C Portability Lessons from Weird Machines
A lot of the "weird machines" for C are microcontrollers and the like; the 8051 is mentioned, but another big "C-hostile" MCU family is the Microchip PIC, which still has its own C compiler. DSPs are another category where unusual word sizes are common (24 bits for char/short/int is often encountered.)<p><i>It’s amazing that, by carefully writing portable ANSI C code and sticking to standard library functions, you can create a program that will compile and work without modification on almost any of these weird systems.</i><p>The big question, which I ask whenever someone harps on about portability, is <i>does it even make sense</i>? Is your average PC/smartphone application realistically ever going to be ported to a 6502 or a Unisys mainframe? Keep in mind that I/O in particular is going to differ significantly, and something like standard input might not even exist (think of a fixed-function device like an oven controller with only a few buttons and LEDs for I/O.) I don't think it's particularly amazing, because the "core" of C essentially represents all the functionality of a stored-program digital computer; so if you completely ignore things like I/O it's not hard to see how the same piece of code can express the same concepts on <i>any</i> of the latter type of computer.<p>It should also be noted that these "weird" environments are often not "strictly conforming" either, because it's either impossible or doesn't really make sense to. Besides the "omissions" they will also have "extensions" that help the programmer to more fully utilise the platform's capabilities.