Re: [PATCH] remove warning for --host without --build

[Eric Blake]

On 04/23/2012 06:17 AM, Peter Rosin wrote:
>> So, in this case, configure has detected that it can run programs,
>> and therefore AC_RUN_IFELSE invocations will run the test program.
>> This is more reliable than relying on the 4th argument of AC_RUN_IFELSE,
>> which is most often a (pessimistic or optimistic) guess.
>> Therefore this outcome of $cross_compiling is DESIRABLE, not "wrong".
> 
> Oh, but it is wrong, it is a cross compile.  Claiming anything else
> is just delusional.  You can argue that the *effect* is desirable or
> not all you like, but a cross it is.

It _IS_ a cross-compile, but in the special subset of cross-compiles
that also happen to be executable from the host.  And this opens up all
sorts of problems where running the executable in a non-native
environment gives outright confusing results (such as thinking that
mingw supports symlinks).  But that generally boils down to the bug of
the person invoking configure lying about their environment, and not
something intrinsically bad with our cross-compilation hueristics.  And
the set of platforms where a cross-compilation allows native execution
is small enough that we already tend to recognize such bug reports
(you're compiling for mingw but using cygwin? did you use the right
arguments?), whether or not the user paid attention to the warning from
configure.

>>
>> Sure it is possible to write non-portable code and non-portable unit tests.
>> But this is irrelevant to a discussion about --build and --host.
> 
> And I think it's relevant.  Your proposed change leads to silent
> differences depending on e.g. the presence of Wine.

A cross-compilation environment where wine lets you run mingw binaries
is slightly different from a cross-compilation environment where
everything has to be guessed; both environments are interesting, to
different sets of users.  Maybe you are right that a knob to force
build!=host mode even when the non-native binaries can be run, in order
to use that knob to eliminate the surprises due to Wine, is worth
adding; further patches will probably be welcome, but probably post-2.69
material (I'm already late enough on the release as it is).

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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