[Bug fortran/60128] [4.8/4.9 Regression] Wrong ouput using en edit descriptor

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60128

--- Comment #6 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
While preparing a test case, I have been hit by another snag!-(
With the trunk and 4.8, the following test

write(*,"(en15.2)") 98765.
write(*,"(en15.3)") 9876.5
write(*,"(en15.1)") 987.65
write(*,"(en15.2)") 98.765
write(*,"(en15.3)") 9.8765
write(*,"(en15.1)") .98765
write(*,"(en15.2)") .098765
write(*,"(en15.3)") .0098765
write(*,"(en15.1)") .00098765
write(*,"(en15.2)") .000098765
write(*,"(en15.2)") 98735.
write(*,"(en15.3)") 9873.5
write(*,"(en15.1)") 987.35
write(*,"(en15.2)") 98.735
write(*,"(en15.3)") 9.8735
write(*,"(en15.1)") .98735
write(*,"(en15.2)") .098735
write(*,"(en15.3)") .0098735
write(*,"(en15.1)") .00098735
write(*,"(en15.2)") .000098735
end

gives the following output at run time

      98.76E+03
      9.876E+03
      990.0E+00    <- wrong
      98.76E+00
      9.876E+00
      990.0E-03    <- wrong
      98.77E-03
      9.876E-03
      990.0E-06    <- wrong
      98.76E-06
      98.73E+03
      9.873E+03
      990.0E+00    <- wrong
      98.73E+00
      9.873E+00
      990.0E-03    <- wrong
      98.73E-03
      9.873E-03
      990.0E-06    <- wrong
      98.73E-06

while 4.7 gives

      98.77E+03
      9.877E+03
      987.7E+00
      98.76E+00
      9.877E+00
      987.6E-03
      98.77E-03
      9.876E-03
      987.7E-06
      98.76E-06
      98.74E+03
      9.874E+03
      987.3E+00
      98.74E+00
      9.873E+00
      987.3E-03
      98.73E-03
      9.874E-03
      987.4E-06
      98.73E-06

The reason of these wrong code is due to the rounding of x between 0.95*10**d
and 1.0*10**d to 1.*10**d. it follows that the exponent returned by 'nprinted =
DTOA(y,0,tmp);' in '#define EN_PREC(x,y)' is the actual exponent 'e' plus one.
I don't understand why this affects only the cases 'e%3==0' and I have no idea
how this can be fixed -> any help welcomed!.

Note that for the "working" cases I am not fully happy with the rounding: at
least for 98765., 9876.5, 98735., and 9873.5 which have no rounding errors, I
am expecting with round to even on tie: 98.76E+03, 98.76E+03, 98.74E+03, and
98.74E+03.