Fix several compiler warnings.

Change-Id: I55caa50a5937442734f4fcbdb4edf1c70f335bf8
diff --git a/libc/bionic/tmpfile.cpp b/libc/bionic/tmpfile.cpp
index ad58a92..b97cc6c 100644
--- a/libc/bionic/tmpfile.cpp
+++ b/libc/bionic/tmpfile.cpp
@@ -57,7 +57,7 @@
 static FILE* __tmpfile_dir(const char* tmp_dir) {
   char buf[PATH_MAX];
   int path_length = snprintf(buf, sizeof(buf), "%s/tmp.XXXXXXXXXX", tmp_dir);
-  if (path_length >= sizeof(buf)) {
+  if (path_length >= static_cast<int>(sizeof(buf))) {
     return NULL;
   }
 
diff --git a/libc/upstream-netbsd/extern.h b/libc/upstream-netbsd/extern.h
index 942e237..616becd 100644
--- a/libc/upstream-netbsd/extern.h
+++ b/libc/upstream-netbsd/extern.h
@@ -17,6 +17,12 @@
 #ifndef _BIONIC_NETBSD_EXTERN_H_included
 #define _BIONIC_NETBSD_EXTERN_H_included
 
-// Placeholder.
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+const char* __strsignal(int, char*, size_t);
+
+__END_DECLS
 
 #endif
diff --git a/tests/stubs_test.cpp b/tests/stubs_test.cpp
index d2d0ad8..9daaa22 100644
--- a/tests/stubs_test.cpp
+++ b/tests/stubs_test.cpp
@@ -34,7 +34,7 @@
   TYPE_APP
 } uid_type_t;
 
-static void check_getpwnam(const char* username, int uid, uid_type_t uid_type) {
+static void check_getpwnam(const char* username, uid_t uid, uid_type_t uid_type) {
   errno = 0;
   passwd* pwd = getpwuid(uid);
   ASSERT_TRUE(pwd != NULL);