This fixes the majority of the issues but mainly adds get_free_size that exists in the main() and a missing include for memcpy etc

CMakeLists.txt

@@ -38,9 +38,9 @@ endif ()
 
 set(CMAKE_C_STANDARD 11)
 
-add_executable(CustomHeapManager
+add_executable(CustomHeapManager main.c)
-    src/CHM.c include/CHM.h
-    src/main.c
-)
 
-target_include_directories(CustomHeapManager PUBLIC ${PROJECT_SOURCE_DIR}/include)
+if (IS_OS_LINUX)
+    target_link_options(CustomHeapManager PUBLIC)
+elseif (IS_OS_WINDOWS)
+endif ()

include/CHM.h

@@ -1,37 +0,0 @@
-#pragma once
-
-#include <stddef.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <sys/syscall.h>
-
-enum MemMode : unsigned char
-{
-	MEM_MODE_SPEED, // Memory will be allocated more quickly but loses memory efficiency.
-	MEM_MODE_EFFICIENCY, // Memory will be allocated more slowly but gains memory efficiency.
-	MEM_MODE_BALANCED // Memory will be allocated as quickly as possible but also for the sake of memory efficiency.
-};
-
-void set_memory_mode(enum MemMode new_mode);
-
-enum MemMode get_memory_mode();
-
-/// Will find or allocate a memory block appropriately.
-/// @param [in] size The size of the memory block to request.
-/// @returns The allocated memory address on the heap.
-void *malloc(size_t size);
-
-void *realloc(void *ptr, size_t newSize);
-
-/// Will flag the provided memory as free and will defragment other blocks adjacent to it.
-/// @param [in] ptr The memory to flag as free.
-void free(void *ptr);
-
-size_t get_header_size();
-
-/// Will retrieve the current real byte size of the heap.
-/// @returns The size in bytes.
-size_t get_heap_size();
-
-void cleanup_memory();

main.c

@@ -0,0 +1,292 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define ALIGN16(s) (((s) + 15) & ~0x0F)
+#define BLOCK_SIZE sizeof(struct block)
+#define MINIMUM_BLOCK_SIZE (sizeof(struct block) + 16)
+
+/// The memory block's header.
+struct block
+{
+	size_t size;
+	struct block *prev;
+	struct block *next;
+	int free;
+};
+
+struct block *first = NULL;
+struct block *last = NULL;
+
+/// Extends heap memory upwards, towards zero.
+/// @param [in] s The size of the memory needed aligned by 4 bytes.
+/// @returns The new memory block.
+struct block *extend_heap(size_t s)
+{
+    // Ensure the allocated size is at least the minimum block size
+    if (s < MINIMUM_BLOCK_SIZE)
+        s = MINIMUM_BLOCK_SIZE;
+
+    struct block *b = (struct block *)sbrk(0); // Get the current break
+
+    if (sbrk(BLOCK_SIZE + s) == (void *)-1) // Extend the break by s bytes
+        return NULL;
+
+    b->size = s; // Corrected from b->size to b->size
+    b->prev = last;
+    b->next = NULL;
+    b->free =  0;
+
+    if (last)
+        last->next = b;
+
+    last = b;
+
+    return b;
+}
+
+/// Finds the first block that will fit the given size.
+/// @param [in] s The 4 byte aligned size to look for.
+/// @returns The matching available memory block.
+struct block *find_first(size_t s)
+{
+	struct block *current = first;
+	while (current && (!current->free || current->size < s))
+		current = current->next;
+
+	return current;
+}
+
+/// Fragments an existing free memory block into the given size.
+/// @param [in] in The memory block to fragment.
+/// @param [in] s The size of the new memory block.
+/// @returns The new memory block.
+struct block *fragment_block(struct block *in, size_t s)
+{
+	// Calculate the size of the new block, including the block header
+	size_t newBlockSize = s + BLOCK_SIZE;
+
+	// Check if the current block can be split
+	if (in->size <= newBlockSize)
+	{
+		// Cannot split, return the original block
+		return in;
+	}
+
+	// Calculate the size of the remainder block
+	size_t remainderSize = in->size - newBlockSize;
+
+	// Create the new block in the remainder space
+	struct block *newBlock = (struct block *)((char *)(in + 1) + s);
+	newBlock->size = remainderSize;
+	newBlock->prev = in;
+	newBlock->next = in->next;
+	newBlock->free = 1; // Set the new block as free
+
+	// Update the current block to reflect the reduced size
+	in->size = newBlockSize;
+	in->next = newBlock;
+
+	// Insert the new block into the linked list of blocks
+	if (newBlock->next)
+	{
+		newBlock->next->prev = newBlock;
+	}
+
+	return newBlock;
+}
+
+struct block *find_best_fit(size_t s)
+{
+	struct block *current = first;
+	struct block *best_fit = NULL;
+	while (current)
+	{
+		if (current->free && current->size >= s)
+	{
+			if (best_fit && current->size < best_fit->size) // Check for NULL before comparison
+		{
+			{
+				best_fit = current;
+			}
+		}
+		current = current->next;
+	}
+	return best_fit;
+	}
+}
+
+/// Will find or allocate a memory block.
+/// @param [in] size The size of the memory block to request.
+/// @returns The requested memory on the heap.
+/// @todo Fragmenting functionality.
+void *malloc(size_t size)
+{
+	if (size == 0)
+	{
+		return NULL;
+	}
+
+	size = ALIGN16(size);				   // First align the requested size
+	size_t total_size = size + BLOCK_SIZE; // Then add the size of the block header
+
+	struct block *b;
+
+	if (first)
+	{
+		b = find_best_fit(size);
+		if (!b)
+		{
+			b = extend_heap(total_size);
+			if (!b)
+			{
+				return NULL; // Check if heap extension failed
+			}
+		}
+		else if (b->size > total_size + MINIMUM_BLOCK_SIZE)
+		{
+			b = fragment_block(b, size);
+		}
+	}
+	else
+	{
+		b = extend_heap(total_size);
+		if (!b)
+		{
+			return NULL;
+		}
+		first = b;
+	}
+
+	b->free = 0;				   // Mark the block as used
+	return (char *)b + BLOCK_SIZE; // Return a pointer to the usable memory
+}
+
+void *realloc(void *ptr, size_t new_size)
+{
+	if (!ptr)
+	{
+		return malloc(new_size);
+	}
+
+	if (new_size == 0)
+	{
+		free(ptr);
+		return NULL;
+	}
+
+	struct block *b = (struct block *)((char *)ptr - BLOCK_SIZE);
+	if (b->size >= new_size + BLOCK_SIZE)
+	{
+		return ptr; // The block is already big enough
+	}
+
+	void *new_ptr = malloc(new_size);
+	if (!new_ptr)
+	{
+		return NULL; // Allocation failed
+	}
+	memcpy(new_ptr, ptr, b->size - BLOCK_SIZE); // Copy old data to new block, excluding the header size
+	free(ptr);									// Free the old block
+
+	return new_ptr;
+}
+
+/// Will flag the provided memory as free and will defragment other blocks adjacent to it.
+/// @param [in] ptr The memory to flag as free.
+/// @note If all data after the provided memory is free, it will reduce the heap size.
+void my_custom_free(void *ptr)
+{
+    if (!ptr)
+    {
+        return;
+    }
+
+    struct block *b = (struct block *)((char *)ptr - BLOCK_SIZE);
+    if (b->free)
+    {
+        fprintf(stderr, "Double free detected at block %p.\n", ptr);
+        abort(); // Terminate the program immediately due to serious error
+    }
+
+    b->free =  1;
+
+    // Coalesce free blocks
+    while (b->prev && b->prev->free)
+    {
+        // Merge with previous block
+        b->prev->size += BLOCK_SIZE + b->size;
+        b->prev->next = b->next;
+        b = b->prev;
+    }
+
+    // If there is a next block and it's free, merge with it
+    if (b->next && b->next->free)
+    {
+        b->size += BLOCK_SIZE + b->next->size;
+        b->next = b->next->next;
+        if (b->next)
+        {
+            b->next->prev = b;
+        }
+    }
+
+    // After merging, update the 'last' pointer if necessary
+    if (!b->next)
+    {
+        last = b;
+    }
+
+    // Check if we can shrink the heap
+    if (b == last)
+    {
+        // Update 'last' to the previous block or NULL if there's no previous block
+        last = b->prev;
+        if (last)
+        {
+            last->next = NULL;
+        }
+        else
+        {
+            first = NULL;
+        }
+        // Reduce the program break to release the memory
+        sbrk(0 - (b->size + BLOCK_SIZE));
+    }
+}
+
+size_t get_heap_size()
+{
+    size_t total_size =  0;
+    struct block *current = first;
+
+    while (current != NULL)
+    {
+        total_size += current->size;
+        current = current->next;
+    }
+
+    return total_size;
+}
+
+int main()
+{
+    int *a = (int *)malloc(sizeof(int));
+    int *b = (int *)malloc(sizeof(int));
+    int *c = (int *)malloc(sizeof(int)); // Allocate memory for c
+
+    *a =  5;
+    *b =  12;
+
+    printf("Test  1: %i\n", *a);
+    printf("Test  2: %i\n", *b);
+    printf("Heap Size: %zu Bytes\n", get_heap_size()); // Assuming get_heap_size is implemented
+
+    free(a); // Free memory for a
+    free(b); // Free memory for b
+    free(c); // Free memory for c
+
+    return  0;
+}

src/CHM.c

@@ -1,426 +0,0 @@
-#include "CHM.h"
-
-#include <stddef.h>
-#include <stdio.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <sys/syscall.h>
-
-#define ALIGN4(s) (((((s)-1)>>2)<<2)+4)
-#define ALIGN16(s) (((s) + 15) & ~0x0F)
-#define ALIGNMENT 4
-#define BLOCK_SIZE sizeof(struct Block)
-
-/// The memory block's header.
-struct Block
-{
-	size_t size;
-	struct Block *prev;
-	struct Block *next;
-	int free;
-};
-
-enum MemMode mode = MEM_MODE_BALANCED;
-struct Block *first = NULL;
-struct Block *last = NULL;
-
-/// Sets the memory mode for the custom heap manager.
-/// @param [in] new_mode The new mode to use.
-void set_memory_mode(const enum MemMode new_mode)
-{
-	if (new_mode > MEM_MODE_BALANCED)
-	{
-		fprintf(stderr, "The given memory mode, \"%i\", is invalid.", new_mode);
-		return;
-	}
-
-	mode = new_mode;
-}
-
-/// Gets the current memory mode for the custom heap manager.
-/// @returns The current mode.
-enum MemMode get_memory_mode()
-{
-	return mode;
-}
-
-/// Extends heap memory upwards, towards zero.
-/// @param [in] s The size of the memory needed aligned by 4 bytes.
-/// @returns The new memory block.
-struct Block *extend_heap(const size_t s)
-{
-	struct Block* b = (struct Block *)syscall(SYS_brk, NULL);
-
-	if ((void *)syscall(SYS_brk, (char *)(b + 1) + s) == (void *)-1)
-		return NULL;
-
-	b->size = s;
-	b->prev = last;
-	b->next = NULL;
-	b->free = 0;
-
-	if (last)
-		last->next = b;
-
-	last = b;
-
-	return b;
-}
-
-/// Will defragment adjacent memory blocks of the given memory block.
-/// @param [in] in The memory block to defragment for.
-void defragment_adjacent_blocks(struct Block *in)
-{
-	// Go in reverse order to find free memory blocks.
-	while (in->prev && in->prev->free)
-		in = in->prev;
-
-	// Go in forward order to find memory blocks and merge them.
-	while (in->next && in->next->free)
-	{
-		in->size += BLOCK_SIZE + in->next->size;
-		in->next = in->next->next;
-	}
-}
-
-/// Fragments an existing free memory block into the given size.
-/// @param [in] in The memory block to fragment.
-/// @param [in] s The size of the new memory block.
-void fragment_block(struct Block *in, size_t s)
-{
-	// Create the new block in the remainder space
-	struct Block *newBlock = (struct Block *)((char *)(in + 1) + s);
-	newBlock->size = in->size - BLOCK_SIZE - s;
-	newBlock->prev = in;
-	newBlock->next = in->next;
-	newBlock->free = 1;
-
-	// Update the current block to reflect the reduced size
-	in->size = s;
-	in->next = newBlock;
-	in->free = 0;
-}
-
-struct Block *extend_block(struct Block *in, const size_t newSize)
-{
-	if (!in->next)
-	{
-		void *addr = (struct Block *)syscall(SYS_brk, NULL);
-
-		if ((void *)syscall(SYS_brk, (char *)addr + (newSize - in->size)) == (void *)-1)
-			return NULL;
-
-		in->size = newSize;
-
-		return in;
-	}
-
-	size_t totalSize = in->size;
-	struct Block *start = in->prev;
-	struct Block *end = in->next;
-
-	while (start && start->free && totalSize < newSize)
-	{
-		totalSize += BLOCK_SIZE + start->size;
-		if (totalSize >= newSize)
-			break;
-
-		start = in->prev;
-	}
-
-	while (end && end->free && totalSize < newSize)
-	{
-		totalSize += BLOCK_SIZE + end->size;
-		if (totalSize >= newSize)
-			break;
-
-		end = end->next;
-	}
-
-	if (totalSize < newSize || (mode == MEM_MODE_EFFICIENCY && totalSize > newSize))
-		return NULL;
-
-	if (!start)
-		start = in;
-
-	if (!end)
-		end = in;
-
-	struct Block *b = start->next;
-	while (b)
-	{
-		start->size += BLOCK_SIZE + b->size;
-
-		if (b == end)
-			break;
-
-		b = b->next;
-	}
-
-	start->next = end->next;
-	start->free = 0;
-	start->next->prev = start;
-
-	if (!start->next)
-		last = start;
-
-	const size_t remainder = start->size - (BLOCK_SIZE + newSize);
-	if (remainder && !(remainder % ALIGNMENT))
-		fragment_block(start, newSize);
-
-	return start;
-}
-
-/// Finds the first block that will fit the given size.
-/// @param [in] s The memory aligned size to look for.
-/// @returns The matching available memory block.
-struct Block *find_first(const size_t s)
-{
-	const size_t totalSize = BLOCK_SIZE + s;
-	struct Block *current = first;
-	while (current)
-	{
-		if (!current->free || current->size < s)
-		{
-			current = current->next;
-			continue;
-		}
-
-		if (current->size >= s)
-			break;
-
-		current = current->next;
-	}
-
-	return current;
-}
-
-/// Finds the first memory block with more ore equal to the given size and fragments it if necessary.
-/// @param [in] s The memory aligned size to look for.
-/// @returns The matching available memory block.
-struct Block *find_balanced(const size_t s)
-{
-	const size_t totalSize = BLOCK_SIZE + s;
-	struct Block *current = first;
-	while (current)
-	{
-		if (!current->free || current->size < s)
-		{
-			current = current->next;
-			continue;
-		}
-
-		if (current->size == s)
-			break;
-
-		const size_t remainder = current->size - totalSize;
-		if (remainder && !(remainder % ALIGNMENT))
-		{
-			fragment_block(current, s);
-			break;
-		}
-
-		current = current->next;
-	}
-
-	return current;
-}
-
-/// Finds the best fitting memory block with the given size and fragments it if necessary.
-/// @param [in] s The memory aligned size to look for.
-/// @returns The matching available memory block.
-struct Block *find_best_fit(const size_t s)
-{
-	const size_t totalSize = BLOCK_SIZE + s;
-	unsigned char fragment = 0;
-	struct Block *best = NULL;
-	struct Block *current = first;
-
-	while (current)
-	{
-		if (!current->free || current->size < s)
-		{
-			current = current->next;
-			continue;
-		}
-
-		if (current->size == s)
-		{
-			fragment = 0;
-			best = current;
-			break;
-		}
-
-		const size_t remainder = current->size - totalSize;
-		if (best)
-		{
-			if (current->size < best->size && remainder && !(remainder % ALIGNMENT))
-			{
-				fragment = 1;
-				best = current;
-			}
-		}
-		else
-		{
-			if (remainder && !(remainder % ALIGNMENT))
-			{
-				fragment = 1;
-				best = current;
-			}
-		}
-
-		current = current->next;
-	}
-
-	if (best && fragment)
-		fragment_block(best, s);
-
-	return best;
-}
-
-void *malloc(size_t size)
-{
-	if (!size)
-		return NULL;
-
-	size = ALIGN16(size);
-
-	struct Block *b;
-
-	if (first)
-	{
-		switch (mode)
-		{
-			case MEM_MODE_SPEED:
-				b = find_first(size);
-				break;
-			case MEM_MODE_EFFICIENCY:
-				b = find_best_fit(size);
-				break;
-			case MEM_MODE_BALANCED:
-				b = find_balanced(size);
-				break;
-		}
-
-		if (!b)
-		{
-			b = extend_heap(size);
-			if (!b)
-				return NULL;
-		}
-	}
-	else
-	{
-		b = extend_heap(size);
-		if (!b)
-			return NULL;
-
-		first = b;
-		last = b;
-	}
-
-	return b + 1;
-}
-
-void *realloc(void *ptr, size_t newSize)
-{
-	if (!newSize)
-		return NULL;
-
-	if (!ptr)
-		return malloc(newSize);
-
-	newSize = ALIGN16(newSize);
-
-	struct Block *b = (struct Block *)ptr - 1;
-	if (b->free)
-		return NULL;
-
-	if (b->size == newSize)
-		return b + 1;
-
-	const size_t totalSize = BLOCK_SIZE + newSize;
-	const size_t remainder = b->size - totalSize;
-	if (b->size < newSize) // Expand memory block if possible.
-	{
-		if (!extend_block(b, newSize))
-			return NULL;
-
-		return b + 1;
-	}
-	else if (b->size > newSize && remainder && !(remainder % ALIGNMENT)) // Shrink memory block if possible.
-	{
-		fragment_block(b, newSize);
-		return b + 1;
-	}
-
-	return NULL;
-}
-
-void free(void *ptr)
-{
-	if (!ptr)
-		return;
-
-	struct Block *b = (struct Block *)ptr - 1;
-	if (b->free)
-	{
-		fprintf(stderr, "Double free detected for the address %p.\n", ptr);
-		return;
-	}
-
-	b->free = 1;
-
-	if (mode != MEM_MODE_SPEED)
-		defragment_adjacent_blocks(b);
-
-	if (!b->next)
-	{
-		if (!b->prev)
-		{
-			first = NULL;
-			last = NULL;
-		}
-		else
-			last = b;
-
-		syscall(SYS_brk, b);
-	}
-}
-
-size_t get_header_size()
-{
-	return BLOCK_SIZE;
-}
-
-size_t get_heap_size()
-{
-	if (!first || !last)
-		return 0;
-
-	return (char*)last + last->size - (char*)first;
-}
-
-void cleanup_memory()
-{
-	if (!first || !last)
-		return;
-
-	const struct Block *l = last;
-	struct Block *current = first;
-	while (current)
-	{
-		if (!current->free)
-			fprintf(stderr, "Memory at the address %p has not been marked free. Possible memory leak?\n", current + 1);
-
-		if (current == l)
-			break;
-
-		current = current->next;
-	}
-
-	syscall(SYS_brk, first);
-
-	first = NULL;
-	last = NULL;
-}

src/main.c

@@ -1,25 +0,0 @@
-#include "CHM.h"
-
-#include <unistd.h>
-
-int main()
-{
-	set_memory_mode(MEM_MODE_BALANCED);
-
-	int *a = (int *)malloc(sizeof(int));
-	*a = 1;
-	int *b = (int *)malloc(sizeof(int));
-	*b = 2;
-	int *c = (int *)malloc(sizeof(int));
-	*c = 3;
-
-	printf("Heap Size: %zu Bytes\n", get_heap_size());
-
-	free(a);
-	free(b);
-	free(c);
-
-	cleanup_memory();
-
-	return 0;
-}