netdev - Re: [PATCH bpf-next] bpftool: Remove redundant slashes

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Date:   Fri, 25 Feb 2022 22:09:10 -0800
From:   Song Liu <song@...nel.org>
To:     Yuntao Wang <ytcoode@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Mauricio Vásquez <mauricio@...volk.io>,
        Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpftool: Remove redundant slashes

On Fri, Feb 25, 2022 at 8:15 AM Yuntao Wang <ytcoode@...il.com> wrote:
>
> Since the _OUTPUT variable holds a value ending with a trailing slash,

While the change makes sense, I think the description here is not accurate.
Currently, we require OUTPUT to end with trailing slash. However, if
OUTPUT is not defined, _OUTPUT will not hold a trailing slash. Adding
trailing slash to _OUTPUT is one part of this patch, so I think we should not
say that's the reason of this change.

Thanks,
Song

> there is no need to add another one when defining BOOTSTRAP_OUTPUT and
> LIBBPF_OUTPUT variables.
>
> When defining LIBBPF_INCLUDE and LIBBPF_BOOTSTRAP_INCLUDE, we shouldn't
> add an extra slash either for the same reason.
>
> When building libbpf, the value of the DESTDIR argument should also not
> end with a trailing slash.
>
> Signed-off-by: Yuntao Wang <ytcoode@...il.com>
> ---
>  tools/bpf/bpftool/Makefile | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index ba647aede0d6..9800f966fd51 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -18,19 +18,19 @@ BPF_DIR = $(srctree)/tools/lib/bpf
>  ifneq ($(OUTPUT),)
>    _OUTPUT := $(OUTPUT)
>  else
> -  _OUTPUT := $(CURDIR)
> +  _OUTPUT := $(CURDIR)/
>  endif
> -BOOTSTRAP_OUTPUT := $(_OUTPUT)/bootstrap/
> +BOOTSTRAP_OUTPUT := $(_OUTPUT)bootstrap/
>
> -LIBBPF_OUTPUT := $(_OUTPUT)/libbpf/
> +LIBBPF_OUTPUT := $(_OUTPUT)libbpf/
>  LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
> -LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
> +LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)include
>  LIBBPF_HDRS_DIR := $(LIBBPF_INCLUDE)/bpf
>  LIBBPF := $(LIBBPF_OUTPUT)libbpf.a
>
>  LIBBPF_BOOTSTRAP_OUTPUT := $(BOOTSTRAP_OUTPUT)libbpf/
>  LIBBPF_BOOTSTRAP_DESTDIR := $(LIBBPF_BOOTSTRAP_OUTPUT)
> -LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)/include
> +LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)include
>  LIBBPF_BOOTSTRAP_HDRS_DIR := $(LIBBPF_BOOTSTRAP_INCLUDE)/bpf
>  LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
>
> @@ -44,7 +44,7 @@ $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DI
>
>  $(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
>         $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_OUTPUT) \
> -               DESTDIR=$(LIBBPF_DESTDIR) prefix= $(LIBBPF) install_headers
> +               DESTDIR=$(LIBBPF_DESTDIR:/=) prefix= $(LIBBPF) install_headers
>
>  $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_DIR)
>         $(call QUIET_INSTALL, $@)
> @@ -52,7 +52,7 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_
>
>  $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
>         $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
> -               DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
> +               DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR:/=) prefix= \
>                 ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
>
>  $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
> --
> 2.35.1
>