Anti_Virus.exe has triggered a breakpoint. C language

Question

I wrote an "Anti Virus" (not a real one - just to learn) which uses the heap and sometimes when it needs to use the heap it's break with the message on the topic then it gives me the message: "Debug Assertion Failed" and: "expression: _crtisvalidheappointer(puserdata)" and i realy don't know why... In the code it's happen in the function run when the while loop is on his 5th iteration in this line:

if (!(results = (char**)realloc(results, sizeof(results) + sizeof(char*))))

The function:

void run(char* dir_path, char* virus_path, char mode)
{
    DIR* dir = NULL;
    FILE* virus = NULL;
    struct dirent* cur_file;  // cur_file is a pointer for struct dirent which represnts the file we are checking now (current file)
    char** results = NULL;  // resullts will be an array of strings to write in the log
    int results_len = 0, i = 0;
    char* file_path = NULL;

    //checks the arguments:
    if (!(dir = opendir(dir_path)))  // argv[1] should be the directory
    {
        printf("The path that given as the first argument doesn't point to a directory / ");
        printf("an error has occurred while opening the directory\n");
        return -1;
    }
    if (!(virus = fopen(virus_path, "rb")))
    {
        printf("The path that given as the second argument doesn't point to a file / ");
        printf("an error has occurred while opening the file\n");
        closedir(dir);
        return -1;
    }

    //running on the file in the directory:
    while (cur_file = readdir(dir))  // at the end of the directory readdir() will return NULL
    {
        if (!(strcmp(cur_file->d_name, ".")))  // at the first time wer'e reading from a directory the value of d_name will be "."
        {
            continue;
        }
        if (!(strcmp(cur_file->d_name, ".."))) //at the second time wer'e reading from a directory the value of d_name will be ".."
        {
            continue;
        }

        if (!(file_path = (char*)malloc(strlen(dir_path) + cur_file->d_namlen + 2))) //1 for \ between dir_path and d_name and 1 for the NULL
        {
            closedir(dir);
            fclose(virus);
            return -1;
        }
        strcpy(file_path, dir_path);
        strcat(file_path, "\\");
        strcat(file_path, cur_file->d_name);
        if (!(results)) // if results == NULL -> if didn't allocated memory for results already
        {
            if (!(results = (char**)malloc(sizeof(char*))))
            {
                printf("Problem with malloc\n");
                free(file_path);
                closedir(dir);
                fclose(virus);
                return -1;
            }
        }
        else
        {
            if (!(results = (char**)realloc(results, sizeof(results) + sizeof(char*))))
            {
                printf("Problem with realloc\n");
                for (i = 0; i < results_len; i++)
                {
                    free(results[i]);
                }
                free(file_path);
                free(results);
                closedir(dir);
                fclose(virus);
                return -1;
            }
        }    
        results[results_len] = check_file(file_path, virus, mode);
        if(results[results_len] == -1) // results_len will be updated later (just malloced)
        {
            for (i = 0; i < results_len; i++)
            {
                free(results[i]);
            }
            free(file_path);
            free(results);
            closedir(dir);
            fclose(virus);
            return -1;
        }
        results_len++;
        free(file_path);
    }
    fclose(virus);
    closedir(dir);
    write_to_log(dir_path, virus_path, mode, results, results_len);
}

and the function check_file returns a char* (string) which malloced in check_file and will be free in other function.

Does someone knows the reason? Thank You

sizeof does not do what you think it does (it does not tell you the size in memory of a string). You probably want strlen. — Max, May 31 '16 at 21:09
Oh I'm so stupid, Thank you! you very helped me and now the program is better and doing almost all but there is a little bug already (triggered a breakpoint) and now its on the realloc line: if (!(results = (char**)realloc(results, sizeof(results) + sizeof(char*)))) — saar, May 31 '16 at 22:40
you really need to improve your error handling instead of having all that code duplication - makes the code hard to follow — M.M, Jun 01 '16 at 01:07
[Don't cast the result of `malloc` in C](http://stackoverflow.com/q/605845/995714) — phuclv, Jun 01 '16 at 14:19
Why not? And I don't think that that's my problem (because it works in other codes) — saar, Jun 01 '16 at 17:21

score 1 · Accepted Answer · answered Jun 02 '16 at 01:11

This line:

        if (!(results = (char**)realloc(results, sizeof(results) + sizeof(char*))))

Is not increasing the size of results (and therefore you are stomping over the end of it as result_len increases). You probably want to use (result_len + 1)*sizeof(char*), since you are already storing the number of strings in results.

Anti_Virus.exe has triggered a breakpoint. C language

1 Answers1