Re: [dpdk-dev] [EXT] Re: [PATCH v4 1/5] mk: introduce helper to check valid compiler argument

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

On Mon, 2019-01-14 at 12:35 +0100, Thomas Monjalon wrote:
> -------------------------------------------------------------------
> ---
> 09/01/2019 11:39, Pavan Nikhilesh Bhagavatula:
> > From: Jerin Jacob <jerinj@marvell.com>
> > 
> > Introduce rte_cc_has_argument() Makefile helper to
> > check a given argument is support by the compiler.
> > 
> > Example Usage:
> > 
> > include $(RTE_SDK)/mk/rte.helper.mk
> > MACHINE_CFLAGS += $(call rte_cc_has_argument, -mcpu=octeontx2)
> > 
> > This would allow adding -mcpu=octeontx2 in MACHINE_CFLAGS
> > if it is only supported by the compiler. The use case for such
> > scheme is to enable the mcpu optimization if the compiler
> > supports else it needs to compile the source code without
> > any errors.
> > 
> > This patch also moves inclusion of toolchain's rte.vars.mk
> > to before the machine's rte.vars.mk inclusion to make
> > correct CC available for the cross compile case.
> > 
> > Signed-off-by: Jerin Jacob <jerinj@marvell.com>
> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> > ---
> > --- /dev/null
> > +++ b/mk/rte.helper.mk
> > @@ -0,0 +1,12 @@
> > +# SPDX-License-Identifier: BSD-3-Clause
> > +# Copyright(c) 2018 Marvell International Ltd
> > +
> > +# rte_cc_has_argument
> > +# Usage: MACHINE_CFLAGS += $(call rte_cc_has_argument, -mno-
> > avx512f)
> > +# Return the argument if the argument is supported by the
> > compiler.
> > +#
> > +define rte_cc_has_argument
> > +	$(shell $(CC) -Werror $(1) -c -x c /dev/null -o tmp$$ 2>
> > /dev/null && rm -f tmp$$ && echo $(1) | xargs echo -n)
> > +endef
> 
> What is tmp$$ ?

It is created per process with pid value.

> 
> If the command is interrupted in the middle, temp file is not
> cleaned.

Yes. I think we can move to RTE_OUTPUT. Even it is not cleaned 
then it is file, I think, that would be easiest solution.

> We could fix it with "trap".

Can we do it in Makefile? 

> Is it possible to just avoid creating a temporary file?

I tried it but gcc creates one.

> 
> 
>