cgo: set alignment to 1 for unions and classes; avoids crash from divide-by-zero

Fixes #4114.

R=golang-dev, iant, rsc, iant, devon.odell
CC=golang-dev
https://golang.org/cl/6553050

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index d16d0202f663e053ae14a3f952e625311295ce82..eee7602307c77f45614121738358808a3e62ad19 100644 (file)
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -1190,11 +1190,12 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
                t.Go = name // publish before recursive calls
                goIdent[name.Name] = name
                switch dt.Kind {
-               case "union", "class":
+               case "class", "union":
                        t.Go = c.Opaque(t.Size)
                        if t.C.Empty() {
                                t.C.Set("typeof(unsigned char[%d])", t.Size)
                        }
+                       t.Align = 1 // TODO: should probably base this on field alignment.
                        typedef[name.Name] = t
                case "struct":
                        g, csyntax, align := c.Struct(dt, pos)