Appendix to Cmod: Modular Information Hiding and Type-Safe Linking for C

In this section we show that our rules from Figure 2 are sound for MTAL0, assuming no type abstraction or type naming is present. We begin by stating some lemmas about MTAL0 (Figure 4). Lemma 2.1 (Preservation) If ` O1 link O2 ; O then ` O Lemma 2.2 (Associativity of link) If ` (O1 link O2) link O3 ; O then ` O1 link (O2 link O3) ; O. Lemma 2.3 (Commutativity of link) If ` O1 link O2 ; O then ` O2 link O1 ; O. Lemma 2.4 If ∀i, j, 1 ≤ i, j ≤ n, i 6= j . ` Oi link Oj ; Oij and if π is any permutation of {1 . . . n} then ` Oπ(1) link Oπ(2) link . . . link Oπ(n) ; O1...n with ` O1...n.