Why Do I Get the Error malloc Invalid Size Unsorted

Why Do I Get the Error malloc Invalid Size Unsorted

Have you ever encountered the error message “malloc(): invalid size (unsorted)” in your C or C++ program and wondered why it occurs? This issue can be quite perplexing, but fear not! Let’s delve into the common reasons behind this error and explore some insightful solutions to help you overcome it.

Understanding the root cause of this error is key to efficiently troubleshooting and rectifying it.

Common Causes of malloc() Invalid Size Error

The error message “malloc(): invalid size (unsorted)” typically occurs in C or C++ programs when there’s an issue with memory allocation. Let’s break down the possible reasons for this error:

  1. Incorrect Memory Allocation Size:

    • The error message suggests that the size provided to malloc or realloc is invalid.
    • Double-check the size you’re passing to these functions. Ensure it’s a positive value and correctly represents the amount of memory you need.
    • In your specific case, the error occurs within the updateCells function. Let’s examine it further.
  2. Memory Corruption or Buffer Overflow:

    • Memory corruption can lead to unexpected behavior, including invalid chunk sizes.
    • Check your code for any buffer overflows, out-of-bounds array accesses, or invalid pointer operations.
    • Make sure you’re not writing beyond allocated memory bounds.
  3. Example Code Analysis:

    • You’ve shared a minimal example that works without SDL2. Let’s focus on that.
    • In your updateCells function, you reallocate memory for the cells array based on the new grid dimensions.
    • Here’s the relevant snippet from your example:
      cells = (cellState_t *)realloc(cells, (gridRow * gridCol) * sizeof(cellState_t));
    • Ensure that gridRow and gridCol are valid positive values. If they are zero or negative, it could cause the error.
    • Also, verify that the previous memory allocation (cells = calloc(...)) was successful.
  4. Debugging Steps:

    • To diagnose further, consider the following steps:
      • Print the values of gridRow and gridCol before the realloc call.
      • Check if the previous memory allocation (calloc) succeeded.
      • Inspect other parts of your code that interact with the cells array.

Dynamic Memory Allocation

Dynamic memory allocation is a fundamental concept in programming, especially in languages like C. Let’s delve into it:

  1. What is Dynamic Memory Allocation?

    • Dynamic memory allocation refers to the process of assigning memory space during runtime (when the program is executing) rather than at compile time.
    • Unlike static memory allocation (where memory is allocated at compile time), dynamic allocation allows for greater flexibility when dealing with varying amounts of data.
  2. Why Use Dynamic Memory Allocation?

    • Unknown Memory Requirements: In many cases, we don’t know the exact amount of memory needed beforehand.
    • Efficiency: Dynamic allocation helps avoid wasting memory by allocating only what’s necessary.
    • Data Structures: It’s essential for creating dynamic data structures like linked lists, trees, and graphs.
  3. Functions for Dynamic Memory Allocation in C:

    • malloc(): Stands for memory allocation. It reserves a block of memory of the specified number of bytes and returns a pointer to the first byte. The memory is uninitialized.
      • Syntax: ptr = (castType*) malloc(size);
      • Example: ptr = (float*) malloc(100 * sizeof(float)); (Allocates 400 bytes for floats).
    • calloc(): Stands for contiguous allocation. It allocates memory and initializes all bits to zero.
      • Syntax: ptr = (castType*) calloc(n, size);
      • Example: ptr = (float*) calloc(25, sizeof(float)); (Allocates contiguous space for 25 floats).
    • realloc(): Used to resize dynamically allocated memory.
    • free(): Explicitly releases dynamically allocated memory. Memory created with malloc() or calloc() doesn’t get freed automatically.
  4. Example Programs:

    • Using malloc() and free():
      int main() {
          int n, i, *ptr, sum = 0;
          printf("Enter number of elements: ");
          scanf("%d", &n);
          ptr = (int*) malloc(n * sizeof(int));
          if (ptr == NULL) {
              printf("Error! Memory not allocated.");
          printf("Enter elements: ");
          for (i = 0; i < n; ++i) {
              scanf("%d", ptr + i);
              sum += *(ptr + i);
          printf("Sum = %d", sum);
          return 0;
    • Using calloc() and free():
      int main() {
          int n, i, *ptr, sum = 0;
          printf("Enter number of elements: ");
          scanf("%d", &n);
          ptr = (int*) calloc(n, sizeof(int));
          if (ptr == NULL) {
              printf("Error! Memory not allocated.");
          printf("Enter elements: ");
          for (i = 0; i < n; ++i) {
              scanf("%d", ptr + i);
              sum += *(ptr + i);
          printf("Sum = %d", sum);
          return 0;
    • In both examples, we dynamically allocate memory for an array of integers and calculate their sum.

Common Causes of ‘malloc invalid size’ Error

The “malloc invalid size” error often occurs in C or C++ programs during dynamic memory allocation. Let’s explore some common reasons for this error:

  1. Incorrect Allocation Size:

    • When using malloc, ensure that you allocate the correct amount of memory. For example, if you allocate space for a pointer (e.g., malloc(sizeof(char*))), you should not overwrite it with strings. Allocate memory for the actual characters you intend to store.
    • In your specific example, the issue lies in allocating memory for a single pointer (char*) instead of the actual string. You don’t need to allocate space for the pointer itself; it’s a local variable. Allocate memory for the concatenated string instead.
  2. Double-Free:

    • Attempting to free the same memory block multiple times (a “double-free”) can lead to memory corruption. Ensure that you only free memory once.
  3. Writing Beyond Allocated Memory:

    • Writing past the end of an allocated memory block can corrupt adjacent memory. Be cautious when manipulating strings or arrays to avoid buffer overflows.
  4. Uninitialized or Freed Memory Access:

    • Accessing memory that has not been initialized or has already been freed can cause corruption. Always initialize memory before using it and avoid accessing freed memory.
  5. Memory Leaks:

    • Not freeing allocated memory properly can lead to memory leaks. Always release memory using free when it’s no longer needed.

Remember to run your code through tools like Valgrind

For more details, you can refer to the Stack Overflow discussion on this topic.

Common Memory Allocation Errors and Solutions

The “malloc(): invalid size (unsorted)” error can be quite perplexing, but let’s break it down. This error typically occurs when there’s a memory allocation issue in your code. Let’s explore some common reasons and potential solutions:

  1. Memory Corruption:

    • The error message suggests that there might be memory corruption somewhere in your program.
    • Run your code through a memory analysis tool like Valgrind to identify memory-related issues.
    • Valgrind can pinpoint memory leaks, invalid reads/writes, and other memory problems.
  2. Insufficient Memory Allocation:

    • Check the line where you allocate memory using malloc.
    • Ensure that you allocate enough memory for your data structures.
    • For example, if you’re allocating memory for a string, consider the length of the string plus one for the null terminator.
  3. String Manipulation Issues:

    • In your specific case, you mentioned the line: sql_current->next = (SqlNode *)malloc(sizeof(SqlNode));.
    • Verify that sizeof(SqlNode) correctly reflects the size of your SqlNode structure.
    • Also, ensure that any string manipulation (e.g., concatenation) doesn’t exceed allocated memory bounds.
  4. Unexpected Chunk Size:

    • The “invalid size” mentioned in the error message refers to an internal “chunk size” used by the memory manager.
    • This value is not your explicit malloc size argument but an internal bookkeeping value.
    • Since it’s invalid, there’s likely a memory corruption issue elsewhere in your code.
  5. Memory Leaks and Double Frees:

    • Check if you’re inadvertently freeing memory twice (double free) or leaking memory (not freeing it at all).
    • Make sure you’re managing memory correctly throughout your program.
  6. Googling the Error:

    • You mentioned that Googling the error suggests the problem could be unrelated to the specific line.
    • Unfortunately, that’s true. Memory issues can have far-reaching consequences.
    • Consider reviewing other parts of your code for potential memory-related issues.

Common Memory Allocation Errors and Prevention Techniques

The “malloc(): invalid size (unsorted)” error typically occurs when using memory allocation functions like malloc, realloc, or calloc. Let’s delve into some common reasons for encountering this issue and how to prevent it:

  1. Incorrect Memory Allocation Size:

    • Ensure that you allocate the correct amount of memory. If you request an invalid size (e.g., negative or zero), the memory manager will raise this error.
    • Double-check the size calculation in your realloc or calloc calls. Make sure you multiply by the correct size of the data type you’re allocating (e.g., sizeof(int)).
  2. Memory Corruption:

    • The error message might indicate memory corruption. If your program writes beyond allocated memory bounds, it can corrupt the internal data structures used by the memory manager.
    • Use tools like Valgrind to detect memory issues and pinpoint the problematic code.
  3. Uninitialized Pointers or Double-Free:

    • Ensure that pointers are properly initialized before using them with memory allocation functions.
    • Avoid double-free scenarios where you free the same memory block more than once.
  4. Fragmentation and Heap Management:

    • Fragmentation can lead to unsorted chunks, causing the error. Fragmentation occurs when memory is allocated and freed in a non-contiguous manner.
    • Consider using memory pools or custom memory management techniques to reduce fragmentation.
  5. Debugging Techniques:

    • Use debugging tools (e.g., gdb, Valgrind) to identify the exact location of the error.
    • Check your code for any out-of-bounds array accesses or buffer overflows.

Here’s an example of how to handle memory allocation and resizing in C:


typedef enum cellState { dead, live, potentialDead, potentialLive } cellState_t;
size_t gridRow, gridCol, gridSizeW, gridSizeH;
cellState_t *cells;

bool initCells(void) {
    cells = calloc(gridRow * gridCol, sizeof(cellState_t));
    if (cells == NULL) {
        return false;
    return true;

bool updateCells(int w, int h) {
    size_t x, y, oldGridCol, oldGridRow;
    oldGridCol = gridCol;
    oldGridRow = gridRow;
    gridRow = w / gridSizeW;
    gridCol = h / gridSizeH;

    // Reallocate memory for cells
    cells = (cellState_t *)realloc(cells, gridRow * gridCol * sizeof(cellState_t));
    if (cells == NULL) {
        return false;

    // Copy existing data to the new grid
    for (y = 0; y < oldGridRow; y++) {
        for (x = 0; x < oldGridCol; x++) {
            writeCell(y, x, *(cells + (x + (y * oldGridCol))));
    return true;

int main() {
    // Initialize grid size and cells
    gridSizeW = 25;
    gridSizeH = 25;
    gridRow = 640 / gridSizeW;
    gridCol = 480 / gridSizeH;

    if (!initCells()) {
        printf("Failed to initialize cells!\\n");
        return EXIT_FAILURE;

    // Example usage: updateCells(640, 480);
    // ...

    // Clean up memory when done
    return EXIT_SUCCESS;

Remember to handle memory allocation errors gracefully and always free allocated memory when it’s no longer needed. Debugging tools and thorough testing are essential for preventing memory-related errors in your programs.

In conclusion, the error message ‘malloc invalid size unsorted’ often stems from various memory allocation issues in C or C++ programming. By ensuring correct memory allocation size, preventing memory corruption, avoiding double-frees, and understanding dynamic memory management, you can mitigate the occurrence of this error. Remember, handling memory allocation carefully, using debugging tools like Valgrind, and practicing good coding habits are crucial to resolving the ‘malloc(): invalid size (unsorted)’ error effectively.

By following the guidelines outlined in the article, you can navigate through memory-related challenges with confidence and precision.


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