From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 29 Jun 2013 13:56:57 +0000 (+0100)
Subject: Eliminate the `rlimits.h' header using scary macros.
X-Git-Tag: 1.3.7~14
X-Git-Url: https://git.distorted.org.uk/~mdw/fwd/commitdiff_plain/1cd4a3bfdaf82f0bc0691671954b239dccb003fb?hp=1cd4a3bfdaf82f0bc0691671954b239dccb003fb

Eliminate the `rlimits.h' header using scary macros.

The `rlimits.h' header is a bit of a hack, which was thought necessary
because if must assemble a list of things conditionally.  This patch
eliminates this unpleasantness by replacing it with a different hack
which is at least as nasty.

Associate with each potential limit name a macro whose value is either
`t' or `nil', indicating whether the limit is known.  This can be done
using lots of `#ifdef ... #else ... #endif' blocks.  Finally, assemble
a list macro of all of the names, whether they're known or not (because
we can't tell at this point).  The trick is that, instead of just calling
`_(...)' for each item, we call `MAYBE_CALL(_, HAVE_???_P, (...))', and
the latter uses token-pasting to dispatch on the `HAVE_???_P' flag and
conditionally invoke `_(...)'.  Thus callers can work with this as a
conventional list macro.

Of course, building all of this is monumentally tedious, so we get Emacs
to do it for us.
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