Change AlignedType to have a void* array member so that swisstable backing arrays end up in the pointer-containing partition for heap partitioning.

PiperOrigin-RevId: 834392373
Change-Id: I46c840995f68f96cdce10f7d3f3c7c43885a5ff8

Author: ezbr

absl/container/BUILD.bazel

@@ -429,6 +429,7 @@ cc_test(
     deps = [
         ":container_memory",
         ":test_instance_tracker",
+        "//absl/base:config",
         "//absl/base:no_destructor",
         "//absl/meta:type_traits",
         "//absl/strings",

absl/container/CMakeLists.txt

@@ -484,6 +484,7 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
+    absl::config
     absl::container_memory
     absl::no_destructor
     absl::strings

absl/container/internal/container_memory.h

@@ -44,7 +44,12 @@ ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
 template <size_t Alignment>
-struct alignas(Alignment) AlignedType {};
+struct alignas(Alignment) AlignedType {
+  // When alignment is sufficient for the allocated memory to store pointers,
+  // include a pointer member so that swisstable backing arrays end up in the
+  // pointer-containing partition for heap partitioning.
+  std::conditional_t<(Alignment < alignof(void*)), char, void*> pointer;
+};
 
 // Allocates at least n bytes aligned to the specified alignment.
 // Alignment must be a power of 2. It must be positive.

absl/container/internal/container_memory_test.cc

@@ -25,6 +25,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/base/config.h"
 #include "absl/base/no_destructor.h"
 #include "absl/container/internal/test_instance_tracker.h"
 #include "absl/meta/type_traits.h"
@@ -42,6 +43,16 @@ using ::testing::ElementsAre;
 using ::testing::Gt;
 using ::testing::Pair;
 
+#if ABSL_HAVE_BUILTIN(__builtin_infer_alloc_token)
+TEST(Memory, AlignedTypeAllocToken) {
+#if defined(__wasm__)
+  GTEST_SKIP() << "Fails on wasm due to lack of heap partitioning support.";
+#endif
+  EXPECT_GT(__builtin_infer_alloc_token(sizeof(AlignedType<alignof(void*)>)),
+            __builtin_infer_alloc_token(sizeof(int)));
+}
+#endif
+
 TEST(Memory, AlignmentLargerThanBase) {
   std::allocator<int8_t> alloc;
   void* mem = Allocate<2>(&alloc, 3);