Substitute or workaround for asprintf on AIX

I'm trying to build python-kerberos on AIX. kerberospw.c uses a call to asprintf, but from what Google is telling me, asprintf does not exist on AIX.

I saw http://www.koders.com/c/fidAA9B130D588302673A28B568430A83131B7734C0.aspx?s=windows.h, which looks like I could create a stand-in asprintf, but I don't know where this would go or how I would #include it in kerberospw.c.

Is there a way I can use the koders.com example or some other code to "fake" asprintf? Can I just include the asprintf function as shown in kerberospw.c? I am not a C coder, but

asprintf (char **resultp, const char *format, ...)

doesn't look like a valid signature to me with the dots at the end. The relevant line from kerberospw.c is below

asprintf(&message, "%.*s: %.*s", (int) result_code_string.length,
(char *) result_code_string.data,
(int) result_string.length,
(char *) result_string.data);

I realize I could contact the author of python-kerberos, but a) I think it would be helpful to have a potential patch if I did so, and b) there might be other software I run across that uses asprintf, and it would be nice to have a workaround.

The asprintf is a variation of the printf family of function that allocate a buffer to hold the memory for the formatted string and return it. It is a function with a variable number of argument (hence the ... in the declaration that is valid C code). You can find a description here.

It can be reimplemented relatively easily if the vsnprintf is functioning correctly (ie, return an error if the buffer is too small to hold the formatted string).

Here is such an implementation:

#include <stdarg.h>

int asprintf(char **ret, const char *format, ...)
{
    va_list ap;

    *ret = NULL;  /* Ensure value can be passed to free() */

    va_start(ap, format);
    int count = vsnprintf(NULL, 0, format, ap);
    va_end(ap);

    if (count >= 0)
    {
        char* buffer = malloc(count + 1);
        if (buffer == NULL)
            return -1;

        va_start(ap, format);
        count = vsnprintf(buffer, count + 1, format, ap);
        va_end(ap);

        if (count < 0)
        {
            free(buffer);
            return count;
        }
        *ret = buffer;
    }

    return count;
}