You cannot have C code without macros. Period. One of the biggest shifts moving to C++ from C is letting the preprocessor take a back seat. Ya, it still has its place, but not like in C.
This one is ubiquitous in systems programming:
#ifndef BUF_SIZE /* Allow "cc -D" to override definition */
#define BUF_SIZE 1024
#endif
...
char buf[BUF_SIZE];
The above example utilizes the hot-swap nature of predefined macros to give us a constant without the overhead of memory allocation. I had to re-program myself to stop doing this in C++ codebases. C++ is all about const correctness and what better place to have a const that something like in the example below.
const size_t BuffSize = 1024;
char buf[BuffSize];
Of course there are a myriad of superior alternatives for array allocation in C++, not to mention the std::array class or better yet std::vector. But, I digress… Macros…
Glib is one of the most common libs in C. You get data structures, algorithms, and GObject for all your OOP needs. But, macros - Sweet Mary-Josephine are there some macros. Just look at a sampling of Glib. This is just a list of miscellaneous macros.
When defining custom GObjects there are convenience macros that leverage nested macros (i.e., my macros have macros). I have to keep jumping to definition just to remember what exactly is going on under these macros I am sprinkling all over my code. The convenience of macros expanding to generate class-like properties is no doubt awesome, but, hell… I need a giant cheat-sheet just to keep my ducks in a row.
On a separate non-rant, one of the lesser utilized features in C macros is the octothorp # as an eval tool. It’s not just for #defines anymore.
Check this out. Here we are going to do 2 things: print the passed in macro param and then evaluate said param.
#define Peval(cmd) printf(#cmd ": %g\n", cmd);
int main (int argc, char **argv)
{
double list[] = {1,2,3};
Peval(sizeof(list)/(sizeof(double)+0.0));
}
running this will output both the string to be evaluated and the evaluated string. Ya, I had to double-take that last sentence too. Trust me, it checks out.
// program output
sizeof(list)/(sizeof(double)+0.0): 3