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Hello,
On Thu, 8 Aug 2013, Simon Horman wrote:
> When building ipvsadm this allows make to add to CFLAGS supplied
> on the command line.
Hm, the change below simply adds -I, variable
override is already possible before the change. Is the
commit correct?
> This seems to make sense as Makefile and libipvs/Makefile
> add different CFLAGS but it may be desirable to supply supplementary
> flags when building ipvsadm.
>
> In particular the following may be useful when building ipvsadm
> on Debian Jessie.
>
> make CFLAGS='-I/usr/include/libnl3' LIBS='-lnl-3 -lnl-genl-3 -lnl-3 -lpopt'
Hm, such command line vars override the
vars in Makefiles, they do not add to them. So, it is
not good for libipvs where -fPIC is the difference.
make has such rules for vars:
Order of variables:
- command line
- makefile
- environment
For example: var=env make var=command_line
If -e is provided order is: command line, environment, makefile
Sub-make: only command line and environment vars are inherited,
use 'export' to provide variables defined in makefile
As result, we can support EXTRA_CFLAGS when
we want to add -Idir or other options, for example:
Makefile:
CFLAGS = $(EXTRA_CFLAGS) -Wall -Wunused -Wstrict-prototypes -g
libipvs/Makefile:
CFLAGS = $(EXTRA_CFLAGS) -Wall -Wunused -Wstrict-prototypes -g -fPIC
Then:
1. Add to CFLAGS by providing EXTRA_CFLAGS, override LIBS:
make EXTRA_CFLAGS='-I/usr/include/libnl3' \
LIBS='-lnl-3 -lnl-genl-3 -lnl-3 -lpopt'
2. Override CFLAGS for both Makefiles because CFLAGS from
command line is inherited in sub-make
make CFLAGS='-I/usr/include/libnl3 -fPIC' \
LIBS='-lnl-3 -lnl-genl-3 -lnl-3 -lpopt'
We can add EXTRA_LIBS if needed to complement
EXTRA_CFLAGS.
Also, this is NOT an alternative:
Makefile:
CFLAGS+=-Wall -Wunused -Wstrict-prototypes -g
Makefile:
CFLAGS+=-Wall -Wunused -Wstrict-prototypes -g -fPIC
because make CFLAGS=... will override the var,
makefile can override command line vars in such way but
it is ugly:
override var=DEFERRED
override var:=IMMEDIATE
override var+=APPEND
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
> ---
> Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 6e36d79..c8c1eec 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -48,7 +48,7 @@ STATIC_LIBS = libipvs/libipvs.a
> ifeq "${ARCH}" "sparc64"
> CFLAGS = -Wall -Wunused -Wstrict-prototypes -g -m64 -pipe
> -mcpu=ultrasparc -mcmodel=medlow
> else
> - CFLAGS = -Wall -Wunused -Wstrict-prototypes -g
> + CFLAGS = -I/usr/include/libnl3 -Wall -Wunused -Wstrict-prototypes -g
> endif
>
>
> --
> 1.8.3.2
Regards
--
Julian Anastasov <ja@xxxxxx>
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