True and False in the C Programming Language

I know, C is dead, right? Not quite. While C has been supplanted in many industries by C++, C#, and other object-oriented languages, much of the automotive industry still relies on plain vanilla C - MISRA C, to be specific. I overheard the following question today: "should TRUE be set to !FALSE or should it be set to 1 - which is more MISRA compliant?" I don't know which is more MISRA compliant (off the top of my head), but I'd like to offer an alternative that, to my thinking, is more type-safe and avoids clashes with the macro definitions provided with many compilers.

Since C does not have native support for a Boolean type, it is common to #define TRUE and FALSE:

#define FALSE 0

#define TRUE !FALSE

FALSE is always zero and true may be any non-zero integer, so it is safest to let the pre-compiler decide what !FALSE means. This is portable but not type-safe; TRUE and FALSE may be compared to a result of any type (leaving the type conversion to the compiler). I like to use a typedef'd enumeration, instead:

typedef enum {eFALSE = 0; eTRUE;} BOOL_t;

Since this is "user defined", it is incompatible with the return type of standard library functions, so they must either be handled in the typical manner or with explicit casts.

Thinking about how to define and use boolean types in C reveals an important lesson about the "safe" use of C. That is: Avoid comparisons to TRUE (or eTRUE or whatever). Since zero will always be "false", comparisons with FALSE will always work.

Fitting a Round Peg into a Square Hole

I received an iPod nano for Christmas. It's just what I wanted but I was not looking forward to moving the 400+ albums I had in Windows Media Player - complete with album art - into iTunes. My anxiety was warranted: the result was a disaster. So, I took the opportunity to completely re-rip my entire CD library into iTunes. I chose to keep working with the mp3 format but bumped up the resolution from 128 kbps to 192 kbps. I must say that iTunes seems to do a slightly better job of finding album art than WMP, though I still found many albums for which I had to manually paste an image (either found on the web or scanned from the original).