Enable stricter compiler warnings

Test: m apf_run apf_disassembler libapf
Change-Id: I43b975a6afa11f693268317de69967e7774a1c85
diff --git a/Android.bp b/Android.bp
index 6832407..d2185b5 100644
--- a/Android.bp
+++ b/Android.bp
@@ -7,6 +7,12 @@
         "-DAPF_FRAME_HEADER_SIZE=14",
         "-Wall",
         "-Werror",
+        "-Werror=implicit-fallthrough",
+        "-Wnullable-to-nonnull-conversion",
+        "-Wsign-compare",
+        "-Wthread-safety",
+        "-Wunused-parameter",
+        "-Wuninitialized",
     ],
 }
 
diff --git a/apf_run.c b/apf_run.c
index 3f89b13..c915b80 100644
--- a/apf_run.c
+++ b/apf_run.c
@@ -178,7 +178,7 @@
     char* packet = NULL;
     uint8_t* data = NULL;
     uint32_t data_len = 0;
-    int32_t filter_age = 0;
+    uint32_t filter_age = 0;
 
     int opt;
     char *endptr;