[sr #108405] False negative for $cross_compiling when cross-compiling on Linux for Windows.

[Jehan]

URL:
  <http://savannah.gnu.org/support/?108405>

                 Summary: False negative for $cross_compiling when
cross-compiling on Linux for Windows.
                 Project: Autoconf
            Submitted by: jehan_zemarmot
            Submitted on: Wed 02 Oct 2013 06:27:00 AM GMT
                Category: None
                Priority: 5 - Normal
                Severity: 3 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:

If --host is set, and --build is not set, the current autoconf would make a
test program run and if it succeeds, it considers we are not cross-compiling.

Well this fails on a Linux mint with Wine installed by default (and probably
Ubuntu, and likely even any Debian and derivative). Indeed by default, Wine
would automatically handle any Windows executable (without the user even
asking explicitly). I have done the test by copying the conftest.exe generated
by autoconf and running "./conftest.exe", and... it succeeds without an error
and with $? = 0.

The workaround to this right now is to run as a super-user:
$ update-binfmts --disable wine

Or else to specify both --host and --build in the ./configure line, but I find
this being really inconvenient, whereas config.guess works awesomely well to
do this job. And this is just a relics from the past, in my opinion.

Anyway I believe Debian and derivative are quite common nowadays, and this
makes this false negative $cross_compiling quite annoying.

Of course it could be argued that if Wine were able to perform all the tests,
this is all just good. But actually Wine often fails to perform more
complicated tests (for instance I discovered this issue when compiling GTK+,
and it passed the basic cross-compiling test, but not the bigger glib-test),
and also the value of $cross_compiling is often tested for other usage in
projects' configure.ac and Makefile.am (for instance in GTK+, once again).

So I propose the attached patch. Basically if --host is set, but not --build,
once the the finale $host and $build values are set, processed and modified by
config.guess and config.sub, we check if there are any different, and we don't
make the run test in this specific case because its result may not be relevant
to tell whether we are really cross-compiling.



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File Attachments:


-------------------------------------------------------
Date: Wed 02 Oct 2013 06:27:00 AM GMT  Name:
0001-cross-compiling-handling-modern-platforms-able-to-ru.patch  Size: 2kB  
By: jehan_zemarmot

<http://savannah.gnu.org/support/download.php?file_id=29281>

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