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Comment by jzelinskie | Hacker News Reader

After reading the source, I realized that I have no idea what modern, idiomatic C looks like. There are tons of uses of #define, some even in the middle of typedefs. I'm pretty sure a whole queue data structure is defined in macros in vqueue.h. Is this normal?

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From vqueue.h header:

It's very much based on this:

http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/sys/queue.h?anno...

Not very modern, in other words.

C does not have generics or templates so macroses are the only way to define data structures and algorithms over arbitrary types without repetition. Linux kernel uses macroses to define some data structures. Many other projects do the same.

Whether that is normal or not, it's up to developer. It's possible to use as small subset of C++ as developer wants. E.g. use only templates. But staying in C realm might be better for portability.

> C does not have generics or templates so macroses

When I read this, I couldn't help but think of "macroses" as pronounced like "neuroses", which seems appropriate.

Pretty normal for the BSD kernels. A lot of the very basic datastructures are defined as macros. For instance, here's queue.h: https://svnweb.freebsd.org/base/head/sys/sys/queue.h?revisio...

While not 100% necessary, header macros to implement lists, queues (and even trees, see: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/sys/sys/tree.h?...) are common in C.

They first appear for kernel usage where the fact that they expanded to inline code in functions avoided creating too many stack-frames and provided optimization.

They do have the advantage of not relying on casting everything to "void *" or resort to callbacks for walking (see: TAILQ_FOREACH for instance).

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