cxgo: Convert string sizeof to len. Fixes #88.

Author: dennwc

c_expr.go

@@ -907,11 +907,15 @@ func (g *translator) cSizeofE(x Expr) Expr {
 			return g.newUnaryExpr(UnarySizeof, x)
 		}
 	}
-	switch cUnwrap(x).(type) {
-	case Bool:
-	case BoolExpr:
+	switch x := cUnwrap(x).(type) {
+	case Bool, BoolExpr:
 		// workaround for C bools (they should be reported as int in some cases)
 		return g.SizeofT(g.env.DefIntT(), nil)
+	case StringLit:
+		return &CallExpr{
+			Fun:  FuncIdent{g.env.Go().LenFunc()},
+			Args: []Expr{x},
+		}
 	}
 	return g.SizeofT(x.CType(nil), nil)
 }

literals_test.go

@@ -57,6 +57,23 @@ func foo() {
 	_ = a
 	a = libc.CString("abc")
 }
+`,
+	},
+	{
+		name:     "string len",
+		builtins: true,
+		src: `
+void foo() {
+	int a;
+	a = sizeof("abc");
+}
+`,
+		exp: `
+func foo() {
+	var a int32
+	_ = a
+	a = int32(len("abc"))
+}
 `,
 	},
 	{