Re: [PATCH] Makefile: Allow define overrides by prepending, not appending, CFLAGS

Hello everyone, And thanks Stefano for the patch! On Wed, 2022-09-14 at 15:45 +0200, Stefano Brivio wrote:

If we append CFLAGS to the ones passed via command line (if any), -D options we append will override -D options passed on command line (if any).

For example, OpenSUSE build flags include -D_FORTIFY_SOURCE=3, and we want to have -D_FORTIFY_SOURCE=2, if and only if not overridden. The current behaviour implies we redefine _FORTIFY_SOURCE as 2, though.

Instead of appending CFLAGS, prepend them by adding all the default build flags to another variable, a simply expanded one (defined with :=), named FLAGS, and pass that *before* CFLAGS in targets, so that defines from command line can override default flags.

Right. In fact, in openSUSE, we try to use _FORTIFY_SOURCE=3 for all the packages, although opting out is possible, if that causes problem or is undesirable for whatever reason. Point is though, that we would like for the CFLAGS that we set from the project configuration in OBS, to be the ones that are actually used. With this patch, this is exactly what happens, as we can see here: [ 31s] + CFLAGS='-O2 -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 - fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables - fstack-clash-protection -Werror=return-type -flto=auto -g' ... [ 32s] cc -Wall -Wextra -pedantic -std=c99 -D_XOPEN_SOURCE=700 - D_GNU_SOURCE -D_FORTIFY_SOURCE=2 -O2 -pie -fPIE -DPAGE_SIZE=4096 - DNETNS_RUN_DIR=\"/run/netns\" -DPASST_AUDIT_ARCH=AUDIT_ARCH_X86_64 - DRLIMIT_STACK_VAL=8192 -DARCH=\"X86_64\" -DHAS_SND_WND - DHAS_BYTES_ACKED -DHAS_MIN_RTT -DHAS_GETRANDOM -fstack-protector-strong -O2 -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -fstack-protector- strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash- protection -Werror=return-type -flto=auto -g qrap.c -o qrap -flto=auto Which is in fact what I want. So I guess the patch can have...

Reported-by: Dario Faggioli Signed-off-by: Stefano Brivio

... Tested-by: Dario Faggioli (If that's useful :-). AFAICS, the patch is not yet committed. I've therefore added it as a downstream one in my passt package on OBS: https://build.opensuse.org/package/show/home:dfaggioli:devel/passt I've also submitted the package to the Virtualization:containers Devel Project: https://build.opensuse.org/request/show/1005013 https://en.opensuse.org/openSUSE:Factory_development_model https://en.opensuse.org/openSUSE:How_to_contribute_to_Factory If/When it's accepted there, I'll proceed and file a request for putting it in "Factory", which will then mean that it will be available in openSUSE Tumbleweed's official repository. Thanks again and Regards -- Dario Faggioli, Ph.D http://about.me/dario.faggioli Virtualization Software Engineer SUSE Labs, SUSE https://www.suse.com/ ------------------------------------------------------------------- <> (Raistlin Majere)