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Date:   Mon, 14 Sep 2020 11:13:13 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Quentin Monnet <quentin@...valent.com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH bpf-next] bpftool: fix build failure

On Mon, Sep 14, 2020 at 11:06 AM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 9/14/20 10:55 AM, Andrii Nakryiko wrote:
> > On Mon, Sep 14, 2020 at 10:46 AM Yonghong Song <yhs@...com> wrote:
> >>
> >>
> >>
> >> On 9/14/20 10:23 AM, Quentin Monnet wrote:
> >>> On 14/09/2020 17:54, Yonghong Song wrote:
> >>>>
> >>>>
> >>>> On 9/14/20 9:46 AM, Yonghong Song wrote:
> >>>>>
> >>>>>
> >>>>> On 9/14/20 1:16 AM, Quentin Monnet wrote:
> >>>>>> On 14/09/2020 07:12, Yonghong Song wrote:
> >>>>>>> When building bpf selftests like
> >>>>>>>      make -C tools/testing/selftests/bpf -j20
> >>>>>>> I hit the following errors:
> >>>>>>>      ...
> >>>>>>>      GEN
> >>>>>>> /net-next/tools/testing/selftests/bpf/tools/build/bpftool/Documentation/bpftool-gen.8
> >>>>>>>
> >>>>>>>      <stdin>:75: (WARNING/2) Block quote ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:71: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:85: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:57: (WARNING/2) Block quote ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:66: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:109: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:175: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      <stdin>:273: (WARNING/2) Literal block ends without a blank line;
> >>>>>>> unexpected unindent.
> >>>>>>>      make[1]: ***
> >>>>>>> [/net-next/tools/testing/selftests/bpf/tools/build/bpftool/Documentation/bpftool-perf.8]
> >>>>>>> Error 12
> >>>>>>>      make[1]: *** Waiting for unfinished jobs....
> >>>>>>>      make[1]: ***
> >>>>>>> [/net-next/tools/testing/selftests/bpf/tools/build/bpftool/Documentation/bpftool-iter.8]
> >>>>>>> Error 12
> >>>>>>>      make[1]: ***
> >>>>>>> [/net-next/tools/testing/selftests/bpf/tools/build/bpftool/Documentation/bpftool-struct_ops.8]
> >>>>>>> Error 12
> >>>>>>>      ...
> >>>>>>>
> >>>>>>> I am using:
> >>>>>>>      -bash-4.4$ rst2man --version
> >>>>>>>      rst2man (Docutils 0.11 [repository], Python 2.7.5, on linux2)
> >>>>>>>      -bash-4.4$
> >>>>>>>
> >>>>>>> Looks like that particular version of rst2man prefers to have a
> >>>>>>> blank line
> >>>>>>> after literal blocks. This patch added block lines in related .rst
> >>>>>>> files
> >>>>>>> and compilation can then pass.
> >>>>>>>
> >>>>>>> Cc: Quentin Monnet <quentin@...valent.com>
> >>>>>>> Fixes: 18841da98100 ("tools: bpftool: Automate generation for "SEE
> >>>>>>> ALSO" sections in man pages")
> >>>>>>> Signed-off-by: Yonghong Song <yhs@...com>
> >>>>>>
> >>>>>>
> >>>>>> Hi Yonghong, thanks for the fix! I didn't see those warnings on my
> >>>>>> setup. For the record my rst2man version is:
> >>>>>>
> >>>>>>       rst2man (Docutils 0.16 [release], Python 3.8.2, on linux)
> >>>>>>
> >>>>>> Your patch looks good, but instead of having blank lines at the end of
> >>>>>> most files, could you please check if the following works?
> >>>>>
> >>>>> Thanks for the tip! I looked at the generated output again. My above
> >>>>> fix can silent the warning, but certainly not correct.
> >>>>>
> >>>>> With the following change, I captured the intermediate result of the
> >>>>> .rst file.
> >>>>>
> >>>>>     ifndef RST2MAN_DEP
> >>>>>            $(error "rst2man not found, but required to generate man pages")
> >>>>>     endif
> >>>>> -       $(QUIET_GEN)( cat $< ; echo -n $(call see_also,$<) ) | rst2man
> >>>>> $(RST2MAN_OPTS) > $@
> >>>>> +       $(QUIET_GEN)( cat $< ; echo -n $(call see_also,$<) ) | tee
> >>>>> /tmp/tt | rst2man $(RST2MAN_OPTS) > $@
> >>>>>
> >>>>> With below command,
> >>>>>       make clean && make bpftool-cgroup.8
> >>>>> I can get the new .rst file for bpftool-cgroup.
> >>>>>
> >>>>> At the end of file /tmp/tt (changed bpftool-cgroup.rst), I see
> >>>>>
> >>>>>        ID       AttachType      AttachFlags     Name
> >>>>> \n SEE ALSO\n========\n\t**bpf**\ (2),\n\t**bpf-helpers**\
> >>>>> (7),\n\t**bpftool**\ (8),\n\t**bpftool-btf**\
> >>>>> (8),\n\t**bpftool-feature**\ (8),\n\t**bpftool-gen**\
> >>>>> (8),\n\t**bpftool-iter**\ (8),\n\t**bpftool-link**\
> >>>>> (8),\n\t**bpftool-map**\ (8),\n\t**bpftool-net**\
> >>>>> (8),\n\t**bpftool-perf**\ (8),\n\t**bpftool-prog**\
> >>>>> (8),\n\t**bpftool-struct_ops**\ (8)\n
> >>>>>
> >>>>> This sounds correct if we rst2man can successfully transforms '\n'
> >>>>> or '\t' to proper encoding in the man page.
> >>>>>
> >>>>> Unfortunately, with my version of rst2man, I got
> >>>>>
> >>>>> .IP "System Message: WARNING/2 (<stdin>:, line 146)"
> >>>>> Literal block ends without a blank line; unexpected unindent.
> >>>>> .sp
> >>>>> n SEE
> >>>>> ALSOn========nt**bpf**(2),nt**bpf\-helpers**(7),nt**bpftool**(8),nt**bpftool\-btf**(8),nt**bpftool\-feature**(8),nt**bpftool\-gen**(8),nt**bpftool\-iter**(8),nt**bpftool\-link**(8),nt**bpftool\-map**(8),nt**bpftool\-net**(8),nt**bpftool\-perf**(8),nt**bpftool\-prog**(8),nt**bpftool\-struct_ops**(8)n
> >>>>>
> >>>>> .\" Generated by docutils manpage writer.
> >>>>>
> >>>>> The rst2man simply considered \n as 'n'. The same for '\t' and
> >>>>> this caused the issue.
> >>>>>
> >>>>> I did not find a way to fix the problem https://urldefense.proofpoint.com/v2/url?u=https-3A__www.google.com_url-3Fq-3Dhttps-3A__zoom.us_j_94864957378-3Fpwd-253DbXFRL1ZaRUxTbDVKcm9uRitpTXgyUT09-26sa-3DD-26source-3Dcalendar-26ust-3D1600532408208000-26usg-3DAOvVaw3SJ0i8oz4ZM-2DGRb7hYkrYlyet&d=DwIDaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=kEK7ScPMF-y-i8dli-or8wWEGREW5V4qPB7UqHqDnkg&s=Br0g0MFXxL_pJuDVTOY5UrmvfD2ru_6Uf_X_8Nr2Rhk&e= .
> >>>>
> >>>> The following change works for me.
> >>>>
> >>>> @@ -44,7 +44,7 @@ $(OUTPUT)%.8: %.rst
> >>>>    ifndef RST2MAN_DEP
> >>>>           $(error "rst2man not found, but required to generate man pages")
> >>>>    endif
> >>>> -       $(QUIET_GEN)( cat $< ; echo -n $(call see_also,$<) ) | rst2man
> >>>> $(RST2MAN_OPTS) > $@
> >>>> +       $(QUIET_GEN)( cat $< ; echo -e $(call see_also,$<) ) | rst2man
> >>>> $(RST2MAN_OPTS) > $@
> >>>>
> >>>>    clean: helpers-clean
> >>>>           $(call QUIET_CLEAN, Documentation)
> >>>> -bash-4.4$
> >>>>
> >>>> I will send revision 2 shortly.
> >>>
> >>> Thanks Yonghong, but this does not work on my setup :/. The version of
> >>> echo which is called on my machine from the Makefile does not seem to
> >>> interpret the "-e" option and writes something like "-e\nSEE ALSO",
> >>> which causes rst2man to complain.
> >>>
> >>> I suspect the portable option here would be printf, even though Andrii
> >>> had some concerns that we could pass a format specifier through the file
> >>> names [0].
> >>>
> >>> Would this work on your setup?
> >>>
> >>>        $(QUIET_GEN)( cat $< ; printf $(call see_also,$<) ) | rst2man...
> >>>
> >>> Would that be acceptable?
> >>
> >> It works for me. Andrii originally suggested `echo -e`, but since `echo
> >> -e` does not work in your environment let us use printf then. I will add
> >> a comment about '%' in the bpftool man page name.
> >
> > It's amazing how incompatible echo can be. But that aside, I have
> > nothing against printf itself, but:
> >
> > printf "%s" "whatever we want to print out"
> >
> > seems like the way to go, similarly how you'd do it in your C code, no?
>
> This won't really work :-(
>
> -bash-4.4$ printf "%s" "\n\n"
> \n\n-bash-4.4$ printf "\n\n"
>
>
> -bash-4.4$
>
> Looks like "\n" needs to be in format string to make a difference.
>

I just learned that %b was added specifically for that case:

$ printf "%b" "\n\n"


$

>
> >
> >>
> >>>
> >>> [0]
> >>> https://lore.kernel.org/bpf/ca595fd6-e807-ac8e-f15f-68bfc7b7dbc4@isovalent.com/T/#m01bb298fd512121edd5e77a26ed5382c0c53939e
> >>>
> >>> Quentin
> >>>

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