https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83745
Bug ID: 83745
Summary: Errors using the max intrinsic in a PDT length
parameter expression for a function result
Product: gcc
Version: 8.0
Status: RESOLVED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: berke.durak at gmail dot com
Target Milestone: ---
Status: RESOLVED
Resolution: DUPLICATE
Found another one. When a length parameter for a function
result is dynamically computed from argument parameters,
the max() intrinsic causes spurious warnings and the parameter
is set incorrectly, possibly uninitialized at run time:
module pdt_m
implicit none
type :: vec(k)
integer, len :: k=0
integer :: foo(k)
end type vec
contains
elemental function diy_max(a,b) result(c)
integer, intent(in) :: a,b
integer :: c
c=max(a,b)
end function diy_max
function add(a,b) result(c)
type(vec(k=*)), intent(in) :: a,b
type(vec(k=max(a%k,b%k))) :: c ! Fails
!type(vec(k=diy_max(a%k,b%k))) :: c ! Works with diy_max
!type(vec(k=a%k+b%k)) :: c ! Works with +
c%foo=0
c%foo(1:a%k)=a%foo
c%foo(1:b%k)=c%foo(1:b%k)+b%foo
print *,'c%k=',c%k
end function add
end module pdt_m
program test_pdt
use pdt_m
implicit none
type(vec(k=2)) :: u
type(vec(k=3)) :: v,w
print *,'w%k=',w%k
print *,'size(w%foo)=',size(w%foo)
u%foo=[1,2]
v%foo=[10,20,30]
w=add(u,v)
print *,'w%k=',w%k
print *,'size(w%foo)=',size(w%foo)
end program test_pdt
% /usr/local/gfortran-bin/bin/gfortran pdt.f90 -o pdt -Wall -Wextra -g
pdt.f90:25:0:
end function add
Warning: ‘M.4’ is used uninitialized in this function [-Wuninitialized]
pdt.f90:25:0:
end function add
note: ‘M.4’ was declared here
pdt.f90:25:0:
end function add
Warning: ‘M.5’ is used uninitialized in this function [-Wuninitialized]
pdt.f90:25:0:
end function add
note: ‘M.5’ was declared here
% ./pdt
w%k= 3
size(w%foo)= 3
c%k= 329917520
w%k= 329917520
size(w%foo)= 0
And with -fcheck=all:
w%k= 3
size(w%foo)= 3
At line 21 of file pdt.f90
Fortran runtime error: Index '1' of dimension 1 of array 'c' outside of
expected range (1:0)
Error termination. Backtrace:
#0 0x400ded in __pdt_m_MOD_add
at /home/alpha/src/fortran/23_Parametrized_derived_types/pdt.f90:21
#1 0x40183d in test_pdt
at /home/alpha/src/fortran/23_Parametrized_derived_types/pdt.f90:39
#2 0x401a61 in main
at /home/alpha/src/fortran/23_Parametrized_derived_types/pdt.f90:29
Version:
% /usr/local/gfortran-bin/bin/gfortran --version
GNU Fortran (GCC) 8.0.0 20180109 (experimental) [trunk revision 256361]
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Dup.
*** This bug has been marked as a duplicate of bug 83746 ***
