[cfe-dev] Complex values handling in Clang

[Hal Finkel]

----- Original Message -----
> From: "Stephen Canon" <scanon at apple.com>
> To: "rajesh viswabramana" <viswabramana.rajesh at gmail.com>
> Cc: cfe-dev at cs.uiuc.edu
> Sent: Friday, February 1, 2013 9:32:00 AM
> Subject: Re: [cfe-dev] Complex values handling in Clang
> 
> _Complex integer types are a GCC extension (the standard specifies
> only float _Complex, double _Complex and long double _Complex.
>  Apparently clang's support for this GCC extension doesn't perfectly
> match GCC.  I suspect that clang and GCC differ in arithmetic
> promotion rank here; clang "promotes" the unsigned long long
> literals to int _Complex (which truncates them), whereas GCC
> promotes both to unsigned long long _Complex.  I haven't actually
> dug into the issue at all, however.

Did Bill just fix this in r174181?

 -Hal

> 
> A couple of work-arounds seem to be available:
> 
> 	unsigned long long int _Complex lli_val = (unsigned long long int
> 	_Complex){5668231682443686620ULL, 7618395480654047911ULL};
> 
> 	unsigned long long int _Complex lli_val;
> 	__real__ lli_val = 5668231682443686620ULL;
> 	__imag__ lli_val = 7618395480654047911ULL;
> 
> I believe that both of these will work with recent GCCs as well.
> 
> - Steve
> 
> On Feb 1, 2013, at 12:06 AM, rajesh viswabramana
> <viswabramana.rajesh at gmail.com> wrote:
> 
> > Hi all,
> >  
> > Could someone comment about it.
> >  
> > Thanks,
> > Rajesh
> > 
> > On Mon, Jan 28, 2013 at 7:16 PM, rajesh viswabramana
> > <viswabramana.rajesh at gmail.com> wrote:
> > Hi All,
> > 
> > Complex values stored in variable value mismatches if program
> > compiled clang and gcc.
> >  
> > Below is the sample program printing byte by byte stored "complex
> > long long int" value,
> > int main()
> > {
> >  _Complex unsigned long long int lli_val= (5668231682443686620ULL +
> >  7618395480654047911ULL*__extension__ 1i);
> > // _Complex long double ld_val = (5668231682443686620ULL +
> > 7618395480654047911ULL*__extension__ 1i);
> >  int size = sizeof(lli_val);
> >  int index = 0;
> >  printf("long long int val:\n");
> >  while (size != index)
> >  {
> >     unsigned char cval = (unsigned char)*(((unsigned
> >     char*)&lli_val) + index);
> >     printf("%x", cval);
> >     index++;
> >  }
> > }
> > Outputs of clang compiled, gcc compiled values are:
> > For Clang,
> > long long int val:
> > dcb2ab00000a76ad35e0000
> > For GCC,
> > long long int val:
> > dcb2ab0af9aa94ea76ad35e53fab969
> > Similar behaviour observed for "_Complex float, _Complex double,
> > _Complex long double" types.
> > 
> > Complex values in clang are not handled in similar to GCC, Could
> > someone comment about it.
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>