Le decadi 10 frimaire, an CCXXIV, Michael Niedermayer a écrit : > > ISO/IEC 9899:TC3 > > 5.2.4.2.2 Characteristics of floating types <float.h> > > > > 8 Except for assignment and cast (which remove all extra range and > > precision), the values > > of operations with floating operands and values subject to the usual > > arithmetic > > conversions and of floating constants are evaluated to a format whose > > range and precision > > may be greater than required by the type. The use of evaluation formats > > is characterized > > by the implementation-defined value of FLT_EVAL_METHOD:19) > > -1 indeterminable; > > 0 evaluate all operations and constants just to the range and > > precision of the > > type; > > 1 evaluate operations and constants of type float and double > > to the > > range and precision of the double type, evaluate long double > > operations and constants to the range and precision of the > > long double > > type; > > 2 evaluate all operations and constants to the range and > > precision of the > > long double type. > > All other negative values for FLT_EVAL_METHOD characterize > > implementation-defined > > behavior. > > a few more related parts: > 5 The accuracy of the floating-point operations (+, -, *, /) and of the > library functions in > <math.h> and <complex.h> that return floating-point results is > implementation- > defined, as is the accuracy of the conversion between floating-point > internal > representations and string representations performed by the library > functions in > <stdio.h>, <stdlib.h>, and <wchar.h>. The implementation may state that > the > accuracy is unknown. > > 6.4.4.2 Floating constants > 7 The translation-time conversion of floating constants should match the > execution-time > conversion of character strings by library functions, such as strtod, > given matching > inputs suitable for both conversions, the same result format, and default > execution-time > rounding.64)
I am not sure why you quoting this. Are you implying this is not a compiler bug, the compiler is actually allowed to do that? Possible. But still, I do not think we should apply this unless we actually understand what is going on here, why a cast that should not change anything does change the result. Otherwise, it could just be a coincidence, and break in a different way on a different compiler. Regards, -- Nicolas George
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