Return to Answer

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const char*, which might be free'd.

**** Error in `/root/CLionProjects/BitmapTest/cmake-build-debug/BitmapTest':
munmap_chunk(): invalid pointer: 0x0000000000401d7b ***
======= Backtrace: =========
[...]

You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        // return "Not enough memory for error message";
        const char* error_message = "Not enough memory for error message";
        size_t len = strlen(error_message);
        char* error = (char*) malloc(len*sizeof(char) + 1);
        strcpy(error, error_message);
        return error;
    }

    strcpy(copy, string);
    return copy;
}

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const char*, which might be free'd.

**** Error in `/root/CLionProjects/BitmapTest/cmake-build-debug/BitmapTest':
munmap_chunk(): invalid pointer: 0x0000000000401d7b ***
======= Backtrace: =========
[...]

You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        // return "Not enough memory for error message";
        const char* error_message = "Not enough memory for error message";
        size_t len = strlen(error_message);
        char* error = (char*) malloc(len*sizeof(char) + 1);
        if(error == NULL)
           { /* TODO: return null or exit the program */ }
        strcpy(error, error_message);
        return error;
    }

    strcpy(copy, string);
    return copy;
}

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const char*, which might be free'd. You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        // return "Not enough memory for error message";
        const char* error_message = "Not enough memory for error message";
        size_t len = strlen(error_message);
        char* error = (char*) malloc(len*sizeof(char) + 1);
        strcpy(error, error_message);
        return error;
    }

    strcpy(copy, string);
    return copy;
}

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const char*, which might be free'd.

**** Error in `/root/CLionProjects/BitmapTest/cmake-build-debug/BitmapTest':
munmap_chunk(): invalid pointer: 0x0000000000401d7b ***
======= Backtrace: =========
[...]

You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        // return "Not enough memory for error message";
        const char* error_message = "Not enough memory for error message";
        size_t len = strlen(error_message);
        char* error = (char*) malloc(len*sizeof(char) + 1);
        strcpy(error, error_message);
        return error;
    }

    strcpy(copy, string);
    return copy;
}

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const string, which might be free'd. You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        return "Not enough memory for error message";
    }
    strcpy(copy, string);
 
    return copy;
}

And one more thing:
You define the return value as char*, then you proceed to return "copy" with malloc, but if it fails, you return a const char*, which might be free'd. You should malloc this string.

char *_string_duplicate(const char *string)
{
    char *copy = (char*) malloc(sizeof(*copy) * (strlen(string) + 1));
    if (copy == NULL)
    {
        // return "Not enough memory for error message";
        const char* error_message = "Not enough memory for error message";
        size_t len = strlen(error_message);
        char* error = (char*) malloc(len*sizeof(char) + 1);
        strcpy(error, error_message);
        return error;
    } 

    strcpy(copy, string);
    return copy;
}