[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [Libvir] using gnulib: starting with the physmem and getaddrinfo modules



"Daniel P. Berrange" <berrange redhat com> wrote:
...
>> include "physmem.h".  For getaddrinfo, merely include "getaddrinfo.h"
>> from the two files that use the function.

Hi Dan,

> I've not looked closely, but since we're unconditiaonlly including
> it, I assume the getaddrinfo.h file is setup to not override the
> existing definition of getaddrinfo if the local OS has it.

Yes, it works :-)
getaddrinfo.h is provided by the gnulib module, so it's always present.
As far as I know, no system provides /usr/include/getaddrinfo.h,
so there's no risk of masking some existing definition there.

>> This change brings in a lot of code, but many of the lib/.[ch] files
>> are used only on systems that lack some required functionality.  For
>> example, the getaddrinfo.c file isn't even compiled when it's not
>> needed.
>>
>> In the patch below, I've included a new script called bootstrap.
>> It is a wrapper around gnulib-tool that pulls into libvirt the
>> files selected by the (currently two) modules in use.  Those new
>> files go in three places:
>>
>>   m4/*.m4
>>   lib/*.[ch] and a few template .h.in files
>>   gl-tests/ for unit test C programs and Bourne shell scripts

Actually, you indicated preference for the above directory names.
I'm happy that you think differently, now :-)

> I think the source code should go into  gnulib/*.[ch]  in case we
> ever want to have a lib/ dir for code shared by the daemon & library.
> There's no need to pollute the top level dir with gl-tests, when we
> can have  tests/gnulib/, or  gnulib/tests/.  We've already got an m4/
> directory, so we might as well use that (or a m4/gnulib, or gnulib/m4
> subdir).

>> However, note that gettextize and libtoolize (run by autogen.sh)
>> also deposit many *.m4 files in m4.  I compared and found that 8
>> of the files that are already pulled in by the *ize programs are
>> also pulled in (potentially newer versions) from gnulib.  But currently,
>> using gettext-0.16.1 or gettext-0.17, there is no difference in any
>> of the overlapping files.
>
> This sounds like the trickiest issue. We currently run both of those
> tools using --force, so they overwrite any existing files present in
> the local tree. IIRC libtoolize shouldn't touch the m4/ directory,
> but gettextize (or rather autopoint) definitely does.

Actually, libtoolize does.  e.g., m4/libtool.m4 and m4/lt*.m4.

...
>> Running bootstrap creates the new lib/ and gl-tests/ directories.
>
> I don't want a dependancy on a script pulling in files from another random
> project that we have to grab from the internet.
>
>> Personally, I prefer not to add generated files to version control
>> systems, because it can lead to problems with version skew if all
>> developers don't use the same releases of the tools that do the
>> generating.  Perhaps more importantly, when there are massive diffs in
>> the generated files, that can obscure real changes in non-generated parts
>> of the code.  That already happens to me whenever the .po files change.
>
> Given a fresh CVS checkout of libvirt & fresh Fedora/RHEL/etc OS
> install one should be able to do a full build without requiring extra
> code checkouts from unrelated projects. Since gnulib is only distributed
> in source form, and not available from the OS package manager, the
> only viable approach is to commit the GNULib files to CVS.
...
By "viable" surely you mean: "viable for libvirt" :-)

As I said, I am happy to do it whichever way you guys prefer.
My next patch will include cvs-adding all of the pulled-in files,
but will leave the existing m4/ directory and not cvs-add all of
the files added by gettextize and libtoolize.

> IMHO, this *reduces* the problem of version skew, because it doesn't
> rely on each developer getting the same copy of gnulib. We can update

In my experience, getting the right copy of gnulib matters far less than
using recent enough versions of autoconf, automake, libtool, gettext.
*unless* you're the person who just reported that snprintf (or the
function of the week) segfaults under unusual conditions when run
on some old version of e.g., HP/UX.

> the in-CVS copy of the gnulib bits we care about as & when we need them
> and know everyone has the same bits. If gnulib really is as stable as
> its said to be, then we won't be seeing frequent massive diffs - we'll
> just have minor additions as we find more portability modules we need.

Right.

>> But if people prefer to add all of these imported files to CVS, just
>> say the word and I'll prepare the patch.  If so, do you guys want the
>> gettextize- and libtoolize-added files to be version-controlled, now, too?
>
> So the gettextize script copies its stuff into m4/ when you run the autogen
> script. We need to make sure the gnulib stuff in CVS takes priority over
> stuff added by gettextize.  Does aclocal  have any kind of ordering when
> you give it multiple include paths with -I arg. eg would
>
>
>    'aclocal -I m4/ -I gnulib/m4'
>
> ensure correct prioritization ?

Looks like it.  I'll confirm.

> Another option if we  go with the idea of having gnulib stuff in a subdir
> like gnulib/m4/*.m4, would be to change autogen.sh to do
>
>    autopoint --force
>    cp -f gnulib/m4/*.m4 m4/
>
> ie, always use the top-level m4/ directory as a scratch area for stuff we
> don't commit to CVS, but that is used when creating configure.in.
>
> On the other hand, this means the released tar.gz would have 2 copies
> of the m4, so a 3rd option is to just remove the --force arg from autopoint
> and let the gnulib stuff naturally take priority by virtue of already existing
> on disk when autopoint is run.

I like the idea of keeping the m4 directories separate.
Will follow up with a proposal.


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]