Re: Global constants

[Martin Hunt <hunt at redhat dot com>]

On Mon, 2006-02-13 at 14:28 -0500, Frank Ch. Eigler wrote:

> The standard syscalls tapset should define such constants, so end-user
> scripts do not have to.

Hien and I are currently rewriting the syscall tapset, so if constants
get implemented soon, we can make immediate use of them.  


> If read-only-ness of these globals is important, then a new "const"
> keyword would indeed come in handy.  (I'd promptly reuse it as a
> qualifier for embedded-C functions that are declared to have no
> side-effects.)  I would implement this angle by a new flag on vardecl,
> enforced non-lvalueness during elaboration or translation, rather than
> whole new staptree.h classes.

Declaring variables readonly reduces the probe complexity by removing
the global locks around all variable access. So it clearly seems like a
win. 

Also it would be nice to have a way to declare these constants in
embedded C, so we can use the C header files to get the values, rather
than look them up.

something like
%{ const_O_CREAT = O_CREAT; %}
  instead of
O_CREAT = 64