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From: "john.harper at vuw dot ac.nz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/57871] New: gfortran -freal-4-real-16 gives wrong result for selected_real_kind(1)
Date: Tue, 09 Jul 2013 23:38:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57871

            Bug ID: 57871
           Summary: gfortran -freal-4-real-16 gives wrong result for
                    selected_real_kind(1)
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: john.harper at vuw dot ac.nz

gfortran 4.8.1 -freal-4-real-16 gives real(16) kind with selected_real_kind(1)
but it ought to give real(8) because that is the smallest decimal precision
available with that compiler option. Same problem with -freal-4-real-10 giving
real(10) instead of real(8). Evidence:

cayley[~/Jfh] % cat testprecision.f90
implicit none
integer,parameter:: p1 = selected_real_kind(1), dp = kind(1d0)
print *,'kind(1.0_p1)',kind(1.0_p1),'precision(1.0_p1)',precision(1.0_p1)
print *,'kind(1.0_dp)',kind(1.0_dp),'precision(1.0_dp)',precision(1.0_dp)
end
cayley[~/Jfh] % /local/scratch/gf/bin/gfortran -freal-4-real-16 -Wall -Wextra
-fno-strict-aliasing -fwrapv testprecision.f90
cayley[~/Jfh] % ./a.out
 kind(1.0_p1)          16 precision(1.0_p1)          33
 kind(1.0_dp)           8 precision(1.0_dp)          15
cayley[~/Jfh] % /local/scratch/gf/bin/gfortran -freal-4-real-10 -Wall -Wextra
-fno-strict-aliasing -fwrapv testprecision.f90
cayley[~/Jfh] % ./a.out                                                         
 kind(1.0_p1)          10 precision(1.0_p1)          18
 kind(1.0_dp)           8 precision(1.0_dp)          15
cayley[~/Jfh] % /local/scratch/gf/bin/gfortran -v
Using built-in specs.
COLLECT_GCC=/local/scratch/gf/bin/gfortran
COLLECT_LTO_WRAPPER=/local/scratch/gf/libexec/gcc/x86_64-unknown-linux-gnu/4.8.1/lto-wrapper
Target: x86_64-unknown-linux-gnu                                                
Configured with: /local/scratch/gcc-4.8-20130530/configure
--prefix=/local/scratch/gf --enable-languages=c,fortran --disable-libada
--with-local-prefix=/local/scratch --with-gmp=/local/scratch                    
Thread model: posix                                                             
gcc version 4.8.1 20130530 (prerelease) (GCC)                                   
cayley[~/Jfh] %