https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112459
Bug ID: 112459
Summary: gfortran -w option causes derived-type finalization at
creation time
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: bardeau at iram dot fr
Target Milestone: ---
Hi everyone,
with gfortran version 13.2.0, the -w compilation switch modifies the code
behavior at execution time. This was not the case with e.g. gfortran 12.1.0.
~> gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/home/bardeau/Softs/gcc-13.2.0/libexec/gcc/x86_64-pc-linux-gnu/13.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../srcdir/configure --with-gmp=/home/bardeau/Softs/gcc-deps
--prefix=/home/bardeau/Softs/gcc-13.2.0 --enable-languages=c,c++,fortran
--disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.2.0 (GCC)
Code example:
module mymod
type mysubtype
integer(kind=4), allocatable :: a(:)
end type mysubtype
type :: mytype
integer :: i
type(mysubtype) :: sub
contains
final :: mytype_final
end type mytype
contains
subroutine mysubtype_final(sub)
type(mysubtype), intent(inout) :: sub
print *,'MYSUBTYPE>FINAL'
if (allocated(sub%a)) deallocate(sub%a)
end subroutine mysubtype_final
subroutine mytype_final(typ)
type(mytype), intent(inout) :: typ
print *,"MYTYPE>FINAL"
call mysubtype_final(typ%sub)
end subroutine mytype_final
end module mymod
!
program myprog
use mymod
type(mytype), pointer :: c
print *,"Before allocation"
allocate(c)
print *,"After allocation"
end program myprog
Compilation and execution:
~> gfortran -w test1.f90 -o test1 && ./test1
Before allocation
MYTYPE>FINAL
MYSUBTYPE>FINAL
After allocation
The problem is that the FINAL procedure (mytype_final) is invoked at the time
the c variable is allocated, which is unexpected. Plus, this behavior is
random. If the "sub" component is removed from "mytype", mytype_final is not
invoked anymore. I also have a much more complex example where the program
crashes because the evaluation "allocated(sub%a)" is incorrect and leads to
deallocation of the unallocated "sub%a". All these behaviors are correlated to
the presence of the -w option.
In order to be complete, I must say that the -w option is not described in
https://gcc.gnu.org/onlinedocs/gcc-13.2.0/gfortran/Error-and-Warning-Options.html
but it is suggested in -fallow-argument-mismatch (documented here:
https://gcc.gnu.org/onlinedocs/gcc-13.2.0/gfortran/Fortran-Dialect-Options.html
). In practice it can be used for example with:
subroutine test
call foo()
call foo(1)
end subroutine test
~> gfortran -c -fallow-argument-mismatch -w test2.f90
which shows no warning thanks to -w.
