[Mesa-dev] [PATCH 6/7] glsl: Hide many classes local to individual .cpp files in anon namespaces.

[Kenneth Graunke]

On 09/20/2013 06:52 PM, Eric Anholt wrote:
> This gives the compiler the chance to inline and not export class symbols
> even in the absence of LTO.  Saves about 60kb on disk.

This is probably worth doing.
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

Another important reason for doing this is that it avoids name
collisions.  By default, classes have external linkage, which means that
if you compile two files together that both define classes with the same
name, bad things happen.  You might get link errors, or it might just
randomly link code against the wrong one, with no messages whatsoever.

See commit 5cadb3ef7e6c1a67c45b0fdb2b0c2c1a369a97d8 for a bit of history
where this was actually happening, and we had real bugs as a result.

However, this is also extremely irritating: it prevents you from doing:

(gdb) break builtin_builder::create_shader

Instead, you have to do:

(gdb) break (anonymous namespace)::builtin_builder::create_shader

I'm having a really hard time believing that gdb doesn't have a
better/shorter way of doing this, but I sure can't find one.

If all else fails, you can always resort to line numbers:
(gdb) break builtin_functions.cpp:599

Apparently, debugging with anonymous namespaces on MSVC is even worse.

The lack of 'static' for forcing internal linkage on classes is simply
maddening.