[Development] Using #pragma once

[Thiago Macieira]

On Monday, 8 October 2018 09:12:26 PDT Matthew Woehlke wrote:
> On 08/10/2018 02.23, Henry Skoglund wrote:
> > So, what about a new preprocessor command:
> > 
> > __has_same_md6_digest
> 
> See also http://wg21.link/p0538 and note that EWG rejected it. The
> general consensus, AFAICT, is that modules is expected to make all this
> stuff irrelevant, and therefore EWG does not want to invest in fiddling
> with the preprocessor for a problem that is becoming irrelevant.

Comparing hashes has another problem: what happens if you have /usr/include/
QtCore/qglobal.h but it's slightly different (an older version)? In that case, 
it could get included by #pragma once but wouldn't be for regular include 
guards.

Again, this is a mistake in setting things up, but it happens often enough. 
And the problem is one of figuring out what's wrong.

Not that it would stop *another* header from the older installation from 
getting included, though.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center