From b34189b028529bf0f0b97b69f8d9184424a61583 Mon Sep 17 00:00:00 2001 From: Greg Bowne Date: Sat, 17 Feb 2024 16:29:08 -0800 Subject: [PATCH] fixed math issue and some minor issues renamed custom free function --- main.c | 162 +++++++++++++++++++++++++++++---------------------------- 1 file changed, 83 insertions(+), 79 deletions(-) diff --git a/main.c b/main.c index b9c6584..a87cfc2 100644 --- a/main.c +++ b/main.c @@ -31,10 +31,16 @@ struct block *extend_heap(size_t s) struct block *b = (struct block *)sbrk(0); // Get the current break - if (sbrk(BLOCK_SIZE + s) == (void *)-1) // Extend the break by s bytes + // Attempt to extend the break by s bytes + void *new_break = sbrk(BLOCK_SIZE + s); + if (new_break == (void *)-1) + { + // Handle the error, e.g., by setting an error code or printing an error message + fprintf(stderr, "Failed to extend heap by %zu bytes.\n", s); return NULL; + } - b->size = s; // Corrected from b->size to b->size + b->size = s; b->prev = last; b->next = NULL; b->free = 0; @@ -80,13 +86,13 @@ struct block *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 = remainderSize; + newBlock->size = remainderSize; // Subtract the size of the block header 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->size = newBlockSize; // Subtract the size of the block header in->next = newBlock; // Insert the new block into the linked list of blocks @@ -105,17 +111,15 @@ struct block *find_best_fit(size_t s) while (current) { if (current->free && current->size >= s) - { - if (best_fit && current->size < best_fit->size) // Check for NULL before comparison { + if (best_fit == NULL || current->size < best_fit->size) { best_fit = current; } } current = current->next; } - return best_fit; - } + return best_fit; // This return statement is now outside the while loop } /// Will find or allocate a memory block. @@ -197,96 +201,96 @@ void *realloc(void *ptr, size_t new_size) /// 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) +void free(void *ptr) { - if (!ptr) - { - return; - } + 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 - } + 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; + 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; - } + // 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; - } - } + // 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; // Update the prev pointer of the next block + } + } - // After merging, update the 'last' pointer if necessary - if (!b->next) - { - last = 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)); - } + // 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; + size_t total_size = 0; + struct block *current = first; - while (current != NULL) - { - total_size += current->size; - current = current->next; - } + while (current != NULL) + { + total_size += current->size; + current = current->next; + } - return total_size; + 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 + 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; + *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 + 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 + free(a); // Free memory for a + free(b); // Free memory for b + free(c); // Free memory for c - return 0; + return 0; } \ No newline at end of file