Nikolai Pretzell wrote:


Jens-Heiner Rechtien schrieb:
 > Jan Holesovsky wrote:
 >> On Monday 18 December 2006 11:46, Thorsten Behrens wrote:
 > Kai Backman wrote:
>>>> Aah. Let me rephrase. Are -you- really sure the external include guard >>>> optimization provides enough benefit on all the compilers we are using
 >>>> to make it worthwhile to degrade readability by adding noise?

 >>> ok, seems we've deadlocked here. ;-)

 >>> Point is, the vast majority of the code uses that idiom as of today,
 >>> and I'm reluctant to advice people of the contrary
 >>> [...]
 >>> - if people think it's ok to start removing external
 >>> header guards right now (because it will take years to clean them up
 >>> anyway), I'd be fine with that, too.
 >>
 >> I hate them that much that I am willing to do a script that would do
 >> the removal ;-)
 >>
 >> What is the platform/compiler that probably needs this, please?  Any
 >> volunteer to do a comparison of the "with" and "without" compilation
 >> times?
 >
 > The one remaining compiler is Microsoft Visual
 > Studio. There are varying reports if this compiler has a build-in
 > "include guard optimization" or not.

According to Oliver Bolte, in version 8, the MSVC compiler uses the trick to connect a define (of an internal include guard) with the correlating header, which is one possble way to implement this, but v.7 does not.


Anyway, I would go with Thorstens remark: We will need years to remove the existing external include guards anyway. IMHO there is no significant performance gain by adding more of them now.

So my
Suggestion
----------
is: From today on, we use internal include guards only.
Until this has a measurable effect on our build times, we will use a newer version of MSVC.

What do you think?

i would appreciate this decision as well and would change the cppumaker accordingly if we will do it this way in the future.

Maybe someone has time to create a clever script to remove the external guards via script in minutes ;-)

Juergen


Nikolai

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