setuid and sqlite can't open database

Question

I have a fairly simple c++ program that needs to manage a local "cache" in a secure way. My idea was to make the executable setuid-root and store the cache in root's home dir.

I enter setuid mode by calling seteuid(0). I then chroot to root's home dir then try to open the cache. The open fails with sqlite's error: unable to open database file.

    try {
        /*
         * open the SQLite DB.
         */

#ifdef DEBUG
    syslog(LOG_AUTHPRIV | LOG_INFO,
            "%s: am I root: uid=%d: euid=%d", __func__, getuid(), geteuid());
#endif

        std::string rootDir = My::My::getRootDir();

        if (chroot(rootDir.c_str()) != 0) {
            snprintf(error, 1024, "%s: Could not chroot for cache: %s",
                    __func__, strerror(errno));
            syslog(LOG_AUTHPRIV | LOG_INFO, "%s", error);
            throw My::MyException(error);
        }

        /*
         * Create a new cache DB without "other" privs
         */
        umask(0007);

        if ((sqlite3_open(My_Lib::LocalCache::DBCacheFileName.c_str(),
                &sqlite)) != SQLITE_OK) {
            if (sqlite == NULL) {
                snprintf(error, 1024,
                        "%s: Could not open cache, dbh is null", __func__);
            } else {
                snprintf(error, 1024,
                        "%s: Could not open cache, dbh error: %s", __func__, 
                        sqlite3_errmsg(sqlite));
            }
            syslog(LOG_AUTHPRIV | LOG_INFO, "%s", error);
            throw My::MyException(error);
        }

        ...

The DEBUG syslog statement that prints the real and effective uids shows a real uid suitable for a non-root user. The euid is zero. Root's home dir perms are 750.

What am I missing?