Re: powerpc-g++ 4.2.4 problem casting long long to double

[Koen Kooi <k.kooi@student.utwente.nl>]

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On 19-05-10 17:46, Vitus Jensen wrote:
> On Wed, 19 May 2010, Vitus Jensen wrote:
>> On Wed, 19 May 2010, Gary Thomas wrote:
>>>  On 05/19/2010 03:38 AM, Vitus Jensen wrote:
>>> > >   We noticed a strange problem with C++ code casting long long
>>> variables
>>> >   to double, as a lot of qt-embedded code is doing.
>>> > >   =================
>>> >   double
>>> >   convert(long long l)
>>> >   {
>>> >   return (double)l; // or double(l)
>>> >   }
>>> > >   int
>>> >   main(int argc, char * argv[])
>>> >   {
>>> >   long long l = 10;
>>> >   double f;
>>> > >   f = convert(l);
>>> >   printf("convert: %lld => %f\n", l, f);
>>> >   return 0;
>>> >   }
>>> >   ====================
>>> > >   output:
>>> >   convert: 10 => 0.000000
>>> > >   C++ compiled via powerpc-angstrom-linux-g++ gives the above
>>> result.
>>> >   Compiling the same code as C using powerpc-angstrom-linux-gcc works
>>> >   fine. But when looking at the assembler code both compiler produce
>>> >   virtually identical output and both call __floatdidf to do the
>>> actual
>>> >   conversion. Very strange, has anyone ever seen similar effects?
>>>
>>>  Is this from a recent tree (i.e. post Richard Purdie's restructuring)?
>>>
>>>  I've seen similar problems with C++ code on Poky which uses the same
>>>  changes.
>>
>> No, I'm building everything from the stable branch.  There were some
>> commits cherry-picked from .dev but those only add Qt 4.5.2.
>>
>> Poky is ARM only, right?  Perhaps it would be helpfull to build a
>> compiler from .dev and for a widely used powerpc-platform?  How does
>> n1200 sound? It uses the same ppc603e.
> 
> Unfortunately .dev switched to gcc-4.3.3 in the meantime which fails for
> ppc603e platforms because of undefined references to __nldbl_fprintf and
> __nldbl_sprintf during compile.
> 
> Platform tqm8540 (ppce500, just to try some other ppc cpu) fails in
> gcc-4.3.3 compile, too.  Possible related to this:
> 
> endian.h:34:4: warning: #warning Cannot determine current byte order,
> assuming big-endian.
> 
> So currently .dev should be unbuildable for ppc users?  Without
> selecting a non-default compiler that is.

I thought I pinned powerpc at 4.1.1, but it turns out that it was only
for ppc405:

ANGSTROM_GCC_VERSION_ppc405         ?= "4.1.1"

Feel free to send patches to add that for other ppc platforms.

regards,

Koen
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