Visual C ++的奇怪错误

Question

Alright, this is my code so far

int main()
{
    char buffer[10];
    int arraySize = -1;
    FILE *fp;
    int i;  
    char filename[10];
    int userNo = 1;
    char stockArray[18][15];
    sprintf(filename, "file%d", userNo);
    fp = fopen(filename, "r");
    while(fgets(buffer, 30, fp) != NULL)
    { 
        if(buffer[0] == '<' && buffer[1] == 's')
        {
            arraySize++;
        }
        else if(buffer[0] == '<' && buffer[1] == '/'){printf("< char\n");}
        else
        {
            int t = 0;
            int r = 0;
            while(buffer[t] != '>')
            {
                t++;
            }
            t++;
            char holder[15] = {'\0'};
            while(buffer[t] != '<')
            {
                holder[r] = buffer[t];
                t++;
                r++;
            }
            strncpy(stockArray[arraySize], holder, r);
            printf("%s\n", stockArray[arraySize]);
        }
    }
    fclose(fp);
}

I'm running into two strange issues. First, when I do the printf statement, it prints the proper data just fine, then does the following: if the first word is "banana" and the next is "123" it prints "123ana" and then a bunch of weird character that ends with, I kid you not, a smiley face.

Then, after the program is done and finished, I get a "Run-Time Check Failure #2 - Stack around the variable 'filename' was corrupted." error.

I'm using VS2010 and C++, and all my experience thus far has been with GCC and C, where I've never encountered these problems before. Any advice would be appreciated

Answer 1

Your input buffer is 10 chars long

char buffer[10];

But then you tell fgets to read up to 30 characters into the buffer

fgets(buffer, 30, fp)

That is likely to have "funny" effects!

Answer 2

One thing I recognized on visual inspection is that your holder is not properly null-terminated. You might add a line

holder[r++] = '\0';

after your while-loop.

Answer 3

Its very difficult to point out the problem, without understanding what exactly you're doing, and what the file contains.

But I still suggest one thing and try:

strncpy(stockArray[arraySize], holder, r);
stockArray[arraySize][r] = '\0'; //do this before printf!

In general, make sure all your c-strings are null-terminated. Or else you will face the usual problem arises due to lack of null character.