[llvm] r230812 - Discourage in-source autoconf builds (as we already do for the cmake build)

[Jonathan Roelofs]

On 2/28/15 11:01 PM, Nick Lewycky wrote:
> Eric Christopher wrote:
>>
>>
>> On Sat, Feb 28, 2015 at 11:45 AM Nick Lewycky <nicholas at mxc.ca
>> <mailto:nicholas at mxc.ca>> wrote:
>>
>>     Jonathan Roelofs wrote:
>>      > Author: jroelofs
>>      > Date: Fri Feb 27 17:35:47 2015
>>      > New Revision: 230812
>>      >
>>      > URL: http://llvm.org/viewvc/llvm- project?rev=230812&view=rev
>>     <http://llvm.org/viewvc/llvm-project?rev=230812&view=rev>
>>      > Log:
>>      > Discourage in-source autoconf builds (as we already do for the
>>     cmake build)
>>
>>     I have reverted this patch. Please explain yourselves.
>>
>>
>> Pretty rude way of putting it but sure.
>
> Hey, sorry. I was upset, and neither of you deserved that sort of tone.
> I'm truly sorry, and thank you for taking the time to write an
> explanation in spite of my poor attitude!
Sorry about my end of this too. I had assumed there was consensus on 
this from discussing it on #llvm. I probably should have mailed the list 
first explaining what I had intended to do.
>
>> Best practices.
>>
>> https://www.sourceware.org/autobook/autobook/autobook_14.html#SEC14
>>
>> In general you want to keep your source directory pristine (readonly)
>> and configuring inside the source directory is fraught with problems.
+1

This is a small step toward allowing the source dir to be kept readonly 
during builds.
>
> Got it.
>
> If it matters, I've been using this configuration for a long time, and I
> haven't seen any glitch for years, though I do remember a time when that
> wasn't true. I understand why it risks continuing problems.
>
> The two main things I get from in-tree builds are that I can grep
> through the source including the generated source,
This one you can work around (somewhat) by doing a 
subdirectory-of-source build, i.e.:

   $ svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
   $ mkdir -p llvm/build && cd llvm/build
   $ ../configure [options]

> and that I can rename
> the directory trees. Out of tree builds bake in a directory name.
Doesn't this just mean that renames have to happen in two steps (i.e. 
rename the src version of the dir, then rename the build version of the 
dir)? Or is there something fundamentally different here that I'm missing?
> I can
> try this again and see whether it's still a problem, or if there's
> something we can fix here.
>
>> This also ensures that the occasional report I get of someone not being
>> able to do a make distclean in the source directory will go away. I will
>> also take a working make distclean if you'd like to do that instead
>> (though, obviously, I'd prefer the current patch).
>
> Reducing support burden is a perfectly reasonable reason. As someone who
> uses this configuration, I find that I very rarely run make clean and
> don't think I've tried make distclean. I would not be surprised to learn
> that I've accidentally learned to avoid the things that don't work.
>
> As you've probably already surmised, I'm not super interested in writing
> a patch that fixes "make distclean". :) Which I guess means that you can
:) Especially with the whole "autotools is going away once we have 
feature parity with the cmake build" push.
> ignore me and un-revert? I do have one review comment though, please
> change the error message from "discouraged" to "are no longer
> supported". In part, I was confused by the combination of the term
> discouragement (in the error message and in the commit log) with a hard
> error.
Sorry about that... how about "In-source builds are not allowed. Please 
configure from a separate build directory."? This would better match the 
message printed by the cmake build in this situation.


Cheers,

Jon
>
> Nick
>
>>
>> -eric
>>
>>
>>      >
>>      > http://reviews.llvm.org/D7961
>>      >
>>      > Modified:
>>      >      llvm/trunk/autoconf/configure. ac <http://configure.ac>
>>      >      llvm/trunk/configure
>>      >
>>      > Modified: llvm/trunk/autoconf/configure. ac <http://configure.ac>
>>      > URL: http://llvm.org/viewvc/llvm- project/llvm/trunk/autoconf/
>>     configure.ac?rev=230812&r1= 230811&r2=230812&view=diff
>>
>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/autoconf/configure.ac?rev=230812&r1=230811&r2=230812&view=diff>
>>
>>      > ============================== ==============================
>>     ==================
>>      > --- llvm/trunk/autoconf/configure. ac <http://configure.ac>
>>     (original)
>>      > +++ llvm/trunk/autoconf/configure. ac <http://configure.ac> Fri
>>     Feb 27 17:35:47 2015
>>      > @@ -73,6 +73,11 @@ if test ${srcdir} != "." ; then
>>      >     fi
>>      >   fi
>>      >
>>      > +dnl Quit if it is an in-source build
>>      > +if test ${srcdir} == "." ; then
>>      > +  AC_MSG_ERROR([In-source builds are discouraged. Configure from
>>     a separate build directory.])
>>      > +fi
>>      > +
>>      >   dnl Default to empty (i.e. assigning the null string to) CFLAGS
>>     and CXXFLAGS,
>>      >   dnl instead of the autoconf default (for example, '-g -O2' for
>>     CC=gcc).
>>      >   : ${CFLAGS=}
>>      >
>>      > Modified: llvm/trunk/configure
>>      > URL: http://llvm.org/viewvc/llvm- project/llvm/trunk/configure?
>>     rev=230812&r1=230811&r2= 230812&view=diff
>>
>> <http://llvm.org/viewvc/llvm-project/llvm/trunk/configure?rev=230812&r1=230811&r2=230812&view=diff>
>>
>>      > ============================== ==============================
>>     ==================
>>      > --- llvm/trunk/configure (original)
>>      > +++ llvm/trunk/configure Fri Feb 27 17:35:47 2015
>>      > @@ -1999,6 +1999,12 @@ echo "$as_me: error: Already configured
>>      >     fi
>>      >   fi
>>      >
>>      > +if test ${srcdir} == "." ; then
>>      > +  { { echo "$as_me:$LINENO: error: In-source builds are
>>     discouraged. Configure from a separate build directory.">&5
>>      > +echo "$as_me: error: In-source builds are discouraged. Configure
>>     from a separate build directory.">&2;}
>>      > +   { (exit 1); exit 1; }; }
>>      > +fi
>>      > +
>>      >   : ${CFLAGS=}
>>      >   : ${CXXFLAGS=}
>>      >
>>      >
>>      >
>>      > ______________________________ _________________
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>>     <http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits>
>>      >
>>
>

-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded