Update 20210914: Absoft support confirms that the behavior of af95
/ af90
described below is unintended and indeed a bug. Absoft developers will work to resolve it. The other compilers act correctly in this regard. Thank @Vladimir F for the answer, comments, and suggestions.
I have the impression that Fortran is cool with arrays of size 0. However, with Absoft Pro 21.0, I encountered a (strange) error involving such arrays. In contrast, gfortran
, ifort
, nagfor
, pgfortran
, sunf95
, and g95
are all happy with the same piece of code.
Below is a minimal working example.
! testempty.f90
!!!!!! A module that offends AF90/AF95 !!!!!!!!!!!!!!!!!!!!!!!!
module empty_mod
implicit none
private
public :: foo
contains
subroutine foo(n)
implicit none
integer, intent(in) :: n
integer :: a(0)
integer :: b(n - 1)
call bar(a) ! AF90/AF95 is happy with this line.
call bar(b) ! AF90/AF95 is angry with this line.
end subroutine foo
subroutine bar(x)
implicit none
integer, intent(out) :: x(:)
x = 1 ! BAR(B) annoys AF90/AF95 regardless of this line.
end subroutine bar
end module empty_mod
!!!!!! Module ends !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!! Main program !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
program testempty
use empty_mod, only : foo
implicit none
call foo(2) ! AF90/AF95 is happy with this line.
call foo(1) ! AF90/AF95 is angry with this line.
write (*, *) 'Succeed!' ! Declare victory when arriving here.
end program testempty
!!!!!! Main program ends !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Name this piece of code as testempty.f90
. Then run
$ af95 -no-pie -et -Rb -g -O0 -o atest testempty.f90
$ ./atest
This is what happened on my machine (Ubuntu 20.04, linux 5.4.0-77-generic, x86_64):
./atest
? FORTRAN Runtime Error:
? Subscript 1 is out of range for dimension 1 for array
? B with bounds 1:
? File testempty.f90; Line 19
? atest, run-time exception on Mon Sep 13 14:08:41 2021
? Program counter: 000000001004324B
? Signal SIGABRT, Abort
? Traceback follows
OBJECT PC ROUTINE LINE SOURCE
libpthread.so.0 000000001004324B raise N/A N/A
atest 00000000004141F3 __abs_f90rerr N/A N/A
atest 000000000041CA81 _BOUNDS_ERROR N/A N/A
atest 00000000004097B4 __FOO.in.EMPTY_MO N/A N/A
atest 000000000040993A MAIN__ 40 testempty.f90
atest 000000000042A209 main N/A N/A
libc.so.6 000000000FD0C0B3 __libc_start_main N/A N/A
atest 000000000040956E _start N/A N/A
So af95
was annoyed by call bar(b)
. With af90
, the result was the same.
I tested the same code using gfortran
, ifort
, nagfor
, pgfortran
, sunf95
, and g95
. All of them were quite happy with the code even though I imposed bound checking explicitly. Below is the Makefile
for the tests.
# This Makefile tests the following compilers on empty arrays.
#
# af95: Absoft 64-bit Pro Fortran 21.0.0
# gfortran: GNU Fortran (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
# ifort: ifort (IFORT) 2021.2.0 20210228
# nagfor: NAG Fortran Compiler Release 7.0(Yurakucho) Build 7036
# pgfortran: pgfortran (aka nvfortran) 21.3-0 LLVM 64-bit x86-64
# sunf95: Oracle Developer Studio 12.6
# g95: G95 (GCC 4.0.3 (g95 0.94!) Jan 17 2013)
#
# Tested on Ubuntu 20.04 with Linux 5.4.0-77-generic x86_64
.PHONY: test clean
test:
make -s gtest
make -s itest
make -s ntest
make -s ptest
make -s stest
make -s 9test
make -s atest
gtest: FC = gfortran -Wall -Wextra -fcheck=all
itest: FC = ifort -warn all -check all
ntest: FC = nagfor -C
ptest: FC = pgfortran -C -Mbounds
stest: FC = sunf95 -w3 -xcheck=%all -C
9test: FC = g95 -Wall -Wextra -fbounds-check
atest: FC = af95 -no-pie -et -Rb
%test: testempty.f90
$(FC) -g -O0 -o $@ $<
./$@
clean:
rm -f *.o *.mod *.dbg *test
Questions:
af95
/af90
standard-conforming?By "standards", I mean 2003, 2008, and 2018.
Thank you very much for any comments or criticism.
(The same question is posed on Fortran Discourse, and I hope it does not violate the rules here.)
The program looks OK to me. Zero-sized arrays are perfectly possible in Fortran although I admit I normally do not have automatic ones - but that is just a coincidence.
I think it is a compiler bug in the Absoft compiler or its array bounds checker.