Portability issues

Portability Issues

The purpose of this article is to collect portability issues often encountered by roguelike programmers as well as possible solutions for these problems.

Memory

• Some Operating Systems, such as Irix, allow the programs to read from a NULL address, while others will segfault instantly. Trying to write to a NULL address will hopefully always cause a segfault. (Except on many embedded systems. The Gameboy Advance, for example, will not segfault on a NULL address write.)

Display

• Only the characters of the basic (7bit) ASCII character set are reasonably portable. Using characters from extended character sets (like the solid blocks from the IBM DOS character set) or characters which aren't classified as printable by the ASCII standard (like the smileys from IBM DOS) will probably cause problems.
  • Extensions to ASCII are not portable. Unicode is portable, though, plus it includes all the old IBM DOS characters, though not necessarily at the same code points.

Filesystem

• Some Operating Systems (such as any derive from or copy Unix, or follow the POSIX standards) are case-sensitive as far as filenames are concerned. Others (like DOS or Windows) aren't. Still others (like Mac OS X) are inconsistent in their case-sensitivity or preservation. So, one shouldn't rely on any one case behavior for maximum portability.
• There are Operating Systems that forbide using certain characters in the file names.
• Operating Systems also can restrict the length of the filename or the total length of absolute path of file.
• DOS and Windows use different path separator character.a backslash ("\"). rather than the slash ("/") character defined in POSIX.
• Note that most modern operating systems allow files with spaces in them. This means if you pass arguments to another program you should be able to protect those arguments if they may contain spaces. Ie, if a user names themselves "Foo Bar", your save file may be "Foo Bar.sav". On Windows, it is highly likely that your path will have a space in it.

Input

• Use of the Escape key should be avoided, because escape is a special character for many of the terminals that roguelikes are traditionally played on. These terminals sometimes must hold up an escape key to see if it should be processed or passed on, and that causes annoying delays in a user interface that uses Escape.

• Which characters are used to indicate the end of a line in text files is OS-specific. One has to be careful when parsing text files.

• Remember that there are more than one keyboard layout in the world. A lot of international keyboards have different mappings than the US version that most people take for granted. Shift-., for example, is ; on a Finnish keyboard and > on a US keyboard. See a survey on PreferredKeyControls

Mac OS X

• The current version of the standard Mac OS X terminal (Terminal.app) only supports 8 colors. Early versions of Mac OS X curses library did not support color at all.

DOS

• Filenames are limited to 8 characters + a 3 characters extension. Additionally filenames must not contain whitespace or DOS special characters.
• Memory in the processor's real mode is tight and inconveniently segmented. Later models had a variety of schemes available for accessing expanded memory or extended memory, but being maximally portable to this platform means using less than 640KB of RAM.