linux-kernel - Re: [PATCH v3 03/68] selftests: Compile with -D_GNU

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Date: Thu, 9 May 2024 14:25:29 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Edward Liaw <edliaw@...gle.com>, shuah@...nel.org,
 Mickaël Salaün <mic@...ikod.net>,
 Günther Noack <gnoack@...gle.com>,
 Christian Brauner <brauner@...nel.org>,
 Richard Cochran <richardcochran@...il.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 kernel-team@...roid.com, linux-security-module@...r.kernel.org,
 netdev@...r.kernel.org, linux-riscv@...ts.infradead.org, bpf@...r.kernel.org
Subject: Re: [PATCH v3 03/68] selftests: Compile with -D_GNU_SOURCE when
 including lib.mk

On 5/9/24 12:57 PM, Edward Liaw wrote:
> lib.mk will add -D_GNU_SOURCE to CFLAGS by default.  This will make it
> unnecessary to add #define _GNU_SOURCE in the source code.
> 
> Fixes: 809216233555 ("selftests/harness: remove use of LINE_MAX")
> Suggested-by: John Hubbard <jhubbard@...dia.com>
> Signed-off-by: Edward Liaw <edliaw@...gle.com>
> ---
>   tools/testing/selftests/Makefile | 4 ++--
>   tools/testing/selftests/lib.mk   | 5 ++++-
>   2 files changed, 6 insertions(+), 3 deletions(-)
>

Hi Edward,

This looks good, with one small refactoring opportunity remaining, though:

> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index f0431e6cb67e..9039f3709aff 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -170,11 +170,11 @@ ifneq ($(KBUILD_OUTPUT),)
>     # $(realpath ...) resolves symlinks
>     abs_objtree := $(realpath $(abs_objtree))
>     BUILD := $(abs_objtree)/kselftest
> -  KHDR_INCLUDES := -D_GNU_SOURCE -isystem ${abs_objtree}/usr/include
> +  KHDR_INCLUDES := -isystem ${abs_objtree}/usr/include
>   else
>     BUILD := $(CURDIR)
>     abs_srctree := $(shell cd $(top_srcdir) && pwd)
> -  KHDR_INCLUDES := -D_GNU_SOURCE -isystem ${abs_srctree}/usr/include
> +  KHDR_INCLUDES := -isystem ${abs_srctree}/usr/include

As mentioned in [1] (but there are a lot of patches to manage here, and
I think it got overlooked), you could factor out the duplicated
-D_GNU_SOURCE items into a single place:

[1] 
https://lore.kernel.org/all/ac8c217e-4109-4ca7-a7dd-fc4fc8b0a4de@nvidia.com/

thanks,
-- 
John Hubbard
NVIDIA

>     DEFAULT_INSTALL_HDR_PATH := 1
>   endif
>   
> diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
> index 3023e0e2f58f..e782f4c96aee 100644
> --- a/tools/testing/selftests/lib.mk
> +++ b/tools/testing/selftests/lib.mk
> @@ -67,7 +67,7 @@ MAKEFLAGS += --no-print-directory
>   endif
>   
>   ifeq ($(KHDR_INCLUDES),)
> -KHDR_INCLUDES := -D_GNU_SOURCE -isystem $(top_srcdir)/usr/include
> +KHDR_INCLUDES := -isystem $(top_srcdir)/usr/include
>   endif
>   
>   # In order to use newer items that haven't yet been added to the user's system
> @@ -188,6 +188,9 @@ endef
>   clean: $(if $(TEST_GEN_MODS_DIR),clean_mods_dir)
>   	$(CLEAN)
>   
> +# Build with _GNU_SOURCE by default
> +CFLAGS += -D_GNU_SOURCE
> +
>   # Enables to extend CFLAGS and LDFLAGS from command line, e.g.
>   # make USERCFLAGS=-Werror USERLDFLAGS=-static
>   CFLAGS += $(USERCFLAGS)