint64 hb, uint64 width, Slice ret)
 {
 	if(nel > 0 && old == nil) {
 		// crash if old == nil.

test/index.go

+// $G $D/$F.go && $L $F.$A &&
+// ./$A.out -pass 0 >tmp.go && $G tmp.go && $L -o tmp1.$A tmp.$A && ./tmp1.$A &&
+// ./$A.out -pass 1 >tmp.go && errchk $G -e tmp.go &&
+// ./$A.out -pass 2 >tmp.go && errchk $G -e tmp.go
+// rm -f tmp.go
+
+// Copyright 2010 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.
+
+// Generate test of index and slice bounds checks.
+
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"os"
+)
+
+const prolog = `
+
+package main
+
+import (
+	"runtime"
+)
+
+type quad struct { x, y, z, w int }
+
+const (
+	cj = 11
+	ci int = 12
+	ci32 int32 = 13
+	ci64 int64 = 14
+	ci64big int64 = 1<<31
+	ci64bigger int64 = 1<<32
+	chuge = 1<<100
+
+	cnj = -2
+	cni int = -3
+	cni32 int32 = -4
+	cni64 int64 = -5
+	cni64big int64 = -1<<31
+	cni64bigger int64 = -1<<32
+	cnhuge = -1<<100
+)
+
+var j int = 20
+var i int = 21
+var i32 int32 = 22
+var i64 int64 = 23
+var i64big int64 = 1<<31
+var i64bigger int64 = 1<<32
+var huge uint64 = 1<<64 - 1
+
+var nj int = -10
+var ni int = -11
+var ni32 int32 = -12
+var ni64 int64 = -13
+var ni64big int64 = -1<<31
+var ni64bigger int64 = -1<<32
+var nhuge int64 = -1<<63
+
+var si []int = make([]int, 10)
+var ai [10]int
+var pai *[10]int = &ai
+
+var sq []quad = make([]quad, 10)
+var aq [10]quad
+var paq *[10]quad = &aq
+
+type T struct {
+	si []int
+	ai [10]int
+	pai *[10]int
+	sq []quad
+	aq [10]quad
+	paq *[10]quad
+}
+
+var t = T{si, ai, pai, sq, aq, paq}
+
+var pt = &T{si, ai, pai, sq, aq, paq}
+
+// test that f panics
+func test(f func(), s string) {
+	defer func() {
+		if err := recover(); err == nil {
+			_, file, line, _ := runtime.Caller(2)
+			bug()
+			print(file, ":", line, ": ", s, " did not panic\n")
+		}
+	}()
+	f()
+}
+
+var X interface{}
+func use(y interface{}) {
+	X = y
+}
+
+var didBug = false
+
+func bug() {
+	if !didBug {
+		didBug = true
+		println("BUG")
+	}
+}
+
+func main() {
+`
+
+// Passes:
+//	0 - dynamic checks
+//	1 - static checks of invalid constants (cannot assign to types)
+//	2 - static checks of array bounds
+var pass = flag.Int("pass", 0, "which test (0,1,2)")
+
+func testExpr(b *bufio.Writer, expr string) {
+	if *pass == 0 {
+		fmt.Fprintf(b, "\ttest(func(){use(%s)}, %q)\n", expr, expr)
+	} else {
+		fmt.Fprintf(b, "\tuse(%s)  // ERROR \"index|overflow\"\n", expr)
+	}
+}
+
+func main() {
+	b := bufio.NewWriter(os.Stdout)
+
+	flag.Parse()
+	
+	if *pass == 0 {
+		fmt.Fprint(b, "// $G $D/$F.go && $L $F.$A && ./$A.out\n\n")
+	} else {
+		fmt.Fprint(b, "// errchk $G -e $D/$F.go\n\n")
+	}
+	fmt.Fprint(b, prolog)
+	
+	var choices = [][]string{
+		// Direct value, fetch from struct, fetch from struct pointer.
+		// The last two cases get us to oindex_const_sudo in gsubr.c.
+		[]string{"", "t.", "pt."},
+		
+		// Array, pointer to array, slice.
+		[]string{"a", "pa", "s"},
+
+		// Element is int, element is quad (struct).
+		// This controls whether we end up in gsubr.c (i) or cgen.c (q).
+		[]string{"i", "q"},
+
+		// Variable or constant.
+		[]string{"", "c"},
+
+		// Positive or negative.
+		[]string{"", "n"},
+
+		// Size of index.
+		[]string{"j", "i", "i32", "i64", "i64big", "i64bigger", "huge"},
+	}
+	
+	forall(choices, func(x []string) {
+		p, a, e, c, n, i := x[0], x[1], x[2], x[3], x[4], x[5]
+
+		// Pass: dynamic=0, static=1, 2.
+		// Which cases should be caught statically?
+		// Only constants, obviously.
+		// Beyond that, must be one of these:
+		//	indexing into array or pointer to array
+		//	negative constant
+		//	large constant
+		thisPass := 0
+		if c == "c" && (a == "a" || a == "pa" || n == "n" || i == "i64big" || i == "i64bigger" || i == "huge") {
+			if i == "huge" {
+				// Due to a detail of 6g's internals,
+				// the huge constant errors happen in an
+				// earlier pass than the others and inhibits
+				// the next pass from running.
+				// So run it as a separate check.
+				thisPass = 1
+			} else {
+				thisPass = 2
+			}
+		}
+
+		// Only print the test case if it is appropriate for this pass.
+		if thisPass == *pass {
+			pae := p+a+e
+			cni := c+n+i
+			
+			// Index operation
+			testExpr(b, pae + "[" + cni + "]")
+			
+			// Slice operation.
+			// Low index 0 is a special case in ggen.c
+			// so test both 0 and 1.
+			testExpr(b, pae + "[0:" + cni + "]")
+			testExpr(b, pae + "[1:" + cni + "]")
+			testExpr(b, pae + "[" + cni + ":]")
+			testExpr(b, pae + "[" + cni + ":" + cni + "]")
+		}
+	})
+
+	fmt.Fprintln(b, "}")
+	b.Flush()
+}
+
+func forall(choices [][]string, f func([]string)) {
+	x := make([]string, len(choices))
+	
+	var recurse func(d int)
+	recurse = func(d int) {
+		if d >= len(choices) {
+			f(x)
+			return
+		}
+		for _, x[d] = range choices[d] {
+			recurse(d+1)
+		}
+	}
+	recurse(0)
+}

test/recover2.go

@@ -52,7 +52,9 @@ func test2() {
 
 func test3() {
 	defer mustRecover("slice")
-	println(x[11:9])
+	var lo = 11
+	var hi = 9
+	println(x[lo:hi])
 }
 
 func test4() {