[Xen-devel] Re: [RFC] build: use xargs in conjunction with etags

[Horms <horms@xxxxxxxxxxxx>]

[ Sorry if this is a duplicate, I had a problem with my mail client
  and I'm not sure where the previous incarntation went ]

In article <20060624062236.GA19117@xxxxxxxxxxxx> you wrote:
> On Fri, Jun 23, 2006 at 04:56:41PM +0200, Markus Armbruster wrote:
>> Horms <horms@xxxxxxxxxxxx> writes:
>> 
>> > The existing etags invocation does not seem to work for me,
>> > but using xargs in the same way that it is used for crats does.
>> > I'm pretty sure that is because on Debian etags == ctags,
>> > does anyone have etags lying around to test if this works?
>> >
>> > Also, I'm pretty sure this xargs approach will break for both ctags
>> > and etags if there are too many files to for one command line,
>> > as ctags/etags will be invoked multiple times, and the resulting
>> > tags file will only contain the tags for the last invocation.
>> >
>> > Signed-Off-By: Horms <horms@xxxxxxxxxxxx>
>> > --- x/xen/Makefile
>> > +++ x/xen/Makefile
>> > @@ -132,7 +136,7 @@ endef
>> >  
>> >  .PHONY: _TAGS
>> >  _TAGS: 
>> > -  $(all_sources) | etags -
>> > +  $(all_sources) | xargs etags
>> 
>> When xargs invokes etags more than once (i.e. it's actually needed),
>> each invocation will clobber the output of the previous one.
> 
> Indeed, I was concerned about that.
> 
>> To run
>> etags on an arbitrarily long file list, try something like
>> 
>>     rm -f TAGS && $(all_sources) | xargs etags -a
> 
> Is the rm -f TAGS neccessary?

On further research I see that -a means append, so yes the rm is
neccessary.

> I believe that for ctags the following will work. At least it seems
> to work just fine here with exuberant-ctags 5.5.4
> 
>       $(all_sources) | xargs ctags -L -

For the record, xargs should not be present in the above command line

        $(all_sources) | ctags -L -

However, the same syntax as etags can also be used, which is nice for
uniformity

        rm -f tags && $(all_sources) | xargs ctags -a

I will post a patch that uses the -a approach for both etags and ctags.
This should work for pretty much all systems. In particular I tested
debian, where ctags and etags are the same binary, and this approach
works because a TAGS file is produced when the binary is invoked as
etags, and a tags file is produced when the binary is invoked as etags.

-- 
Horms                                           
H: http://www.vergenet.net/~horms/          W: http://www.valinux.co.jp/en/


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