libc.obj: fixes and optimizations for allocator && add new samples to sh build

fix: in `__mem_MERGE_MEM_NODES` `base->free = base->size`, its wrong.
forgot to set size for new block
optimization: add `__last_mem_node`. usually  its node with max free space among other nodes. firstly `malloc` try find space in it.
update(fix and optimizations) `realloc`.
now sdltest is working!

programs/develop/ktcc/trunk/libc.obj/samples/build_all.sh

@@ -23,5 +23,7 @@ cp     clayer/logo.png /tmp0/1/tcc_samples/logo.png
 ../tcc defgen.c -o /tmp0/1/tcc_samples/defgen
 ../tcc pipe.c -o /tmp0/1/tcc_samples/pipe
 ../tcc futex.c -o /tmp0/1/tcc_samples/futex
+../tcc malloc_test.c -o /tmp0/1/tcc_samples/malloc_test
+../tcc atexit_test.c -o /tmp0/1/tcc_samples/atexit_test
 "/sys/File managers/Eolite" /tmp0/1/tcc_samples
 exit

programs/develop/ktcc/trunk/libc.obj/samples/malloc_test.c

@@ -16,11 +16,16 @@
     } while (0)
 
 // c behind a and b
-#define IN_RANGE(a, b, c) (a > c && c > b)
+#define IN_RANGE(a, b, c, len) ((a > c && c > b) || ((a > c + len && c + len > b)))
 
 bool test_malloc_basic_allocation()
 {
-    return malloc(sizeof(int));
+    void* ptr = malloc(sizeof(int));
+
+    if (ptr)
+        free(ptr);
+
+    return ptr;
 }
 bool test_malloc_zero_bytes()
 {
@@ -29,24 +34,25 @@ bool test_malloc_zero_bytes()
 
 bool test_malloc_multiple_allocations()
 {
-    void* ptr[1024];
+    void* ptr[512];
 
     for (int i = 1; i < sizeof(ptr) / sizeof(*ptr); i++) {
         ptr[i] = malloc(i);
         if (ptr[i] == NULL) {
-            printf("fail alloc %d bytes\n", i);
             return false;
         }
     }
     for (int i = 1; i < sizeof(ptr) / sizeof(*ptr); i++) {
-        for (int j = i + 1; j < sizeof(ptr) / sizeof(*ptr) - i - 1; j++) {
+        for (int j = 1; j < sizeof(ptr) / sizeof(*ptr); j++) {
+            if (i != j) {
                 if (ptr[i] == ptr[j]) {
                     printf("ptrs[%d] == ptrs[%d].\n", i, j);
                     return false;
                 } else if (IN_RANGE(
-                           GET_MEM_NODE_HEADER(ptr[i])->size + (char*)GET_MEM_NODE_HEADER(ptr[i]),
+                               (char*)GET_MEM_NODE_HEADER(ptr[i]) + GET_MEM_NODE_HEADER(ptr[i])->size,
-                           (char*)ptr[i],
+                               (char*)GET_MEM_NODE_HEADER(ptr[i]),
-                           (char*)GET_MEM_NODE_HEADER(ptr[j]))) {
+                               (char*)GET_MEM_NODE_HEADER(ptr[j]),
+                               GET_MEM_NODE_HEADER(ptr[j])->size)) {
                     printf("node %p in node %p", GET_MEM_NODE_HEADER(ptr[i]), GET_MEM_NODE_HEADER(ptr[j]));
                     // additional info
                     printf("node %p\nsize:%p\nfree:%p\nnext: %p\nlast: %p\n", GET_MEM_NODE_HEADER(ptr[i]), GET_MEM_NODE_HEADER(ptr[i])->size, GET_MEM_NODE_HEADER(ptr[i])->free, GET_MEM_NODE_HEADER(ptr[i])->next, GET_MEM_NODE_HEADER(ptr[i])->last);
@@ -55,11 +61,19 @@ bool test_malloc_multiple_allocations()
                 }
             }
         }
+    }
+
+    for (int i = 1; i < sizeof(ptr) / sizeof(*ptr); i++) {
+        free(ptr[i]);
+    }
 
     return true;
 }
 bool test_malloc_data_integrity()
 {
+    const char* As = "AAA";
+    const char* Cs = "CCC";
+
     char* A = (char*)malloc(10);
     char* B = (char*)malloc(10);
     char* C = (char*)malloc(10);
@@ -72,18 +86,18 @@ bool test_malloc_data_integrity()
         return false;
     }
 
-    strcpy(A, "AAA");
+    strcpy(A, As);
-    strcpy(C, "CCC");
+    strcpy(C, Cs);
 
     free(B);
 
-    if (strcmp(A, "AAA") != 0) {
+    if (strcmp(A, As) != 0) {
         printf("A data is broken after free(B). A = '%s'\n", A);
         free(A);
         free(C);
         return false;
     }
-    if (strcmp(C, "CCC") != 0) {
+    if (strcmp(C, Cs) != 0) {
         printf("C data is broken after free(B). C = '%s'\n", C);
         free(A);
         free(C);
@@ -96,7 +110,12 @@ bool test_malloc_data_integrity()
 }
 bool test_malloc_large_allocation()
 {
-    return malloc(1024 * 1024 * 8); // alloc 4mb
+    void* ptr = malloc(1024 * 1024 * 16); // alloc 16mb
+
+    if (ptr)
+        free(ptr);
+
+    return ptr;
 }
 bool test_malloc_allocation_and_free()
 {
@@ -104,6 +123,160 @@ bool test_malloc_allocation_and_free()
     return true;
 }
 
+void fill_buffer(void *ptr, size_t size, unsigned char pattern) {
+    if (ptr) {
+        memset(ptr, pattern, size);
+    }
+}
+
+bool check_buffer(void *ptr, size_t size, unsigned char pattern) {
+    if (!ptr) {
+        return false; // Нельзя проверить NULL
+    }
+    unsigned char *byte_ptr = (unsigned char *)ptr;
+    for (size_t i = 0; i < size; ++i) {
+        if (byte_ptr[i] != pattern) {
+            fprintf(stderr, "Ошибка: Байт %zu не соответствует паттерну. Ожидалось %02X, получено %02X\n",
+                    i, pattern, byte_ptr[i]);
+            return false;
+        }
+    }
+    return true;
+}
+
+bool test_realloc_basic_grow() {
+    size_t old_size = 10;
+    size_t new_size = 20;
+    int *ptr = (int *)malloc(old_size * sizeof(int));
+
+    if (ptr == NULL) {
+        return false;
+    }
+    fill_buffer(ptr, old_size * sizeof(int), 0xAA);
+
+    int *new_ptr = (int *)realloc(ptr, new_size * sizeof(int));
+
+    if (new_ptr == NULL) {
+        free(ptr); // Оригинальный блок все еще действителен
+        return false;
+    }
+
+    // Проверяем, что старые данные сохранились
+    if (!check_buffer(new_ptr, old_size * sizeof(int), 0xAA)) {
+        free(new_ptr);
+        return false;
+    }
+
+    // Проверяем, что новый участок доступен для записи
+    fill_buffer(new_ptr + old_size, (new_size - old_size) * sizeof(int), 0xBB);
+    if (!check_buffer(new_ptr + old_size, (new_size - old_size) * sizeof(int), 0xBB)) {
+        free(new_ptr);
+        return false;
+    }
+
+    free(new_ptr);
+    return true;
+}
+
+bool test_realloc_basic_shrink() {
+    size_t old_size = 20;
+    size_t new_size = 10;
+    int *ptr = (int *)malloc(old_size * sizeof(int));
+
+    if (ptr == NULL) {
+        return false;
+    }
+    fill_buffer(ptr, old_size * sizeof(int), 0xCC);
+
+    int *new_ptr = (int *)realloc(ptr, new_size * sizeof(int));
+
+    if (new_ptr == NULL) {
+        free(ptr);
+        return false;
+    }
+
+    if (!check_buffer(new_ptr, new_size * sizeof(int), 0xCC)) {
+        free(new_ptr);
+        return false;
+    }
+
+    free(new_ptr);
+    return true;
+}
+
+bool test_realloc_same_size() {
+    size_t size = 15;
+    int *ptr = (int *)malloc(size * sizeof(int));
+
+    if (ptr == NULL) {
+        return false;
+    }
+    fill_buffer(ptr, size * sizeof(int), 0xDD);
+
+    int *new_ptr = (int *)realloc(ptr, size * sizeof(int));
+
+    if (new_ptr == NULL) {
+        free(ptr);
+        return false;
+    }
+
+    // Проверяем, что данные сохранились
+    if (!check_buffer(new_ptr, size * sizeof(int), 0xDD)) {
+        free(new_ptr);
+        return false;
+    }
+
+    free(new_ptr);
+    
+    return true;
+}
+
+bool test_realloc_null_ptr() {
+    size_t size = 25;
+    void *ptr = realloc(NULL, size);
+
+    if (ptr == NULL) {
+        return false;
+    }
+    
+    // Проверяем, что память доступна
+    fill_buffer(ptr, size, 0xEE);
+    if (!check_buffer(ptr, size, 0xEE)) {
+        free(ptr);
+        return false;
+    }
+
+    free(ptr);
+    
+    return true;
+}
+
+bool test_realloc_to_zero_size() {
+    size_t old_size = 30;
+    void *ptr = malloc(old_size);
+
+    if (ptr == NULL) {
+        return false;
+    }
+    fill_buffer(ptr, old_size, 0xFF);
+
+    void *new_ptr = realloc(ptr, 0);
+
+    // Стандарт C11 (7.22.3.5) говорит, что realloc(ptr, 0) может вернуть NULL
+    // или указатель, который можно передать free().
+    // Если возвращается NULL, оригинальный указатель ptr все еще действителен и должен быть освобожден.
+    // Если возвращается не-NULL, оригинальный ptr недействителен, а новый ptr должен быть освобожден.
+    if (new_ptr == NULL) {
+        printf("realloc(ptr, 0) return NULL.\n");
+        free(ptr); // Освобождаем оригинальный ptr
+    } else {
+        printf("realloc(ptr, 0) return: %p.\n", new_ptr);
+        free(new_ptr); // Освобождаем новый ptr
+    }
+    return true;
+}
+
+
 int main()
 {
     RUN_TEST(test_malloc_basic_allocation);
@@ -112,6 +285,12 @@ int main()
     RUN_TEST(test_malloc_data_integrity);
     RUN_TEST(test_malloc_large_allocation);
     RUN_TEST(test_malloc_basic_allocation);
+    RUN_TEST(test_malloc_allocation_and_free);
+    RUN_TEST(test_realloc_basic_grow);
+    RUN_TEST(test_realloc_basic_shrink);
+    RUN_TEST(test_realloc_same_size);
+    RUN_TEST(test_realloc_null_ptr);
+    RUN_TEST(test_realloc_to_zero_size);
 
     return 0;
 }

programs/develop/ktcc/trunk/libc.obj/source/Tupfile.lua

@@ -2,13 +2,6 @@ if tup.getconfig("NO_TCC") ~= "" then
     return
 end
 
-function AddPrefix(prefix, t)
-    for i, v in pairs(t) do
-        t[i] = prefix .. v
-    end
-    return t
-end
-
 CC = "kos32-tcc"
 
 CFLAGS = " -r -nostdinc -nostdlib -DGNUC -D_BUILD_LIBC -Wall -Werror"
@@ -43,6 +36,10 @@ GAS_SRC = {
     "string/memmove.s",
 }
 
+FASM_SRC = {
+    "crt/crt0.asm",
+}
+
 LIBC_OBJS = { "libc.c" }
 
 tup.append_table(LIBC_OBJS, tup.foreach_rule(GAS_SRC, "as --32 %f -o %o", "%B.o"))
@@ -50,8 +47,4 @@ tup.append_table(LIBC_OBJS, tup.foreach_rule(GAS_SRC, "as --32 %f -o %o", "%B.o"
 tup.rule(LIBC_OBJS, CC .. CFLAGS .. INCLUDES .. " %f -o %o " .. " && strip %o --strip-unneeded ", "libc.o")
 tup.rule("libc.o", "objconv -fcoff32 %f %o " .. tup.getconfig("KPACK_CMD"), "%B.obj")
 
-CRT0_ASM_SRC = AddPrefix("crt/", {
+tup.rule(FASM_SRC, "fasm %f %o", "%B.o")
-    "crt0.asm",
-})
-
-tup.rule(CRT0_ASM_SRC, "fasm %f %o", "%B.o")

programs/develop/ktcc/trunk/libc.obj/source/stdlib/_exit.c

@@ -6,7 +6,7 @@ void _exit(int status)
 {
     // return error and this is not abort
     if (status && status != 128) {
-        printf("exit code: %d\n", status);
+        fprintf(stderr, "exit code: %d\n", status);
     }
 
     if (__con_is_load) {

programs/develop/ktcc/trunk/libc.obj/source/stdlib/_mem.h

@@ -14,6 +14,8 @@ struct mem_node {
 
 struct mem_block {
     size_t size; // Size of the allocated memory block.
+
+    size_t a;   // align to 8bytes
 };
 
 // Macro to get a pointer to the user data area from a mem_node pointer.
@@ -32,13 +34,39 @@ struct mem_block {
 
 // Macro to check if two adjacent memory nodes are in the same block.
 // Checks if the end of the left node's allocated space is the start of the right node.
-#define MEM_NODES_ARE_IN_ONE_BLOCK(left, right) (GET_MEM_NODE_PTR(left) + left->size == (char*)right)
+#define MEM_NODES_ARE_IN_ONE_BLOCK(left, right) (GET_MEM_NODE_PTR(left) + ((struct mem_node*)left)->size == (char*)right)
 
-// Size of the blocks allocated at a time.
+// Size of the blocks allocated by `_ksys_alloc`
 #define ALLOC_BLOCK_SIZE 4096
 
+// Macro to merge two adjacent memory nodes.
+#define CHECK_SIDE_IN_OTHER_BLOCK(node, side) (side == NULL || ((side != NULL) && !MEM_NODES_ARE_IN_ONE_BLOCK(node, side)))
+
+inline struct mem_node* __mem_MERGE_MEM_NODES(struct mem_node* base, struct mem_node* addition)
+{
+    // addition is free && nodes base and addition both in one block, else merge is impossible
+    if (MEM_NODE_IS_FREE(addition) && MEM_NODES_ARE_IN_ONE_BLOCK(base, addition)) {
+        // just change size
+        const size_t s = addition->size + sizeof(struct mem_node);
+        base->size += s;
+        base->free += s;
+
+        // and delete addition from list
+        if (addition->next != NULL) {
+            addition->next->last = base;
+            base->next = addition->next;
+        } else {
+            base->next = NULL;
+        }
+        return base;
+    }
+    return NULL;
+}
+
 // Static pointer to the first memory node in the linked list.
 // This acts as the head of the memory pool.
 static struct mem_node* __mem_node = NULL;
 
+static struct mem_node* __last_biggest_mem_node = NULL;
+
 #endif // _LIBC_STDLIB_MEM_

programs/develop/ktcc/trunk/libc.obj/source/stdlib/abort.c

@@ -6,7 +6,7 @@ void abort()
 {
     ksys_thread_t t;
     _ksys_thread_info(&t, -1);
-    printf("\nAbort in %d\n", t.pid);
+    fprintf(stderr, "\nAbort in %d\n", t.pid);
 
     _exit(128);
 }

programs/develop/ktcc/trunk/libc.obj/source/stdlib/free.c

@@ -3,27 +3,6 @@
 #include <sys/ksys.h>
 #include "_mem.h"
 
-// Macro to merge two adjacent memory nodes.
-#define CHECK_SIDE_IN_OTHER_BLOCK(node, side) (side == NULL || ((side != NULL) && !MEM_NODES_ARE_IN_ONE_BLOCK(node, side)))
-
-inline void __mem_MERGE_MEM_NODES(struct mem_node* base, struct mem_node* addition)
-{
-    if (MEM_NODE_IS_FREE(addition) && MEM_NODES_ARE_IN_ONE_BLOCK(base, addition)) {
-        // just change size
-        const size_t s = addition->size + sizeof(struct mem_node);
-        base->size += s;
-        base->free = base->size;
-
-        // and delete addition from list
-        if (addition->next != NULL) {
-            addition->next->last = base;
-            base->next = addition->next;
-        } else {
-            base->next = NULL;
-        }
-    }
-}
-
 void free(void* ptr)
 {
     // Handle NULL pointer.
@@ -36,18 +15,28 @@ void free(void* ptr)
     // Mark the memory node as free.
     node->free = node->size;
 
+    if (__last_biggest_mem_node == node) {
+        if (node->last) {
+            __last_biggest_mem_node = node->last; // anyway node will be merged with next
+                                                  // and last and last will have size = last + node + next(if its free too)
+        }
+    }
+
     // Merge with the next node if possible.
     if (node->next != NULL)
         __mem_MERGE_MEM_NODES(node, node->next);
 
     // Merge with the previous node if possible.
     if (node->last != NULL)
-        __mem_MERGE_MEM_NODES(node->last, node);
+        node = __mem_MERGE_MEM_NODES(node->last, node);
+
+    if (node) {
 
         // If the current node is not adjacent to either the next or previous node,
         // it might be a separate block that can be freed.
-    if ((node->next == NULL || ((node->next != NULL) && !MEM_NODES_ARE_IN_ONE_BLOCK(node, node->next)))
+        if (MEM_NODE_IS_FREE(node) // check it because node maybe was merged with last
-        && (node->last == NULL || ((node->last != NULL) && !MEM_NODES_ARE_IN_ONE_BLOCK(node->last, node)))) {
+            && (node->last == NULL || !MEM_NODES_ARE_IN_ONE_BLOCK(node, node->next))
+            && (node->last == NULL || !MEM_NODES_ARE_IN_ONE_BLOCK(node->last, node))) {
 
             // Get a pointer to the mem_block header from the mem_node header.
             struct mem_block* block = (struct mem_block*)(((char*)node) - sizeof(struct mem_block));
@@ -73,8 +62,36 @@ void free(void* ptr)
                     }
                 }
 
+                struct mem_node* a = node->next;
+                struct mem_node* b = node->last;
+
+                if (!a && !b) {
+                    __last_biggest_mem_node = NULL;
+                } else if (a && !b) {
+                    __last_biggest_mem_node = a;
+                } else if (!a && b) {
+                    __last_biggest_mem_node = b;
+                } else if (a && b) {
+                    __last_biggest_mem_node = (a->free > b->free) ? a : b;
+                }
+
+                if (__last_biggest_mem_node == node) {
+                    if (node->next && !(node->last)) {
+                        __last_biggest_mem_node = node->next;
+                    } else if (node->last && !(node->next)) {
+                        __last_biggest_mem_node = node->last;
+                    } else if (node->next && node->last) {
+                        if (node->last->free > node->next->free) {
+                            __last_biggest_mem_node = node->last;
+                        } else {
+                            __last_biggest_mem_node = node->next;
+                        }
+                    }
+                }
+
                 // Free the memory block using the ksys_free function.
                 _ksys_free(block);
             }
         }
     }
+}

programs/develop/ktcc/trunk/libc.obj/source/stdlib/malloc.c

@@ -2,49 +2,75 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <sys/ksys.h>
+#include <stdbool.h>
 #include "_mem.h"
 
 // Macro to align a value to a specified alignment.
 // Ensures that the allocated memory is aligned to a certain boundary (e.g., 16 bytes).
 #define __mem_align(value, align) ((value + align - 1) & ~(align - 1))
 
-void* malloc(size_t size)
+static struct mem_node* __new_mem_node_from_exist(struct mem_node* current_node, size_t size, bool* from_empty_node)
 {
-    // Handle zero-size allocation.
+    struct mem_node* new_node = NULL;
-    if (size == 0) {
-        return NULL;
-    }
-
-    // Align the size to 16 bytes.
-    size = __mem_align(size, 16);
-
-    struct mem_node* current_node = __mem_node; // Start at the head of the linked list.
-    struct mem_node* new_node = NULL;           // Pointer to the new node that will be created.
-
-    // Iterate through the linked list of memory nodes.
-    while (current_node != NULL) {
     // Check if the current node has enough free space for the requested size.
     if (size + sizeof(struct mem_node) <= current_node->free) {
 
+        *from_empty_node = MEM_NODE_IS_FREE(current_node);
+        if (*from_empty_node) {
+            new_node = current_node;
+        } else {
             // Calculate the used memory in current node
             const size_t s = GET_MEM_NODE_USED_MEM(current_node);
 
             // Create a new memory node after the current node's used space.
             new_node = (struct mem_node*)(GET_MEM_NODE_PTR(current_node) + s);
 
-            // Set the size of the new node.
-            new_node->size = current_node->free - sizeof(struct mem_node);
-
             // Update current node's size
             current_node->size = s;
 
+            // Set the size of the new node.
+            // for new node give all free space in current node
+            new_node->size = current_node->free - sizeof(struct mem_node);
+
             // Mark current node as used.
             current_node->free = 0;
-
-            break; // Found a suitable node, exit the loop.
         }
+    }
+    return new_node;
+}
+
+void* malloc(size_t size)
+{
+    char b[32];
+
+    // Handle zero-size allocation.
+    if (size == 0) {
+        return NULL;
+    }
+
+    // Align the size to 8 bytes.
+    size = __mem_align(size, 8);
+
+    struct mem_node* current_node = NULL;
+    struct mem_node* new_node = NULL; // Pointer to the new node that will be created.
+    bool from_empty_node = false;
+
+    if (__last_biggest_mem_node != NULL)
+        new_node = __new_mem_node_from_exist(__last_biggest_mem_node, size, &from_empty_node); // try find free space in last created node
+
+    // if cant find in __last_biggest_mem_node
+    if (new_node == NULL) {
+        current_node = __mem_node; // Start at the head of the linked list.
+
+        // Iterate through the linked list of memory nodes.
+        while (current_node != NULL) {
+            new_node = __new_mem_node_from_exist(current_node, size, &from_empty_node);
+            if (new_node)
+                break; // Found a suitable node, exit the loop.
+
             current_node = current_node->next; // Move to the next node in the list.
         }
+    }
 
     // If no suitable node was found in the existing list:
     if (new_node == NULL) {
@@ -60,6 +86,8 @@ void* malloc(size_t size)
             return NULL;      // Return NULL to indicate allocation failure.
         }
 
+        block->size = s;
+
         // Create a new memory node after the mem_block header.
         new_node = (struct mem_node*)(block + sizeof(struct mem_block));
 
@@ -70,6 +98,7 @@ void* malloc(size_t size)
     // Set the free space in the new node.
     new_node->free = new_node->size - size;
 
+    if (!from_empty_node) {
         // Set the last pointer of the new node to the current node.
         new_node->last = current_node;
 
@@ -87,12 +116,17 @@ void* malloc(size_t size)
             // If the current node is NULL, the new node is the first node in the list.
             new_node->next = NULL;
         }
+    }
 
     // If the linked list was empty, set the head to the new node.
     if (__mem_node == NULL) {
         __mem_node = new_node;
     }
 
+    if (__last_biggest_mem_node == NULL || new_node->free > __last_biggest_mem_node->free) {
+        __last_biggest_mem_node = new_node;
+    }
+
     // Return a pointer to the user data area of the new node.
     return GET_MEM_NODE_PTR(new_node);
 }

programs/develop/ktcc/trunk/libc.obj/source/stdlib/realloc.c

@@ -3,33 +3,60 @@
 #include <sys/ksys.h>
 #include "_mem.h"
 
-void* realloc(void* ptr, size_t newsize)
+// realloc mem. using if other ways not working
+void* fail_realloc(void* ptr, size_t newsize)
 {
-    // Handle NULL pointer.
-    if (ptr == NULL)
-        return NULL;
-
-    // Get a pointer to the mem_node header from the user data pointer.
-    struct mem_node* node = GET_MEM_NODE_HEADER(ptr);
-    void* new_ptr;
-
-    // If the new size is smaller than or equal to the current size:
-    if (node->size >= newsize) {
-        // Update the free space in the current node.
-        node->free = node->size - newsize;
-        // Return the original pointer.
-        new_ptr = ptr;
-    } else {
     // Allocate a new block of memory with the new size.
-        new_ptr = malloc(newsize);
+    void* new_ptr = malloc(newsize);
 
     // If both the old pointer and the new pointer are not NULL:
     if (ptr != NULL && new_ptr != NULL) {
         // Copy the data from the old block to the new block.
-            memcpy(new_ptr, ptr, min(newsize, node->size));
+        memcpy(new_ptr, ptr, min(newsize, GET_MEM_NODE_USED_MEM(GET_MEM_NODE_HEADER(ptr))));
-            // Free the old block.
-            free(ptr);
     }
+
+    if (ptr) {
+        free(ptr);  // Free the old block.
+    }
+
+    return new_ptr;
+}
+
+void* realloc(void* ptr, size_t newsize)
+{
+
+    void* new_ptr = NULL;
+    struct mem_node* node = NULL;
+
+    if (ptr && newsize) {
+
+        // Get a pointer to the mem_node header from the user data pointer.
+        node = GET_MEM_NODE_HEADER(ptr);
+
+        if (node->size >= newsize) { // current node have enough mem
+                                     // it work always if newsize is smaller
+            // Update the free space in the current node.
+            node->free = node->size - newsize;
+            // Return the original pointer.
+            new_ptr = ptr;
+        } else if (node->next && MEM_NODE_IS_FREE(node->next) && node->size + node->next->size >= newsize) {
+            // So what happens here is that the node merges with the next node if their volume is sufficient.
+            // And a reallock is called in the hopes that the first condition will be met.
+            // if merge failed realloc anyway return pointer, but it will got from `fail_realloc`
+            // it faster than merge with last node, because its not make a copy/move
+            new_ptr = realloc(GET_MEM_NODE_PTR(__mem_MERGE_MEM_NODES(node, node->next)), newsize);
+        } else if (node->last && MEM_NODE_IS_FREE(node->last) && node->size + node->last->size >= newsize) {
+            struct mem_node* l = node->last;
+
+            l = __mem_MERGE_MEM_NODES(l, node);
+            if (l)
+                memmove(GET_MEM_NODE_PTR(l), ptr, GET_MEM_NODE_USED_MEM(node));
+            new_ptr = realloc(GET_MEM_NODE_PTR(l), newsize);
+        } else {
+            new_ptr = fail_realloc(ptr, newsize);
+        }
+    } else {
+        new_ptr = fail_realloc(ptr, newsize);
     }
 
     // Return the new pointer.