X-Authentication-Warning: delorie.com: mail set sender to djgpp-bounces using -f X-Received: by 10.224.163.14 with SMTP id y14mr67097260qax.3.1375130704150; Mon, 29 Jul 2013 13:45:04 -0700 (PDT) X-Received: by 10.49.35.225 with SMTP id l1mr1307232qej.1.1375130704131; Mon, 29 Jul 2013 13:45:04 -0700 (PDT) Newsgroups: comp.os.msdos.djgpp Date: Mon, 29 Jul 2013 13:45:03 -0700 (PDT) Complaints-To: groups-abuse AT google DOT com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=2.173.191.8; posting-account=v5xbdQoAAAAOGc9Ccc-kLZyobvPlN3Qr NNTP-Posting-Host: 2.173.191.8 User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <21e77579-1a40-4442-8111-fc976fba78fc@googlegroups.com> Subject: _CRT0_FLAG_NULLOK From: Georg Potthast Injection-Date: Mon, 29 Jul 2013 20:45:04 +0000 Content-Type: text/plain; charset=ISO-8859-1 Bytes: 1791 Lines: 14 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com I got my program to work fine in real mode DOS now when I set this flag: int _crt0_startup_flags = _CRT0_FLAG_NULLOK | _CRT0_FLAG_FILL_SBRK_MEMORY; Without this line above it crashes when executing "atoi" in these lines: const char* testchar = NULL; int testint = atoi(testchar); printf("testint:%d\n",testint); I thought if I initialize a pointer to NULL I avoid problems like that. In my program I call a library function which returns NULL if it cannot read the requested value. I shortend this to testchar = NULL in the snippet above. When I set the _crt0_startup_flags like above the variable testint gets the value zero. But is there a danger that the pointer could override memory, e.g. part of the operating system? Or why should I avoid _CRT0_FLAG_NULLOK ? Georg