CODEWITHSUNDEEP
clinuxcrashfopenfclose
user5454875
user5454875

Reputation:

Crash on calling free()

I don't understand why the following piece of code make my programm crash. 'fp' isn't modified after doing 'fopen()'.

    FILE * fp;
    char * line = NULL;
    int len = 0;
    int read;
    char filePath[100] = "";

    //Quick concatenate, I should use concatain but nah.
    snprintf(filePath,sizeof(filePath), "%s/%s/%s",FOLDER_MAIN, "test", "data.txt");
    fp = fopen(filePath, "r");
    if (fp != NULL)
    {
        while ((read = getline(&line, &len, fp)) != -1)
        {
            if(startsWith(line, "value:"))
            {
                removeSubstring(line, "value:");
                removeSubstring(line, " ");
                removeSubstring(line, "\t");
                removeSubstring(line, "\n");
                printf("%d\t%s\n", 0, line);
            }
        }
        fclose(fp);

        //Free line pointer, is it really needed ?
        if (line)
           free(line);
    }

int StartsWith(const char *a, const char *b)
{
   if(strncmp(a, b, strlen(b)) == 0)
       return 1;

   return 0;
}

void removeSubstring(char *s,const char *toremove)
{
    while( s=strstr(s,toremove))
        memmove(s,s+strlen(toremove),1+strlen(s+strlen(toremove)));
}

EDIT: Also, 'free(line)' make also the programm crash. I added removeSubstring and StartsWith function, I hope it helps. Anyway, I don't think it impact much on the programm, since the problem is with fp...

Upvotes: 1

Views: 105

Answers (1)

Stargateur
Stargateur

Reputation: 26757

Your code is undefined behavior.

The prototype of getline is clear ssize_t getline(char **lineptr, size_t *n, FILE *stream);, you must use correct type specially when you use pointer !

size_t len = 0;
ssize_t read;

The compiler should have warning you.

Upvotes: 3

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