Far be it for me to encourage over-use of preprocessor macros, but the ability of the preprocessor to embed file, function and line information makes it useful for debug trace. The use of the standard built-in NDEBUG macro allows the code to be automatically excluded on release builds.
Note that the lack of a comma between `"%s::%s(%d)"` and `format` is deliberate. It prints a formatted string with source location prepended.
For many systems with critical timing it is often useful to also include a timestamp using a suitable system-wide clock source, but since that is system dependent I have omitted that option from the example. Note that where timing is critical you should ensure that your stdout implementation is buffered and non-blocking.
Support for variadic macros may not be universal hacing been standardised in C99.
#if defined NDEBUG #define TRACE( format, ... )#else #define TRACE( format, ... ) printf( "%s::%s(%d) " format, __FILE__, __FUNCTION__, __LINE__, __VA_ARGS__ )#endif// Example usagevoid example(){ unsigned var = 0xdeadbeef ; TRACE( "var=0x%x", var ) ;}// Resultant output example:// example.c::example(5) var=0xdeadbeef//
