[Developers] proposal to turn off C++ automatictemplateinstantiation by default

[Erik Schnetter]

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On Tuesday 06 July 2004 11:25, Werner Benger wrote:
> On Tue, Jul 06, 2004 at 11:13:29AM +0200, Erik Schnetter wrote:
> > What you can always to is give the C++ compiler flags by hand when
> > you configure.  This overrides what Cactus chooses.  That means
> > that you as thorn author cannot decide, but that the people who
> > install the thorn can decide.  This is important, because the
> > decision on which compiler flags to use is system dependent, and if
> > someone want to use a C++ thorn on a machine that Cactus (or your
> > makefile) does not know, the user can still make things work.
>
> That's not the same: overriding during configure forces all thorns to
> use the same flags. What about the case if someone wants to use e.g.
> DAGH (which apparently doesn't like implicit templates) with one of
> our thorns (which don't work without implicit templates)? I just
> remember there were some issues with DAGH and FlexIO.

DAGH needs the same set of flags, -ptused and -no_auto_include.

I used both DAGH and FlexIO at the same time.  The problems that I 
remember were with both using the same macro names for different 
purposes.  Of course, both are C++ libraries and should not have been 
using macros in the first place, or at least stay within a defined name 
space.  Both were imperfect in this respect.

> > Apart from that this seems to be a theoretical decision.  Out of
> > four people encountering the problem, four have independently
> > chosen the same solution.  We can assume that there is some
> > generality.
>
> Depends if this DAGH is still in use and if it has these same issues
> as I seem to remember.

It is, but it hasn't.

> Apart from that, having the ability to have a 
> local thorn to override global settings locally in a systematic way
> doesn't appear to be a bad idea; I could have needed this some time
> ago. For instance, some thorn could enable or disable special
> optimizations for a certain architecture if this one is known to the
> thorn author.

That issue is unrelated to template instantiation.

- -erik

- -- 
Erik Schnetter <schnetter at aei.mpg.de>   http://www.aei.mpg.de/~eschnett/

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