Various cleanups of issues caught by clang-tidy

Change-Id: I6e79c121e7c9032cf5053dd31971e719fe76f4b6
diff --git a/build_tests/tcmalloc.cc b/build_tests/tcmalloc.cc
index eb74a65..c1d4429 100644
--- a/build_tests/tcmalloc.cc
+++ b/build_tests/tcmalloc.cc
@@ -1,3 +1,6 @@
 #include <stdlib.h>
 
-int main() { void *big_chunk __attribute__((unused)) = malloc(500000); }
+int main() {
+  void *big_chunk = malloc(500000);
+  free(big_chunk);
+}