This is my first report at gcc Bugzilla...
I tried to compile a fortran program that invokes QD library (multiprecision
arithmetic, available at
http://www.cs.berkeley.edu/~yozo/software/qd-2.3.7.tar.gz). When I use Intel
compiler suite, everything is fine. If I switch to gcc (the performance of QD
is much better when it is compiled with g++ rather than Intel C++) then I get
the following error message:
In file f_main.f90:17
call random_number(s)
1
Error: There is no specific subroutine for the generic 'random_number' at (1)
make: *** [f_main.o] Error 1
I have investigated the issue a little it and came to the conclusion that there
is something wrong with interfacing in gfortran. The QD library has fortran
modules called ddmod.f90 and qdmod.f90 which contain the following:
interface random_number
module procedure ddrand
end interface
interface random_number
module procedure qdrand
end interface
random_number is interfaced to allow it to be called with the types or real
numbers implemented in QD [type(qd_real) and type(dd_real)]. But in my code I
want to call random_number with standard real(8) type. Intel fortran has no
problems with it, the compilation goes fine and the program runs as expected.
So there must be a bug in gfortran.
In order to make things work I simply removed those interfaces from qdmod.f90
and ddmod.f90 (I don't need random_number with type(qd_real) and type(dd_real)
anyway). After doing that everything goes fine.
--
Summary: A bug with interface in gfortran
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bubin at qcri dot or dot jp
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39253
