Re: deprecation of in-tree builds

[Eric Blake <eblake@redhat.com>]

On 3/23/20 8:32 AM, Stefan Hajnoczi wrote:

>>> We could also make configure actively warn if used in
>>> the source tree.
>>
>> This was discussed before. I think instead of annoying people with a
>> warning, rather configure should be changed to create a build dir if run
>> from source and have a Makefile in top dir that runs make -C builddir so
>> people don't have to care about this or change their ways and can continue
>> to run configure && make from source dir but you don't have to support
>> in-tree build. Then you can deprecate in-tree builds but supporting only
>> out-of-tree without this convenience would not just unnecessarily annoy
>> those who prefer working in a single tree but people (and apparently some
>> tools) expect sources to build with usual configure; make; make install so
>> that should be the minimum to support.
> 
> Yes, please!  I use in-tree builds and find it tedious to cd into a
> build dir manually.
> 
> Also, many build scripts (packaging, etc) we'll break if we simply
> remove in-tree builds.  I think make && make install should continue to
> work.

Here's what I'm using locally to let my finger memory of building 
in-tree work in spite of having done 'mkdir build; cd build; 
../configure ...'.  We'd still need glue code in configure itself to 
detect when it is being invoked in-tree to create a subdir build/ and 
such a forwarding file, but if we want in-tree to FEEL like it works 
(even though it uses a build dir under the hood), it's certainly worth 
considering.

$ cat GNUmakefile
# Hack for redirecting while reminding myself to use distinct builddir
ifeq ($(MAKECMDGOALS),)
recurse: all
endif
.NOTPARALLEL: %
%: force
	@echo 'changing dir to build for $(MAKE) "$(MAKECMDGOALS)"...'
	@$(MAKE) -C build -f Makefile $(MAKECMDGOALS)
force: ;
.PHONY: force
GNUmakefile: ;


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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