Re: [Mingw-cross-env-list] Qt 4.7 (help wanted)

[Volker Grabsch]

Mark Brand <address@hidden> schrieb:
>> #include "..." search starts here:
>> #include<...>  search starts here:
>>   /Users/tonytheodore/dev/mingw-cross-env/usr/i686-pc-mingw32/include
>>   
>> /Users/tonytheodore/dev/mingw-cross-env/usr/lib/gcc/i686-pc-mingw32/4.5.0/include
>>   
>> /Users/tonytheodore/dev/mingw-cross-env/usr/lib/gcc/i686-pc-mingw32/4.5.0/include-fixed
>> End of search list.
>>
>> I've attached the modified spec file I used, the most important option
>> is -nostdinc. The only section I changed is the *cpp. I'd didn't get
>> to figuring out how to generate the file and putting it in the right
>> spot to be found automatically.
>
> That look like a good way to do that, if that's really what should be  
> done. What about my doubts about whether reordering the search path is  
> the correct approach?

Indeed, this might be the wrong approach. The "#include_next" stuff
is designed to be used by the _GCC_ headers in

    usr/lib/gcc/i686-pc-mingw32/4.5.0/include/

and _not_ by the _MinGW-runtime_ headers in

    usr/i686-pc-mingw32/include/

So the <float.h> of the MinGW-runtime took simply the wrong approach.


1) Clean Solution
=================

I think the only "clean" solution is to

    * remove the "#include_next" from MinGW-runtime's <float.h>:

            usr/i686-pc-mingw32/include/float.h

    * add a conditional "#include_next" to GCC's <float.h>:

            usr/lib/gcc/i686-pc-mingw32/4.5.0/include/float.h

      (similar to the "#include_next" mechanism of GCC's <stdint.h>:
       usr/lib/gcc/i686-pc-mingw32/4.5.0/include/stdint.h)

However, this solution requires changes to GCC as well as MinGW-runtime,
so whoever wants to solve it should discuss that with both groups.
I certainly don't have the time for that, but maybe someone else does?


2) Workaround
=============

In the meantime, I think the best approach is _not_ to try to "fix"
that, as any other "solution" won't be real solution to the underlying
problem. Even worse, such a hack might be mistaken for a proper solution,
leading others (like us :-)) to think that e.g. modifying the system
include paths is the way to go.

Instead, we should provide an explicit workaround until the problem
is really fixed. A workaround should be explicit and non-intrusive.
So I think it should only affect float.h under Qt, and nothing else.

My favourite approach, if it works, would be:

    * copy MinGW-runtime's <float.h> to Qt's include/ folder, i.e.:

            usr/i686-pc-mingw32/include/float.h
            ->
            tmp-qt/.../.../include/

            ./configure ...
            $(MAKE) ...

Do you think this is feasible?


Greets,
Volker

-- 
Volker Grabsch
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Administrator
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