[Bug fortran/32083] New: bug in transfer integer->real->integer

["kloedej at knmi dot nl" <gcc-bugzilla@gcc.gnu.org>]

Hi,

It seems the current gfortran version has a bug when the transfer() function is
called on a parameter holding the bitpattern corresponding to the -Infinite
value.

If a variable with this pattern is transferred from integer->real->integer the
result is just the input. However, when a parameter is transferred in this way,
the sign gets reversed, and the bitpattern for -Infinite is changed into the
bit pattern for +Infinite.

I used the following sample code to test this:

PROGRAM TestInfinite

  IMPLICIT NONE
  integer, parameter :: i8_ = Selected_Int_Kind(18)  ! = integer*8
  integer, parameter :: r8_ = Selected_Real_Kind(15,307)  ! = real*8

  integer(i8_), parameter :: bit_pattern_PosInf_i8_p = 9218868437227405312_i8_
  integer(i8_), parameter :: bit_pattern_NegInf_i8_p = -4503599627370496_i8_

  integer(i8_) :: bit_pattern_PosInf_i8 = 9218868437227405312_i8_
  integer(i8_) :: bit_pattern_NegInf_i8 = -4503599627370496_i8_

  integer(i8_) :: bit_pattern_PosInf_i8_hex
  integer(i8_) :: bit_pattern_NegInf_i8_hex

  integer(i8_) :: i
  real(r8_)    :: r

  data bit_pattern_PosInf_i8_hex /z'7FF0000000000000'/
  !data bit_pattern_NegInf_i8_hex /z'FFF0000000000000'/
  ! not portable, replaced by:
  bit_pattern_NegInf_i8_hex = ibset(bit_pattern_PosInf_i8_hex,63)

  print *,"testing the values"

  print *,"bit_pattern_NegInf_i8_hex = ",bit_pattern_NegInf_i8_hex
  print *,"bit pattern NegInf_i8     = ",bit_pattern_NegInf_i8
  print *,"bit_pattern_PosInf_i8_hex = ",bit_pattern_PosInf_i8_hex
  print *,"bit pattern PosInf_i8     = ",bit_pattern_PosInf_i8

  print *,"testing the variable transfers"

  print *,"i = ",bit_pattern_PosInf_i8
  r = transfer(bit_pattern_PosInf_i8,r)
  print *,"r = ",r
  i = transfer(r,i)
  print *,"i = ",i

  print *,"i = ",bit_pattern_NegInf_i8
  r = transfer(bit_pattern_NegInf_i8,r)
  print *,"r = ",r
  i = transfer(r,i)
  print *,"i = ",i


  print *,"testing the parameter transfers"

  print *,"i = ",bit_pattern_PosInf_i8_p
  r = transfer(bit_pattern_PosInf_i8_p,r)
  print *,"r = ",r
  i = transfer(r,i)
  print *,"i = ",i

  print *,"i = ",bit_pattern_NegInf_i8_p
  r = transfer(bit_pattern_NegInf_i8_p,r)
  print *,"r = ",r
  i = transfer(r,i)
  print *,"i = ",i

END PROGRAM TestInfinite

This program generates the following output on my machine:

12:11pm bhw034 72 >TestInf
 testing the values
 bit_pattern_NegInf_i8_hex =     -4503599627370496
 bit pattern NegInf_i8     =     -4503599627370496
 bit_pattern_PosInf_i8_hex =   9218868437227405312
 bit pattern PosInf_i8     =   9218868437227405312
 testing the variable transfers
 i =   9218868437227405312
 r =                +Infinity
 i =   9218868437227405312
 i =     -4503599627370496
 r =                -Infinity
 i =     -4503599627370496
 testing the parameter transfers
 i =   9218868437227405312
 r =                +Infinity
 i =   9218868437227405312
 i =     -4503599627370496
 r =                +Infinity
 i =   9218868437227405312
12:11pm bhw034 73 >


The gfortran version used for testing was:
gfortran -v
Using built-in specs.
Target: i386-pc-linux-gnu
Configured with: /home/fxcoudert/gfortran_nightbuild/trunk/configure
--prefix=/home/fxcoudert/gfortran_nightbuild/irun-20070525
--enable-languages=c,fortran --build=i386-pc-linux-gnu
--enable-checking=release
--with-gmp=/home/fxcoudert/gfortran_nightbuild/software
Thread model: posix
gcc version 4.3.0 20070525 (experimental)



best regards,

Jos de Kloe


-- 
           Summary: bug in transfer integer->real->integer
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kloedej at knmi dot nl


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32083