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Tuesday September 20, 2005

Stupid errors I have made, #1 of several thousand

Today's stupid programming error involves recursive directory handing in C. I was doing this, and wondering why it didn't work:

void
foo(char *path)
{
        /* stuff */
        if(condition) {
               foo(dirname(path));
               /* other stuff */
        }
        /* yet more stuff */
}

Can you see the problem? Yup, that's right, dirname() modifies the string pointed at by its argument, so when you pop up a level, your path is still trimmed. The solution is to strdup(path) before the recursive call, and free() the copy afterwards.

D'oh!

Tag: Bugs