[llvm] 34e8aff - [Support] Recycler: Enforce minimum allocation size (#121425)

[via llvm-commits]

Author: Akshat Oke
Date: 2025-01-06T11:53:56+05:30
New Revision: 34e8aff480dd9cd0372a7c14d13dfca5d3cd1a24

URL: https://github.com/llvm/llvm-project/commit/34e8aff480dd9cd0372a7c14d13dfca5d3cd1a24
DIFF: https://github.com/llvm/llvm-project/commit/34e8aff480dd9cd0372a7c14d13dfca5d3cd1a24.diff

LOG: [Support] Recycler: Enforce minimum allocation size (#121425)

Recycler uses reinterpret_cast to an internal structure of size 8.
Invalid write occurs if Recycler is used for objects with sizes less
than 8.

Added: 
    llvm/unittests/Support/RecyclerTest.cpp

Modified: 
    llvm/include/llvm/Support/Recycler.h
    llvm/unittests/Support/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Support/Recycler.h b/llvm/include/llvm/Support/Recycler.h
index bbd9ae321ae30c..1b9ee2084148d0 100644
--- a/llvm/include/llvm/Support/Recycler.h
+++ b/llvm/include/llvm/Support/Recycler.h
@@ -85,6 +85,8 @@ class Recycler {
                   "Recycler allocation alignment is less than object align!");
     static_assert(sizeof(SubClass) <= Size,
                   "Recycler allocation size is less than object size!");
+    static_assert(Size >= sizeof(FreeNode) &&
+                  "Recycler size must be at least sizeof(FreeNode)");
     return FreeList ? reinterpret_cast<SubClass *>(pop_val())
                     : static_cast<SubClass *>(Allocator.Allocate(Size, Align));
   }

diff  --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
index d64f89847aa8e7..6de81658264420 100644
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -69,6 +69,7 @@ add_llvm_unittest(SupportTests
   PerThreadBumpPtrAllocatorTest.cpp
   ProcessTest.cpp
   ProgramTest.cpp
+  RecyclerTest.cpp
   RegexTest.cpp
   ReverseIterationTest.cpp
   ReplaceFileTest.cpp

diff  --git a/llvm/unittests/Support/RecyclerTest.cpp b/llvm/unittests/Support/RecyclerTest.cpp
new file mode 100644
index 00000000000000..8cd763c0b83f8a
--- /dev/null
+++ b/llvm/unittests/Support/RecyclerTest.cpp
@@ -0,0 +1,46 @@
+//===--- unittest/Support/RecyclerTest.cpp --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Recycler.h"
+#include "llvm/Support/AllocatorBase.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+struct Object1 {
+  char Data[1];
+};
+
+class DecoratedMallocAllocator : public MallocAllocator {
+public:
+  int DeallocCount = 0;
+
+  template <typename T> void Deallocate(T *Ptr) {
+    DeallocCount++;
+    MallocAllocator::Deallocate(Ptr);
+  }
+};
+
+TEST(RecyclerTest, RecycleAllocation) {
+  DecoratedMallocAllocator Allocator;
+  // Recycler needs size to be atleast 8 bytes.
+  Recycler<Object1, 8, 8> R;
+  Object1 *A1 = R.Allocate(Allocator);
+  Object1 *A2 = R.Allocate(Allocator);
+  R.Deallocate(Allocator, A2);
+  Object1 *A3 = R.Allocate(Allocator);
+  EXPECT_EQ(A2, A3); // reuse the deallocated object.
+  R.Deallocate(Allocator, A1);
+  R.Deallocate(Allocator, A3);
+  R.clear(Allocator); // Should deallocate A1 and A3.
+  EXPECT_EQ(Allocator.DeallocCount, 2);
+}
+
+} // end anonymous namespace