Question

I am trying to read from the while questions.txt which has the following format:

Question\n
Difficulty:Cost:Prize\n
Correct Answer\n
Answer 1\n
.
.
.
Answer i\n
\n

The following is a function that reads from questions.txt and stores it to a temporary node to be added to a linked list.

pQuestionType loadQuestions(pQuestionType pFirst)
{
    pQuestionType pTemp = malloc(sizeof(pQuestionType));
    FILE* pFile;
    string sFilename, sTemp;
    char cDump;
    int nTemp, n=0;
    gotoxy(0,0);
    system("cls");
    printf("Enter file name: ");
    gets(sFilename);
    pFile = fopen(sFilename, "rt");
    while(!feof(pFile))
    {
        printf("Iteration \n");
        fgets(sTemp, 255, pFile);
        strcpy(pTemp->sQuestion, sTemp);
        pTemp->sQuestion[strlen(sTemp)-1] = '\0';
        printf("Add question success\n");

        fscanf(pFile, "%d%c", &nTemp, &cDump);
        pTemp->nDifficulty = nTemp;
        printf("Add difficulty success\n");

        fscanf(pFile, "%d%c", &nTemp, &cDump);
        pTemp->nCost = nTemp;
        printf("Add cost success\n");

        fscanf(pFile, "%d%c", &nTemp, &cDump);
        pTemp->nWinnings = nTemp;
        printf("Add winnings success\n");

        fgets(sTemp, 255, pFile);
        strcpy(pTemp->sCorrect, sTemp);
        pTemp->sCorrect[strlen(sTemp)-1] = '\0';
        strcpy(pTemp->sAnswers[0], sTemp);
        pTemp->sAnswers[0][strlen(sTemp)-1] = '\0';
        printf("Add answer success\n");

        for(n=1; n<10; n++)
        {
            fgets(sTemp, 255, pFile);
            if(*sTemp == '\n')break;
            strcpy(pTemp->sAnswers[n], sTemp);
            pTemp->sAnswers[n][strlen(sTemp)-1] = '\0'; 
        }
        printf("Add choices success\n");

        printf("\n");   
        pFirst = addQuestion(pFirst, pTemp);        
        if(*sTemp == EOF) break;
    }
    fclose(pFile);

    return pFirst;
}

I crash at the third iteration when the program tries to read the difficulty of my third question. What causes this and what can I do to fix my code?

Answer 1

pQuestionType pTemp = malloc(sizeof(pQuestionType));

If pQuestionType is a pointer type (and it appears to be since neither pFirst nor pTemp have a * character anywhere near their declaration), then its size is going to be the size of a pointer (currently likely to be 4 or 8).

So this malloc will almost certainly not give you enough memory. You need to use sizeof(*pTemp) instead.