Re: [Valgrind-developers] valgrind: r6640 - trunk/memcheck

[Julian S. <js...@ac...>]

Dirk

> the patch is below, and its not working. probably I'm doing something
> stupid,

No - this is subtle.

> but I can't find an example for a wrapper function anywhere. 

auxprogs/libmpiwrap.c has a huge collection of them.

You've hit the distinction between replacement functions and wrapper
functions.  A replacement (eg malloc) simply replaces some function;
there is no way to call onwards to the original.  A wrapper function
is more powerful - it gives you a way to find out the original
and call onwards to it.

I think your wrapper might produce an infinite loop, since the call to
putenv just goes back to the wrapper.  Try the code below.

All this strange stuff is documented at
http://www.valgrind.org/docs/manual/manual-core.html#manual-core.wrapping

J

/* putenv */
int VG_WRAP_FUNCTION_ZU(m_libc_soname, putenv) (char* string);
int VG_WRAP_FUNCTION_ZU(m_libc_soname, putenv) (char* string)
{
    OrigFn fn;
    char* p;
    VALGRIND_GET_ORIG_FN(fn);  // remember the original

    p = string;
    if (string)
    {
        int len = 0;
        while (*p++)
            len++;

        VALGRIND_CHECK_MEM_IS_DEFINED(string, len+1);
    }

    // call original, ultra-magic hacks to avoid recursion
    unsigned long tmp;
    CALL_FN_W_W(tmp, fn, (unsigned long)string);
    return (int)tmp;
}