From da572cc718333a65d7a0f81d6baa106d17ca70c6 Mon Sep 17 00:00:00 2001
From: ToyB-Chan <jasjason0otto@gmail.com>
Date: Wed, 10 Jun 2026 04:10:12 +0200
Subject: [PATCH] =?UTF-8?q?changed=20the=20way=20allocation=20sizes=20are?=
 =?UTF-8?q?=20calculated=20(=E2=98=A0)?=
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---
 minimal_heap_implementation.inl | 32 ++++++++++++++++++--------------
 minimal_heap_test.c             |  6 +++---
 2 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/minimal_heap_implementation.inl b/minimal_heap_implementation.inl
index 5d4fd30..71bf711 100644
--- a/minimal_heap_implementation.inl
+++ b/minimal_heap_implementation.inl
@@ -156,12 +156,13 @@ void* MIHP_Allocate(MIHP_Heap* heap, size_t size)
 			size_t segmentHeaderSize = MIHP_GetHeapAlignedSize(heap, sizeof(MIHP_HeapSegmentHeader));
 			MIHP_HeapSegmentHeader* targetSegment = NULL;
 
-			if (currentSegment->SegmentSize >= 2 * segmentHeaderSize + size + MIHP_GetMinimalPayloadSize(heap))
-				MIHP_SplitHeapSegment(heap, currentSegment, segmentHeaderSize + size, &targetSegment);
-			else if (currentSegment->SegmentSize >= segmentHeaderSize + size)
-				targetSegment = currentSegment;
-			else
-				continue;
+			if (!MIHP_SplitHeapSegment(heap, currentSegment, segmentHeaderSize + size, &targetSegment))
+			{
+				if (currentSegment->SegmentSize >= segmentHeaderSize + size)
+					targetSegment = currentSegment;
+				else
+					continue;
+			}
 
 			targetSegment->OccupiedSize = size;
 			targetSegment->Checksum = MIHP_GenerateHeapSegmentChecksum(heap, targetSegment);
@@ -274,15 +275,13 @@ void* MIHP_Reallocate(MIHP_Heap* heap, void* ptr, size_t newSize)
 		segment->Checksum = MIHP_GenerateHeapSegmentChecksum(heap, segment);
 
 		size_t alignedNewSize = MIHP_GetHeapAlignedSize(heap, newSize);
-		if (segment->SegmentSize > 2 * segmentHeaderSize + alignedNewSize + MIHP_GetMinimalPayloadSize(heap))
-		{
-			size_t newSplitSegmentSize = segment->SegmentSize - segmentHeaderSize - alignedNewSize;
+		size_t newSplitSegmentSize = segment->SegmentSize - segmentHeaderSize - alignedNewSize;
 
-			MIHP_HeapSegmentHeader* newSpittedSegment = NULL;
-			MIHP_SplitHeapSegment(heap, segment, newSplitSegmentSize, &newSpittedSegment);
-			if (newSpittedSegment && newSpittedSegment->NextSegment)
-				MIHP_MergeHeapSegments(heap, newSpittedSegment, newSpittedSegment->NextSegment); // Try directly merging with the adjacent segment
-		}
+		MIHP_HeapSegmentHeader* newSpittedSegment = NULL;
+		MIHP_SplitHeapSegment(heap, segment, newSplitSegmentSize, &newSpittedSegment);
+
+		if (newSpittedSegment && newSpittedSegment->NextSegment)
+			MIHP_MergeHeapSegments(heap, newSpittedSegment, newSpittedSegment->NextSegment); // Try directly merging with the adjacent segment
 
 		MIHP_UnlockHeap(heap);
 		return ptr;
@@ -609,6 +608,8 @@ bool MIHP_SplitHeapSegment(MIHP_Heap* heap, MIHP_HeapSegmentHeader* sourceSegmen
 	MIHP_ASSERT(sourceSegment);
 
 	size_t headerSize = MIHP_GetHeapAlignedSize(heap, sizeof(MIHP_HeapSegmentHeader));
+	newSegmentMinSize = MIHP_MAX(MIHP_GetMinimalPayloadSize(heap) + headerSize, newSegmentMinSize);
+
 	size_t effectiveNewSegmentSize = MIHP_GetHeapAlignedSize(heap, newSegmentMinSize);
 
 	if (sourceSegment->SegmentSize < effectiveNewSegmentSize)
@@ -616,6 +617,9 @@ bool MIHP_SplitHeapSegment(MIHP_Heap* heap, MIHP_HeapSegmentHeader* sourceSegmen
 
 	size_t sourceResultingSegmentSize = sourceSegment->SegmentSize - effectiveNewSegmentSize;
 
+	if (sourceResultingSegmentSize < MIHP_GetMinimalPayloadSize(heap) + headerSize)
+		return false;
+	
 	if (sourceResultingSegmentSize < sourceSegment->OccupiedSize + headerSize)
 		return false;
 
diff --git a/minimal_heap_test.c b/minimal_heap_test.c
index 5eec170..3537976 100644
--- a/minimal_heap_test.c
+++ b/minimal_heap_test.c
@@ -26,7 +26,7 @@ void OnHeapCorruptionDetectedCallback(const MIHP_Heap* heap, MIHP_HeapCorruption
 	__debugbreak();
 }
 
-#define NUM_ALLOCATIONS (4096 * 4096)
+#define NUM_ALLOCATIONS (4096 * 4)
 
 void* myptrs[NUM_ALLOCATIONS] = { 0 };
 
@@ -38,14 +38,14 @@ int main()
 	config.PlatformFreeMemoryFn = FreeMemory;
 	config.OnHeapCorruptionDetectedFn = OnHeapCorruptionDetectedCallback;
 
-	config.HeapValidationMode = MIHP_HVM_None;
+	config.HeapValidationMode = MIHP_HVM_Checksum;
 
 	MIHP_Heap myHeap = { 0 };
 	MIHP_InitializeHeap(&myHeap, config);
 
 	for (int i = 0; i < NUM_ALLOCATIONS; i++)
 	{
-		size_t size = 473 + (i % 5 == 0 ? 854 : 0);
+		size_t size = 565 + (i % 5 == 0 ? 854 : 0);
 #if USE_MALLOC
 		myptrs[i] = malloc(size);
 #else