Re: Modules, installing Squid headers, and src layout

On tor, 2007-10-11 at 20:17 -0600, Alex Rousskov wrote:
> Hello,
>
> To support loadable modules, we may need to alter Squid sources layout
> or installation procedure. This email discusses the problem and four
> possible solutions. Please review and suggest the best path forward.

Possibly, but I prefer not supporting loadable modules except where
there is very well defined boundaries.

> While it is possible for a module to use headers and libraries from
> Squid sources, doing so is a big and dangerous hack -- the sources are
> not designed to be used externally and may be in an inconsistent state,
> leading to unusable modules or, worse, subtle bugs.

Very true.

> AFAIK, the solution is for Squid to _install_ everything that a module
> may needed. Since a module may manipulate many Squid objects, this
> implies that Squid should install all header files (and possibly many
> libraries). Currently, Squid does not install any headers.

Only headers which have been cleaned up to a level of providing a stable
interface should be exported for use by external modules.

> The alternative is to install headers in /usr/local/squid/include/squid
> directory (note squid at the end). Modules will include such headers as
> "squid/foo.h", virtually eliminating the possibility of a conflict. We
> use this approach with other projects, and it works well.

Yes.

> Unfortunately for Squid, its code would also have to refer to its
> headers using the "squid/foo.h" pattern.

That's fine. The headers that are candidates for this should be cleaned
up to a level that they provide a stable interface, and moved to
include/squid/

> As you know, current header
> files are in in a "squid" directory. They are in "src". We could move
> all files from "src" to "src/squid". We use that design in Factory
> projects and it works well. However, CVS will lose all commit history if
> we move the files!

It's relatively easy to move files preserving history if that's
important. But given my preference on what may be candidates for use by
external modules I am not sure it matters much..

Regards
Henrik