On 2016-12-08 10:28:17 +0100, Mason wrote: > On 06/12/2016 12:39, Vincent Lefevre wrote: > > > So, in C, long double = x86 extended precision (80 bits + padding). > > That statement is incorrect. It is correct, but you should have taken the context into account (which I had quoted): "I faced strange problem with long double (C) in comparison with fortran (gfortran) on my system: Archlinux x86_64, gcc 6.2.1 20160830." So, what I said was for *this* system, and "in C" should have been read as "as opposition to Fortran" (not in C in general). Sorry if this wasn't clear. > More specifically, > [C99] 5.2.4.2.2 Characteristics of floating types <float.h> > > Smallest valid values for > > DBL_DIG = LDBL_DIG = 10 > DBL_MAX = LDBL_MAX = 1E+37 > DBL_EPSILON = LDBL_EPSILON = 1E-9 > > In other words, the C standard allows "long double" to be strictly > equivalent to "double". (I don't think that changed in C11.) Yes, and my message contained a link to the Wikipedia article on "long double", giving what one can find in practice on various platforms. -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
