dereferencing type-punned pointer will break strict-aliasing rules

[Marcel Behlau <marcel.behlau@xxxxxxxx>]

Hi,

i wan't to create aliase (symbolic name and explizit type) for the 
elements of an char-array. Unfortunately my gcc produce the warning 
"dereferencing type-punned pointer will break strict-aliasing rules", if 
i use -O2 or bigger. Since i set -Werror, the warning will become an error.

I attached an example to this mail. To compile and generate the problem, 
i use "gcc -O2 -Werror -Wall main.cpp".

I found an workaround (without using pragma, or somethink else), with 
it's included in the code, too. To activate, pass an extra "-DWorking" 
to the gcc-Command. The workaround is working, but using an pointer is ugly.

Best regrads,

Marcel

--
Dipl. Ing (FH) Marcel Behlau
(Software Developer)

ELFIN GmbH
Siegburger Straße 215
50679 Köln
Germany

Tel: +49 (221) 6778932-0
Fax: +49 (221) 6778932-2
marcel.behlau@xxxxxxxx
www.elfin.de


//gcc -O2 -Wall main.cpp
//gcc -O2 -Wall main.cpp -DWorking

//#define Working

struct Ec
{
  char ecData;
};

class ClassZero
{
public:
  char data[8];
  char* pointer;
  Ec& ec0;

#ifdef Working
  ClassZero() : pointer(data), ec0(*(Ec*)(pointer)) { }
#else
  ClassZero() : ec0(*(Ec*)(data)) { }
#endif

};

int main()
{
    return 0;
}