gc: fix smaller-than-pointer-sized receivers in interfaces

Fixes #812.

R=ken2
CC=golang-dev
https://golang.org/cl/1904041

src/cmd/5g/gobj.c

@@ -705,7 +705,7 @@ out:
 	p->to.type = D_OREG;
 	p->to.reg = NREG;
 	p->to.name = D_EXTERN;
-	p->to.sym = methodsym(method->sym, ptrto(f->type));
+	p->to.sym = methodsym(method->sym, ptrto(f->type), 0);
 //print("4. %P\n", p);
 
 	pc->as = ARET;	// overwrite AEND

src/cmd/6g/gobj.c

@@ -732,7 +732,7 @@ out:
 	p = pc;
 	gins(AJMP, N, N);
 	p->to.type = D_EXTERN;
-	p->to.sym = methodsym(method->sym, ptrto(f->type));
+	p->to.sym = methodsym(method->sym, ptrto(f->type), 0);
 //print("6. %P\n", p);
 
 	pc->as = ARET;	// overwrite AEND

src/cmd/8g/gobj.c

@@ -739,7 +739,7 @@ out:
 	p = pc;
 	gins(AJMP, N, N);
 	p->to.type = D_EXTERN;
-	p->to.sym = methodsym(method->sym, ptrto(f->type));
+	p->to.sym = methodsym(method->sym, ptrto(f->type), 0);
 //print("6. %P\n", p);
 
 	pc->as = ARET;	// overwrite AEND

src/cmd/gc/dcl.c

@@ -1017,11 +1017,12 @@ functype(Node *this, NodeList *in, NodeList *out)
 }
 
 Sym*
-methodsym(Sym *nsym, Type *t0)
+methodsym(Sym *nsym, Type *t0, int iface)
 {
 	Sym *s;
 	char *p;
 	Type *t;
+	char *suffix;
 
 	t = t0;
 	if(t == T)
@@ -1043,7 +1044,13 @@ methodsym(Sym *nsym, Type *t0)
 	if(t != t0 && t0->sym)
 		t0 = ptrto(t);
 
-	p = smprint("%#hT·%s", t0, nsym->name);
+	suffix = "";
+	if(iface) {
+		dowidth(t0);
+		if(t0->width < types[tptr]->width)
+			suffix = "·i";
+	}
+	p = smprint("%#hT·%s%s", t0, nsym->name, suffix);
 	s = pkglookup(p, s->pkg);
 	free(p);
 	return s;
@@ -1058,7 +1065,7 @@ methodname(Node *n, Type *t)
 {
 	Sym *s;
 
-	s = methodsym(n->sym, t);
+	s = methodsym(n->sym, t, 0);
 	if(s == S)
 		return n;
 	return newname(s);

src/cmd/gc/go.h

@@ -858,7 +858,7 @@ int	isifacemethod(Type *f);
 void	markdcl(void);
 Node*	methodname(Node *n, Type *t);
 Node*	methodname1(Node *n, Node *t);
-Sym*	methodsym(Sym *nsym, Type *t0);
+Sym*	methodsym(Sym *nsym, Type *t0, int iface);
 Node*	newname(Sym *s);
 Type*	newtype(Sym *s);
 Node*	oldname(Sym *s);
@@ -1061,7 +1061,7 @@ void	flusherrors(void);
 void	frame(int context);
 Type*	funcfirst(Iter *s, Type *t);
 Type*	funcnext(Iter *s);
-void	genwrapper(Type *rcvr, Type *method, Sym *newnam);
+void	genwrapper(Type *rcvr, Type *method, Sym *newnam, int iface);
 Type**	getinarg(Type *t);
 Type*	getinargx(Type *t);
 Type**	getoutarg(Type *t);

src/cmd/gc/reflect.c

@@ -183,14 +183,14 @@ methods(Type *t)
 		a = b;
 
 		a->name = method->name;
-		a->isym = methodsym(method, it);
-		a->tsym = methodsym(method, t);
+		a->isym = methodsym(method, it, 1);
+		a->tsym = methodsym(method, t, 0);
 		a->type = methodfunc(f->type, 1);
 		a->mtype = methodfunc(f->type, 0);
 
 		if(!(a->isym->flags & SymSiggen)) {
 			a->isym->flags |= SymSiggen;
-			if(!eqtype(this, it)) {
+			if(!eqtype(this, it) || this->width < types[tptr]->width) {
 				if(oldlist == nil)
 					oldlist = pc;
 				// Is okay to call genwrapper here always,
@@ -201,7 +201,7 @@ methods(Type *t)
 				&& f->embedded && !isifacemethod(f->type))
 					genembedtramp(it, f, a->isym);
 				else
-					genwrapper(it, f, a->isym);
+					genwrapper(it, f, a->isym, 1);
 			}
 		}
 
@@ -214,7 +214,7 @@ methods(Type *t)
 				&& f->embedded && !isifacemethod(f->type))
 					genembedtramp(t, f, a->tsym);
 				else
-					genwrapper(t, f, a->tsym);
+					genwrapper(t, f, a->tsym, 0);
 			}
 		}
 	}

src/cmd/gc/subr.c

@@ -3043,10 +3043,11 @@ structargs(Type **tl, int mustname)
  *	newnam - the eventual mangled name of this function
  */
 void
-genwrapper(Type *rcvr, Type *method, Sym *newnam)
+genwrapper(Type *rcvr, Type *method, Sym *newnam, int iface)
 {
-	Node *this, *fn, *call, *n, *t;
+	Node *this, *fn, *call, *n, *t, *pad;
 	NodeList *l, *args, *in, *out;
+	Type *tpad;
 
 	if(debug['r'])
 		print("genwrapper rcvrtype=%T method=%T newnam=%S\n",
@@ -3062,8 +3063,21 @@ genwrapper(Type *rcvr, Type *method, Sym *newnam)
 
 	fn = nod(ODCLFUNC, N, N);
 	fn->nname = newname(newnam);
-	t = nod(OTFUNC, this, N);
-	t->list = in;
+	t = nod(OTFUNC, N, N);
+	l = list1(this);
+	if(iface && rcvr->width < types[tptr]->width) {
+		// Building method for interface table and receiver
+		// is smaller than the single pointer-sized word
+		// that the interface call will pass in.
+		// Add a dummy padding argument after the
+		// receiver to make up the difference.
+		tpad = typ(TARRAY);
+		tpad->type = types[TUINT8];
+		tpad->bound = types[tptr]->width - rcvr->width;
+		pad = nod(ODCLFIELD, newname(lookup(".pad")), typenod(tpad));
+		l = list(l, pad);
+	}
+	t->list = concat(l, in);
 	t->rlist = out;
 	fn->nname->ntype = t;
 	funchdr(fn);

src/cmd/gc/typecheck.c

@@ -494,7 +494,7 @@ reswitch:
 				goto error;
 			}
 			n->op = ONAME;
-			n->sym = methodsym(sym, l->type);
+			n->sym = methodsym(sym, l->type, 0);
 			n->type = methodfunc(n->type, 1);
 			n->xoffset = 0;
 			getinargx(n->type)->type->type = l->type;	// fix up receiver

test/fixedbugs/bug296.go

@@ -0,0 +1,82 @@
+package main
+
+type I interface {
+	m(a, b, c, d, e, f, g, h byte)
+}
+
+type Int8 int8
+
+func (x Int8) m(a, b, c, d, e, f, g, h byte) {
+	check("Int8", int64(x), 0x01, a, b, c, d, e, f, g, h)
+}
+
+type Uint8 uint8
+
+func (x Uint8) m(a, b, c, d, e, f, g, h byte) {
+	check("Uint8", int64(x), 0x01, a, b, c, d, e, f, g, h)
+}
+
+type Int16 int16
+
+func (x Int16) m(a, b, c, d, e, f, g, h byte) {
+	check("Int16", int64(x), 0x0102, a, b, c, d, e, f, g, h)
+}
+
+type Uint16 uint16
+
+func (x Uint16) m(a, b, c, d, e, f, g, h byte) {
+	check("Uint16", int64(x), 0x0102, a, b, c, d, e, f, g, h)
+}
+
+type Int32 int32
+
+func (x Int32) m(a, b, c, d, e, f, g, h byte) {
+	check("Int32", int64(x), 0x01020304, a, b, c, d, e, f, g, h)
+}
+
+type Uint32 uint32
+
+func (x Uint32) m(a, b, c, d, e, f, g, h byte) {
+	check("Uint32", int64(x), 0x01020304, a, b, c, d, e, f, g, h)
+}
+
+type Int64 int64
+
+func (x Int64) m(a, b, c, d, e, f, g, h byte) {
+	check("Int64", int64(x), 0x0102030405060708, a, b, c, d, e, f, g, h)
+}
+
+type Uint64 uint64
+
+func (x Uint64) m(a, b, c, d, e, f, g, h byte) {
+	check("Uint64", int64(x), 0x0102030405060708, a, b, c, d, e, f, g, h)
+}
+
+var test = []I{
+	Int8(0x01),
+	Uint8(0x01),
+	Int16(0x0102),
+	Uint16(0x0102),
+	Int32(0x01020304),
+	Uint32(0x01020304),
+	Int64(0x0102030405060708),
+	Uint64(0x0102030405060708),
+}
+
+func main() {
+	for _, t := range test {
+		t.m(0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17)
+	}
+}
+
+var bug = false
+
+func check(desc string, have, want int64, a, b, c, d, e, f, g, h byte) {
+	if have != want || a != 0x10 || b != 0x11 || c != 0x12 || d != 0x13 || e != 0x14 || f != 0x15 || g != 0x16 || h != 0x17 {
+		if !bug {
+			bug = true
+			println("BUG")
+		}
+		println(desc, "check", have, want, a, b, c, d, e, f, g, h)
+	}
+}