[compiler-rt] [scudo] Added test fixture for cache tests. (PR #102230)

[Christopher Ferris via llvm-commits]

================
@@ -265,3 +265,101 @@ TEST_F(MapAllocatorWithReleaseTest, SecondaryThreadsRace) {
   Allocator->getStats(&Str);
   Str.output();
 }
+
+struct MapAllocatorCacheTest : public Test {
+  static constexpr scudo::u32 UnmappedMarker = 0xDEADBEEF;
+
+  static void testUnmapCallback(scudo::MemMapT &MemMap) {
+    scudo::u32 *Ptr = reinterpret_cast<scudo::u32 *>(MemMap.getBase());
+    *Ptr = UnmappedMarker;
+  }
+
+  using SecondaryConfig = scudo::SecondaryConfig<TestConfig>;
+  using CacheConfig = SecondaryConfig::CacheConfig;
+  using CacheT = scudo::MapAllocatorCache<CacheConfig, testUnmapCallback>;
+
+  std::unique_ptr<CacheT> Cache = std::make_unique<CacheT>();
+
+  const scudo::uptr PageSize = scudo::getPageSizeCached();
+  // The current test allocation size is set to the minimum size
+  // needed for the scudo allocator to fall back to the secondary allocator
+  static constexpr scudo::uptr TestAllocSize =
+      CacheConfig::getDefaultMaxEntrySize();
+
+  scudo::Options Options = getOptionsForConfig<SecondaryConfig>();
+
+  void SetUp() override { Cache->init(/*ReleaseToOsInterval=*/-1); }
+
+  void TearDown() override { Cache->unmapTestOnly(); }
+
+  scudo::MemMapT allocate(scudo::uptr Size) {
+    scudo::uptr MapSize = scudo::roundUp(Size, PageSize);
+    scudo::ReservedMemoryT ReservedMemory;
+    CHECK(ReservedMemory.create(0U, MapSize, nullptr, MAP_ALLOWNOMEM));
+
+    scudo::MemMapT MemMap = ReservedMemory.dispatch(
+        ReservedMemory.getBase(), ReservedMemory.getCapacity());
+    MemMap.remap(MemMap.getBase(), MemMap.getCapacity(), "scudo:test",
+                 MAP_RESIZABLE | MAP_ALLOWNOMEM);
+    return MemMap;
+  }
+
+  void fillCacheWithSameSizeBlocks(std::vector<scudo::MemMapT> &MemMaps,
+                                   scudo::uptr NumEntries, scudo::uptr Size) {
+    for (scudo::uptr I = 0; I < NumEntries; I++) {
+      MemMaps.emplace_back(allocate(Size));
+      scudo::MemMapT &MemMap = MemMaps[I];
----------------
cferris1000 wrote:

This is a small nit, but you could replace this with:

auto &MemMap = MemMaps.back();

Since the type is in the header, I think it's not going to confuse people about the type, so no need to be explicit. But that's just  my opinion.

https://github.com/llvm/llvm-project/pull/102230