Re: [PATCH 3/6] libbpf: Initialize CFLAGS before including Makefile.include

[Ihor Solodrai]

On 3/23/26 8:40 AM, Leo Yan wrote:
> tools/scripts/Makefile.include may expand EXTRA_CFLAGS in a future
> change.  This could alter the initialization of CFLAGS, as the default
> options "-g -O2" would never be set once EXTRA_CFLAGS is expanded.
> 
> Prepare for this by moving the CFLAGS initialization before including
> tools/scripts/Makefile.include, so it is not affected by the extended
> EXTRA_CFLAGS.
> 
> Append EXTRA_CFLAGS to CFLAGS only after including Makefile.include and
> place it last so that the extra flags propagate properly and can
> override the default options.
> 
> tools/scripts/Makefile.include already appends $(CLANG_CROSS_FLAGS) to
> CFLAGS, the Makefile appends $(CLANG_CROSS_FLAGS) again, remove the
> redundant append.
> 
> Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
> ---
>  tools/lib/bpf/Makefile | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index 168140f8e6461bd06db40e23d21a3fb8847ccbf4..eca584fb061e16013e76827e4203f6be0477a73e 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -49,6 +49,14 @@ man_dir_SQ = '$(subst ','\'',$(man_dir))'
>  export man_dir man_dir_SQ INSTALL
>  export DESTDIR DESTDIR_SQ
>  
> +# Defer assigning EXTRA_CFLAGS to CFLAGS until after including
> +# tools/scripts/Makefile.include, as it may add flags to EXTRA_CFLAGS.
> +ifdef EXTRA_CFLAGS
> +  CFLAGS :=
> +else
> +  CFLAGS := -g -O2
> +endif
> +
>  include $(srctree)/tools/scripts/Makefile.include
>  
>  # copy a bit from Linux kbuild
> @@ -70,13 +78,6 @@ LIB_TARGET	= libbpf.a libbpf.so.$(LIBBPF_VERSION)
>  LIB_FILE	= libbpf.a libbpf.so*
>  PC_FILE		= libbpf.pc
>  
> -# Set compile option CFLAGS
> -ifdef EXTRA_CFLAGS
> -  CFLAGS := $(EXTRA_CFLAGS)
> -else
> -  CFLAGS := -g -O2
> -endif
> -
>  # Append required CFLAGS
>  override CFLAGS += -std=gnu89
>  override CFLAGS += $(EXTRA_WARNINGS) -Wno-switch-enum
> @@ -84,7 +85,7 @@ override CFLAGS += -Werror -Wall
>  override CFLAGS += $(INCLUDES)
>  override CFLAGS += -fvisibility=hidden
>  override CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
> -override CFLAGS += $(CLANG_CROSS_FLAGS)
> +override CFLAGS += $(EXTRA_CFLAGS)

Acked-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>

>  
>  # flags specific for shared library
>  SHLIB_FLAGS := -DSHARED -fPIC
>