Clear up another clangalyzer issue

"The NULL pointer warnings on the return value of
tor_addr_to_in6_addr32() are incorrect. But clang can't work this
out itself due to limited analysis depth. To teach the analyser that
the return value is safe to dereference, I applied tor_assert to the
return value."

Patch from teor.  Part of 13157.

src/common/address.c

@@ -332,8 +332,15 @@ tor_addr_is_internal_(const tor_addr_t *addr, int for_listening,
     iph4 = tor_addr_to_ipv4h(addr);
   } else if (v_family == AF_INET6) {
     if (tor_addr_is_v4(addr)) { /* v4-mapped */
+      uint32_t *addr32 = NULL;
       v_family = AF_INET;
-      iph4 = ntohl(tor_addr_to_in6_addr32(addr)[3]);
+      // Work around an incorrect NULL pointer dereference warning in
+      // "clang --analyze" due to limited analysis depth
+      addr32 = tor_addr_to_in6_addr32(addr);
+      // To improve performance, wrap this assertion in:
+      // #if !defined(__clang_analyzer__) || PARANOIA
+      tor_assert(addr32);
+      iph4 = ntohl(addr32[3]);
     }
   }
 

src/common/address.h

@@ -103,7 +103,18 @@ tor_addr_to_ipv4h(const tor_addr_t *a)
 static INLINE uint32_t
 tor_addr_to_mapped_ipv4h(const tor_addr_t *a)
 {
-  return a->family == AF_INET6 ? ntohl(tor_addr_to_in6_addr32(a)[3]) : 0;
+  if (a->family == AF_INET6) {
+    uint32_t *addr32 = NULL;
+    // Work around an incorrect NULL pointer dereference warning in
+    // "clang --analyze" due to limited analysis depth
+    addr32 = tor_addr_to_in6_addr32(a);
+    // To improve performance, wrap this assertion in:
+    // #if !defined(__clang_analyzer__) || PARANOIA
+    tor_assert(addr32);
+    return ntohl(addr32[3]);
+  } else {
+    return 0;
+  }
 }
 /** Return the address family of <b>a</b>.  Possible values are:
  * AF_INET6, AF_INET, AF_UNSPEC. */

src/test/test_util.c

@@ -2910,6 +2910,9 @@ test_util_spawn_background_fail(void *ptr)
   const int expected_status = PROCESS_STATUS_RUNNING;
 #endif
 
+  memset(expected_out, 0xf0, sizeof(expected_out));
+  memset(code, 0xf0, sizeof(code));
+
   (void)ptr;
 
   tor_snprintf(code, sizeof(code), "%x/%x",