Add David's overflow test (it passes). Fixes #195

c++/src/capnp/encoding-test.c++

@@ -591,6 +591,25 @@ TEST(Encoding, SetListToEmpty) {
 #undef CHECK_EMPTY_NONNULL
 }
 
+#if CAPNP_EXPENSIVE_TESTS
+TEST(Encoding, LongList) {
+  // This test allocates 512MB of contiguous memory and takes several seconds, so we usually don't
+  // run it. It is run before release, though.
+
+  MallocMessageBuilder builder;
+
+  auto root = builder.initRoot<TestAllTypes>();
+  uint length = 1 << 27;
+  auto list = root.initUInt64List(length);
+  for (uint ii = 0; ii < length; ++ii) {
+    list.set(ii, ii);
+  }
+  for (uint ii = 0; ii < length; ++ii) {
+    ASSERT_EQ(list[ii], ii);
+  }
+}
+#endif
+
 // =======================================================================================
 
 TEST(Encoding, ListUpgrade) {

super-test.sh

@@ -219,7 +219,8 @@ done
 # because GCC warns about code that I know is OK.  Disable sign-compare because I've fixed more
 # sign-compare warnings than probably all other warnings combined and I've never seen it flag a
 # real problem. Disable unused parameters because it's stupidly noisy and never a real problem.
-export CXXFLAGS="-O2 -DDEBUG -Wall -Wextra -Werror -Wno-strict-aliasing -Wno-sign-compare -Wno-unused-parameter"
+# Enable expensive release-gating tests.
+export CXXFLAGS="-O2 -DDEBUG -Wall -Wextra -Werror -Wno-strict-aliasing -Wno-sign-compare -Wno-unused-parameter -DCAPNP_EXPENSIVE_TESTS=1"
 
 STAGING=$PWD/tmp-staging