Re: [Qemu-devel] [PATCH for-2.9] Fix check for target OS support

[Peter Maydell]

On 28 March 2017 at 12:53, Stefan Weil <address@hidden> wrote:
> Am 28.03.2017 um 10:04 schrieb Paolo Bonzini:
>> On 27/03/2017 22:11, Stefan Weil wrote:
>>> * Support cross compilation with the most common cross prefixes
>>>   for Mingw-w64. Other cross builds are still broken!
>> Can you explain how it's broken?  Why does check_define not work at this
>> point, for cross builds?
>>
>> "../configure --cross-prefix=x86_64-w64-mingw32-" seems to work for me.
>>
>> Paolo
>
> You are right. I was wrong because of this use case:
>
> $ ./configure '--enable-debug' '--cross-prefix=x86_64-w64-mingw32'
>
> ERROR: Unsupported host OS CYGWIN_NT-6.1
>
> So the error message is misleading when I specify a wrong cross prefix
> (it should have been x86_64-w64-mingw32- instead of x86_64-w64-mingw32).

Ah, I see. In the fall-through case we'd then complain that
the compiler didn't work. I think the underlying problem here
is that we use the compiler (for the check_prefix tests) before
the "does this compiler even work" test...

(This only happens in the case where you're doing a cross compile
and the build machine is not a supported QEMU host.)

> With the correct cross prefix, builds work, so cross builds are
> not a critical issue as I thought.
>
> The second issue which remains is calling ./configure --help:
>
> $ ./configure --help
>
> ERROR: Unsupported host OS CYGWIN_NT-6.1

Yeah, we should not complain for --help; I'll see if I can fix that.

> The third issue is the message for deprecated cpus or targets
> which should use "target" instead of "host".

We are not (yet) deprecating any targets, so we don't want to
say "target". What we're deprecating are hosts. (In a cross
compile setup the 'host' (machine being compiled for) isn't the
'build' (machine running the compiler), but I think if
you're advanced enough to be cross-compiling you can deal
with the confusing terminology.)

thanks
-- PMM