Re: [PATCH] Add wcharP.h to hide internal wchar functions [BZ #18822]

[Florian Weimer <fweimer at redhat dot com>]

On 12/12/2017 12:40 AM, Joseph Myers wrote:
> On Mon, 11 Dec 2017, Florian Weimer wrote:
>
> > We should enhance the toolchain to do this kind of optimization automatically
> > (maybe using LTO?).  Or find another way to implement the markup in a more
>
> glibc makes use of being written as "C with ABI boundaries" - that is,
> code does things that are undefined in C for the program as a whole, but
> defined on the basis that each separate translation unit must implement
> the semantics of the functions therein in a way that would be valid for
> any valid caller.  I think supporting LTO for glibc would be hard.

Certainly for some parts of the library.  But not for high-level 
routines such as fnmatch or wcsxfrm_l.

Anyway, the point I was trying to make is that some optimizations need 
to happen at the compiler or linker level, otherwise the maintenance 
burden is too costly.  Functions in the public API already need to be 
declared in three places in many cases, and I think it's unwise to add 
an arbitrary number of architecture-specific header files into the mix.

> > It's also not clear why you need to replicate ___atribute_pure__ in those
> > declarations.
>
> Generally, an internal header can avoid repeating a function prototype
> using typeof, but typeof does not copy attributes, so making an internal
> declaration share the attributes of a public declaration requires
> duplicating them in both places.

I thought that these attributes were cumulative, so attribute_hidden 
would just be added to the attributes declared in include/wchar.h for 
those internal aliases.

Florian