[PATCH] DocBook: Avoid stdout junk with no man pages to compress

[PATCH] DocBook: Avoid stdout junk with no man pages to compress

[Ulf Magnusson]

gzip would run as 'gzip -f' when no uncompressed man pages were found,
making it compress the (empty) stdin to stdout.

A few alternative solutions:

  - 'find' with {} + might be speedier, but maybe that's not portable
    enough (though it's in POSIX 2001 at least AFAICS)

  - xargs --no-run-if-empty, but that's a GNU extension

  - Always discarding stdout, if it's unlikely to ever be helpful

  - More fancy stuff like the following, though maybe some of them could
    run into shell limits too, re. d56fcf299fb4 (DocBook: Do not exceed
    argument list limit)

    * A plain shell 'for' loop

    * mandocs: $(MAN)
      	if [ `find $(obj)/man -name '*.9' | wc -l` -gt 0 ]; then \
      		find $(obj)/man -name '*.9' | xargs gzip -f; \
      	fi

    * mandocs: $(MAN)
      	man_pages=`find $(obj)/man -name '*.9'`; \
      	if [ -n "$$man_pages" ]; then \
      		echo "$$man_pages" | xargs gzip -f; \
      	fi

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
---
 Documentation/DocBook/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
index b6a6a2e..73bddf7 100644
--- a/Documentation/DocBook/Makefile
+++ b/Documentation/DocBook/Makefile
@@ -56,7 +56,7 @@ htmldocs: $(HTML)
 
 MAN := $(patsubst %.xml, %.9, $(BOOKS))
 mandocs: $(MAN)
-	find $(obj)/man -name '*.9' | xargs gzip -f
+	find $(obj)/man -name '*.9' -exec gzip -f {} \;
 
 installmandocs: mandocs
 	mkdir -p /usr/local/man/man9/
-- 
2.1.4

Re: [PATCH] DocBook: Avoid stdout junk with no man pages to compress

[Jim Davis]

On Sun, Jul 12, 2015 at 2:59 PM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
> gzip would run as 'gzip -f' when no uncompressed man pages were found,
> making it compress the (empty) stdin to stdout.

> --- a/Documentation/DocBook/Makefile
> +++ b/Documentation/DocBook/Makefile
> @@ -56,7 +56,7 @@ htmldocs: $(HTML)
>
>  MAN := $(patsubst %.xml, %.9, $(BOOKS))
>  mandocs: $(MAN)
> -       find $(obj)/man -name '*.9' | xargs gzip -f
> +       find $(obj)/man -name '*.9' -exec gzip -f {} \;
>
>  installmandocs: mandocs
>         mkdir -p /usr/local/man/man9/

That does get rid of the binary burp, but 'xargs gzip -f'  has been in
the Makefile since January, and gzipping '\n' just started recently.
So what's changed?

It looks like, for whatever reason, make installmandocs always ends up
rerunning mandocs -- there's now a 'GEN  Documentation
Docbook//v4l2.xml' printed, and that extra mandocs invocation is where
the problematic second invocation of find is coming from.  I won't
pretend to understand the Makefile flow to guess at why that's
happening, but obviously 'make mandocs; make installmandocs' shouldn't
need to regenerate things already generated.

In any event,

Tested-by: Jim Davis <jim.epost@gmail.com>

Jim

Re: [PATCH] DocBook: Avoid stdout junk with no man pages to compress

[Ulf Magnusson]

On Sun, Jul 12, 2015 at 04:36:53PM -0700, Jim Davis wrote:
> On Sun, Jul 12, 2015 at 2:59 PM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
> > gzip would run as 'gzip -f' when no uncompressed man pages were found,
> > making it compress the (empty) stdin to stdout.
> 
> > --- a/Documentation/DocBook/Makefile
> > +++ b/Documentation/DocBook/Makefile
> > @@ -56,7 +56,7 @@ htmldocs: $(HTML)
> >
> >  MAN := $(patsubst %.xml, %.9, $(BOOKS))
> >  mandocs: $(MAN)
> > -       find $(obj)/man -name '*.9' | xargs gzip -f
> > +       find $(obj)/man -name '*.9' -exec gzip -f {} \;
> >
> >  installmandocs: mandocs
> >         mkdir -p /usr/local/man/man9/
> 
> That does get rid of the binary burp, but 'xargs gzip -f'  has been in
> the Makefile since January, and gzipping '\n' just started recently.
> So what's changed?
> 

No idea. I just assumed it had been broken since then, since the version
before d56fcf299fb4 (DocBook: Do not exceed argument list limit) looked
for *.9 files before running gzip:

mandocs: $(MAN)
	$(if $(wildcard $(obj)/man/*.9),gzip -f $(obj)/man/*.9)

> It looks like, for whatever reason, make installmandocs always ends up
> rerunning mandocs -- there's now a 'GEN  Documentation
> Docbook//v4l2.xml' printed, and that extra mandocs invocation is where
> the problematic second invocation of find is coming from.  I won't
> pretend to understand the Makefile flow to guess at why that's
> happening, but obviously 'make mandocs; make installmandocs' shouldn't
> need to regenerate things already generated.

I won't pretend to understand the Makefile flow either. Guess it might
be worth looking into v4l2.xml as well then. Could be some directory
shenanigans going on judging from the '//'.

> 
> In any event,
> 
> Tested-by: Jim Davis <jim.epost@gmail.com>
> 
> Jim

I just noticed the commit message only mentions the alternative
solutions and not the implemented solution. Could send a v2 that fixes
that, but I'll wait for more comments first.

Cheers,
Ulf

Re: [PATCH] DocBook: Avoid stdout junk with no man pages to compress

[Ulf Magnusson]

On Mon, Jul 13, 2015 at 2:46 AM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
> On Sun, Jul 12, 2015 at 04:36:53PM -0700, Jim Davis wrote:
>> On Sun, Jul 12, 2015 at 2:59 PM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
>> > gzip would run as 'gzip -f' when no uncompressed man pages were found,
>> > making it compress the (empty) stdin to stdout.
>>
>> > --- a/Documentation/DocBook/Makefile
>> > +++ b/Documentation/DocBook/Makefile
>> > @@ -56,7 +56,7 @@ htmldocs: $(HTML)
>> >
>> >  MAN := $(patsubst %.xml, %.9, $(BOOKS))
>> >  mandocs: $(MAN)
>> > -       find $(obj)/man -name '*.9' | xargs gzip -f
>> > +       find $(obj)/man -name '*.9' -exec gzip -f {} \;
>> >
>> >  installmandocs: mandocs
>> >         mkdir -p /usr/local/man/man9/
>>
>> That does get rid of the binary burp, but 'xargs gzip -f'  has been in
>> the Makefile since January, and gzipping '\n' just started recently.
>> So what's changed?
>>
>
> No idea. I just assumed it had been broken since then, since the version
> before d56fcf299fb4 (DocBook: Do not exceed argument list limit) looked
> for *.9 files before running gzip:
>
> mandocs: $(MAN)
>         $(if $(wildcard $(obj)/man/*.9),gzip -f $(obj)/man/*.9)
>
>> It looks like, for whatever reason, make installmandocs always ends up
>> rerunning mandocs -- there's now a 'GEN  Documentation
>> Docbook//v4l2.xml' printed, and that extra mandocs invocation is where
>> the problematic second invocation of find is coming from.  I won't
>> pretend to understand the Makefile flow to guess at why that's
>> happening, but obviously 'make mandocs; make installmandocs' shouldn't
>> need to regenerate things already generated.
>
> I won't pretend to understand the Makefile flow either. Guess it might
> be worth looking into v4l2.xml as well then. Could be some directory
> shenanigans going on judging from the '//'.
>

I looked into it some more, and I'm now fairly certain that 'mandocs' always
runs its recipe regardless of the status of the prerequisites. Changing the
top-level Makefile to do

        $(Q)$(MAKE) --debug=v $(build)=Documentation/DocBook $@

and running 'make mandocs', you see some FORCEs in the output, which -- unless
my make fu is weak -- causes all the targets above that to always be considered
out of date:

File 'mandocs' does not exist.
 Considering target file 'Documentation/DocBook/z8530book.9'.
   Considering target file 'Documentation/DocBook/z8530book.xml'.
     ...
     Considering target file 'FORCE'.
      File 'FORCE' does not exist.
      Finished prerequisites of target file 'FORCE'.
     Must remake target 'FORCE'.
     Successfully remade target file 'FORCE'.
     ...
   Must remake target 'Documentation/DocBook/z8530book.xml'.
 ...
Must remake target 'mandocs'.


Re. the 'GEN  Documentation Docbook//v4l2.xml', I think the problem is the
following rule in Documentation/DocBook/media/Makefile:

$(MEDIA_OBJ_DIR)/v4l2.xml: $(OBJIMGFILES)
        @$($(quiet)gen_xml)
        @(ln -sf `cd $(MEDIA_SRC_DIR) && /bin/pwd`/v4l/*xml $(MEDIA_OBJ_DIR)/)
        @(ln -sf `cd $(MEDIA_SRC_DIR) && /bin/pwd`/dvb/*xml $(MEDIA_OBJ_DIR)/)

./Documentation/DocBook/v4l2.xml is a symlink, so make compares the
modification time of the symlink *target* (which is never updated) against the
image (*.png, *.gif, etc.) files in $(OBJIMGFILES). Updating the symlink itself
won't change that modification time, so that's why it always runs.

Passing --check-symlink-times to make so that it also looks at the modification
time of the symlink seems to change a bunch of other stuff in the output too.
Maybe there's other problems lurking here as well.

>>
>> In any event,
>>
>> Tested-by: Jim Davis <jim.epost@gmail.com>
>>
>> Jim
>
> I just noticed the commit message only mentions the alternative
> solutions and not the implemented solution. Could send a v2 that fixes
> that, but I'll wait for more comments first.
>
> Cheers,
> Ulf

Cheers,
Ulf

Re: [PATCH] DocBook: Avoid stdout junk with no man pages to compress

[Ulf Magnusson]

On Tue, Jul 14, 2015 at 6:27 AM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
> On Mon, Jul 13, 2015 at 2:46 AM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
>> On Sun, Jul 12, 2015 at 04:36:53PM -0700, Jim Davis wrote:
>>> On Sun, Jul 12, 2015 at 2:59 PM, Ulf Magnusson <ulfalizer.lkml@gmail.com> wrote:
>>> > gzip would run as 'gzip -f' when no uncompressed man pages were found,
>>> > making it compress the (empty) stdin to stdout.
>>>
>>> > --- a/Documentation/DocBook/Makefile
>>> > +++ b/Documentation/DocBook/Makefile
>>> > @@ -56,7 +56,7 @@ htmldocs: $(HTML)
>>> >
>>> >  MAN := $(patsubst %.xml, %.9, $(BOOKS))
>>> >  mandocs: $(MAN)
>>> > -       find $(obj)/man -name '*.9' | xargs gzip -f
>>> > +       find $(obj)/man -name '*.9' -exec gzip -f {} \;
>>> >
>>> >  installmandocs: mandocs
>>> >         mkdir -p /usr/local/man/man9/
>>>
>>> That does get rid of the binary burp, but 'xargs gzip -f'  has been in
>>> the Makefile since January, and gzipping '\n' just started recently.
>>> So what's changed?
>>>
>>
>> No idea. I just assumed it had been broken since then, since the version
>> before d56fcf299fb4 (DocBook: Do not exceed argument list limit) looked
>> for *.9 files before running gzip:
>>
>> mandocs: $(MAN)
>>         $(if $(wildcard $(obj)/man/*.9),gzip -f $(obj)/man/*.9)
>>
>>> It looks like, for whatever reason, make installmandocs always ends up
>>> rerunning mandocs -- there's now a 'GEN  Documentation
>>> Docbook//v4l2.xml' printed, and that extra mandocs invocation is where
>>> the problematic second invocation of find is coming from.  I won't
>>> pretend to understand the Makefile flow to guess at why that's
>>> happening, but obviously 'make mandocs; make installmandocs' shouldn't
>>> need to regenerate things already generated.
>>
>> I won't pretend to understand the Makefile flow either. Guess it might
>> be worth looking into v4l2.xml as well then. Could be some directory
>> shenanigans going on judging from the '//'.
>>
>
> I looked into it some more, and I'm now fairly certain that 'mandocs' always
> runs its recipe regardless of the status of the prerequisites. Changing the
> top-level Makefile to do
>
>         $(Q)$(MAKE) --debug=v $(build)=Documentation/DocBook $@
>
> and running 'make mandocs', you see some FORCEs in the output, which -- unless
> my make fu is weak -- causes all the targets above that to always be considered
> out of date:
>
> File 'mandocs' does not exist.
>  Considering target file 'Documentation/DocBook/z8530book.9'.
>    Considering target file 'Documentation/DocBook/z8530book.xml'.
>      ...
>      Considering target file 'FORCE'.
>       File 'FORCE' does not exist.
>       Finished prerequisites of target file 'FORCE'.
>      Must remake target 'FORCE'.
>      Successfully remade target file 'FORCE'.
>      ...
>    Must remake target 'Documentation/DocBook/z8530book.xml'.
>  ...
> Must remake target 'mandocs'.

Had forgotten that 'mandocs' is a phony target too. That alone makes it always
run its recipe when it's a prerequisite of some target that's run.

>
>
> Re. the 'GEN  Documentation Docbook//v4l2.xml', I think the problem is the
> following rule in Documentation/DocBook/media/Makefile:
>
> $(MEDIA_OBJ_DIR)/v4l2.xml: $(OBJIMGFILES)
>         @$($(quiet)gen_xml)
>         @(ln -sf `cd $(MEDIA_SRC_DIR) && /bin/pwd`/v4l/*xml $(MEDIA_OBJ_DIR)/)
>         @(ln -sf `cd $(MEDIA_SRC_DIR) && /bin/pwd`/dvb/*xml $(MEDIA_OBJ_DIR)/)
>
> ./Documentation/DocBook/v4l2.xml is a symlink, so make compares the
> modification time of the symlink *target* (which is never updated) against the
> image (*.png, *.gif, etc.) files in $(OBJIMGFILES). Updating the symlink itself
> won't change that modification time, so that's why it always runs.
>
> Passing --check-symlink-times to make so that it also looks at the modification
> time of the symlink seems to change a bunch of other stuff in the output too.
> Maybe there's other problems lurking here as well.
>
>>>
>>> In any event,
>>>
>>> Tested-by: Jim Davis <jim.epost@gmail.com>
>>>
>>> Jim
>>
>> I just noticed the commit message only mentions the alternative
>> solutions and not the implemented solution. Could send a v2 that fixes
>> that, but I'll wait for more comments first.
>>
>> Cheers,
>> Ulf
>
> Cheers,
> Ulf

Cheers,
Ulf