Re: [PATCH v2 02/13] cppcheck: Split out essential defines into a BASE_CPPFLAGS variable

[Laurent Vivier <lvivier@redhat.com>]

On 4/21/26 05:23, David Gibson wrote:
> Our cppcheck target need certain flags from the compiler so that they it
> can analyse the code correctly.  Currently we extract these rather

"so that it can analyze"

> awkwardly from FLAGS / CFLAGS / CPPFLAGS.  But this means we inhibit one
> of cppcheck's features: by default it will attempt to analyse paths for all
> combinations of compile time options, not just a single one.
> 
> Analysing *all* paths doesn't work for us because many of the -D options we
> use are essential to compile at all, so unless we supply those to cppcheck,
> overriding the default behaviour we get many spurious errors.  At the
> moment, however, we give cppcheck *all* our -D options, including
> conditional / configurable ones, not just the essential ones.
> 
> All cppcheck really needs here is those essential -D options.  Split those
> into a separate variable, and use that directly rather than the clunky
> $(filter) expression.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Laurent Vivier <lvivier@redhat.com>

> ---
>   Makefile | 14 ++++++++------
>   1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 17e70d22..0de98375 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -30,11 +30,15 @@ ifeq ($(shell $(CC) -O2 -dM -E - < /dev/null 2>&1 | grep ' _FORTIFY_SOURCE ' > /
>   FORTIFY_FLAG := -D_FORTIFY_SOURCE=2
>   endif
>   
> +# Require preprocessor flags we can't build without
> +BASE_CPPFLAGS := -D_XOPEN_SOURCE=700 -D_GNU_SOURCE \
> +	-DPAGE_SIZE=$(shell getconf PAGE_SIZE) \
> +	-DVERSION=\"$(VERSION)\"
> +
>   FLAGS := -Wall -Wextra -Wno-format-zero-length -Wformat-security
> -FLAGS += -pedantic -std=c11 -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
> +FLAGS += -pedantic -std=c11
>   FLAGS +=  $(FORTIFY_FLAG) -O2 -pie -fPIE
> -FLAGS += -DPAGE_SIZE=$(shell getconf PAGE_SIZE)
> -FLAGS += -DVERSION=\"$(VERSION)\"
> +FLAGS += $(BASE_CPPFLAGS)
>   FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
>   
>   PASST_SRCS = arch.c arp.c bitmap.c checksum.c conf.c dhcp.c dhcpv6.c \
> @@ -195,6 +199,4 @@ CPPCHECK_FLAGS = --std=c11 --error-exitcode=1 --enable=all --force	\
>   	 -D CPPCHECK_6936
>   
>   cppcheck: $(PASST_SRCS) $(HEADERS)
> -	$(CPPCHECK) $(CPPCHECK_FLAGS) 					\
> -		$(filter -D%,$(FLAGS) $(CFLAGS) $(CPPFLAGS)) $^		\
> -		$^
> +	$(CPPCHECK) $(CPPCHECK_FLAGS) $(BASE_CPPFLAGS) $^