Fortran code containing preprocessor instructions needed for handling
system-specific behaviour is traditionally written to files with
the extension .F (rather than .f). The GCC driver would preprocess this
file in a first step, writing the intermediate code to a temporary .f file.
The regression (observed with both GCC 4.0.1 (gfortran) and GCC 3.3.6 (g77))
is that the preprocessing stage fails (3.3.6) when any Fortran-specific options
are used (e.g. '-Wsurprising' as an option known to both gfortran and g77)
or issues a warning about an unrecognized option (4.0.1).
This worked in older versions (tested with 3.4.3, 3.3.3, 3.2, 3.0.4).
If the code in the .F file does not contain preprocessor instructions, one
could explicitly set the language ('-x f77') to force acceptance of the
Fortran specific options - but the preprocessor stage is skipped then
in all GCC versions, just as if using a .f file name extension.
To fix this regression, the preprocessing stage should accept (and ignore) the
Fortran-specific options, as it used to be in earlier versions.
Not sure if this should be assigned to the preprocessor or the driver component.
While 4.0.1 just issues an irritating warning and continues, no
Fortran-specific options can be used anymore for .F files to be preprocessed
in 3.3.6 (and perhaps 3.4.4, untested).
Demonstration script hello.sh (use as 'FC=g77 ./hello.sh' with GCC 3.x.x):
#!/bin/sh
if [ -z $FC ]; then
FC="gfortran"
fi
set -x
cat >hello.f <<EndOfF
Program MAIN
#ifdef TEST1
Write(*,*) 'Hello, world no. 1'
#else
Write(*,*) 'Hello, world no. 2'
#endif
End
EndOfF
ln -sf hello.f hello.F
echo "Without Fortran-specific option compilation works fine:"
${FC} -g -Wall -DTEST1 hello.F -o hello1
./hello1
${FC} -g -Wall hello.F -o hello2
./hello2
echo "Both gfortran and g77 version 3.3.6 (perhaps also 3.4.4?) fail/complain"
echo " with Fortran-specific options while older g77 version are OK:"
${FC} -g -Wall -Wsurprising hello.F -o hello
echo "When setting the language explicitly, the preprocessor is skipped:"
${FC} -g -Wall -Wsurprising -x f77 hello.F -o hello
--
Summary: [gfortran & g77] Regression compiling Fortran code with
preprocessor instructions
Product: gcc
Version: 4.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: driver
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: Konrad dot Bernloehr at mpi-hd dot mpg dot de
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i586-mandriva-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23532
