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
