Annoying warning, a.k.a. how to add to CFLAGS

Annoying warning, a.k.a. how to add to CFLAGS

[Ian Zimmerman]

When I checkout current master, run ./tools/configurator/configurator >
config.h and then make, I get exactly 1 warning for the whole thing:

ccan/strgrp/strgrp.c: In function ‘grp_for’:
ccan/strgrp/strgrp.c:296:0: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
     #pragma omp parallel for schedule(dynamic)

I figured out that I can silence that by adding -fopenmp to my CFLAGS.
But how to do that permanently?  I don't want to specify that on the
command line every time, and I also don't want to set it in the
environment because sometimes I compile other things than ccan ;-)

Is there a reason why this is not in the master Makefile?

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Re: Annoying warning, a.k.a. how to add to CFLAGS

[David Gibson]

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On Thu, Aug 31, 2017 at 08:23:50PM -0700, Ian Zimmerman wrote:
> When I checkout current master, run ./tools/configurator/configurator >
> config.h and then make, I get exactly 1 warning for the whole thing:
> 
> ccan/strgrp/strgrp.c: In function ‘grp_for’:
> ccan/strgrp/strgrp.c:296:0: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
>      #pragma omp parallel for schedule(dynamic)
> 
> I figured out that I can silence that by adding -fopenmp to my CFLAGS.
> But how to do that permanently?  I don't want to specify that on the
> command line every time, and I also don't want to set it in the
> environment because sometimes I compile other things than ccan ;-)
> 
> Is there a reason why this is not in the master Makefile?

Because working out how to make module specific CFLAGS additions in
the Makefile isn't entirely trivial.  Working out how to do so in a
reasonably portable fashion is even harder - I don't expect -fopenmp
will work for all compilers, so applying it there would change a
cosmetic warning into a compile failure.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: Annoying warning, a.k.a. how to add to CFLAGS

[Rhys Ulerich]

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ccan/strgrp/strgrp.c: In function ‘grp_for’:
ccan/strgrp/strgrp.c:296:0: warning: ignoring #pragma omp parallel
[-Wunknown-pragmas]
     #pragma omp parallel for schedule(dynamic)


An ifdef might be added to the code:
https://stackoverflow.com/questions/1300180/ignore-openmp-on-machine-that-doesnt-have-it

- Rhys

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Re: Annoying warning, a.k.a. how to add to CFLAGS

[Rusty Russell]

Ian Zimmerman <itz@very.loosely.org> writes:
> When I checkout current master, run ./tools/configurator/configurator >
> config.h and then make, I get exactly 1 warning for the whole thing:
>
> ccan/strgrp/strgrp.c: In function ‘grp_for’:
> ccan/strgrp/strgrp.c:296:0: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
>      #pragma omp parallel for schedule(dynamic)
>
> I figured out that I can silence that by adding -fopenmp to my CFLAGS.
> But how to do that permanently?  I don't want to specify that on the
> command line every time, and I also don't want to set it in the
> environment because sometimes I compile other things than ccan ;-)

Hmm, well, if you're compiling strgrp, you should be adding CFLAGS
from _info, which sets this correctly.

In this case, we could just test defined(_OPENMP) instead of
HAVE_OPENMP, though, which would automagically work.

Module author CC'd

Cheers,
Rusty.



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Re: Annoying warning, a.k.a. how to add to CFLAGS

[Andrew Jeffery]

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On Mon, 2017-09-04 at 10:27 +0930, Rusty Russell wrote:
> > Ian Zimmerman <itz@very.loosely.org> writes:
> > When I checkout current master, run ./tools/configurator/configurator >
> > config.h and then make, I get exactly 1 warning for the whole thing:
> > 
> > ccan/strgrp/strgrp.c: In function ‘grp_for’:
> > ccan/strgrp/strgrp.c:296:0: warning: ignoring #pragma omp parallel [-Wunknown-pragmas]
> >      #pragma omp parallel for schedule(dynamic)
> > 
> > I figured out that I can silence that by adding -fopenmp to my CFLAGS.
> > But how to do that permanently?  I don't want to specify that on the
> > command line every time, and I also don't want to set it in the
> > environment because sometimes I compile other things than ccan ;-)
> 
> Hmm, well, if you're compiling strgrp, you should be adding CFLAGS
> from _info, which sets this correctly.
> 
> In this case, we could just test defined(_OPENMP) instead of
> HAVE_OPENMP, though, which would automagically work.

Yeah, I was never really happy with what I did with HAVE_OPENMP, and I
don't recall why I did it. I'd be happy with a patch implementing
Rusty's suggestion of #if defined(_OPENMP).

Andrew

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