https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79430
--- Comment #9 from Jürgen Reuter <juergen.reuter at desy dot de> --- (In reply to kargl from comment #7) > (In reply to Jürgen Reuter from comment #6) > > (In reply to Dominique d'Humieres from comment #5) > > > What does --with-precision=extended? > > > > It sets the default precision of real and complex floats (kind type > > parameter) to 80 bit instead of 64 bit (double) or 128bit (quadruple) > > precision according to: > > > > !!! available REAL kinds ! prec. ! ISO ! C > > integer, parameter :: single = 4 ! 1.. 6 ! real32 ! c_float > > integer, parameter :: double = 8 ! 7..15 ! real64 ! c_double > > integer, parameter :: extended = 10 ! 16..18 ! real128 ! c_long_double > > integer, parameter :: quadruple = 16 ! 19..33 ! -1 ! c_float128 > > > > integer, parameter :: default = extended > > Your use of terminology is unclear. The default real type in > Fortran is REAL. Real has a default real kind type value of 4. > This means that REAL == REAL(4), which is 32 bits. If you are > using some configure magic to map REAL to REAL(10), your version > of gfortran is too broken to save. > > Also note, I just fixed gfortran so that your table above is wrong. > If the four real types with kind = 4, 8, 10, and 16 are available. > Then the mapping is REAL(4) == REAL32, REAL(8) == REAL64, and > REAL(16) == REAL128. > > If a clever user messes up what default precision means, then > that clever user gets what they deserve. see my comment #8.
