https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86312
Bug ID: 86312
Summary: missing runtime warning for array temporary with
-fcheck=array-temps
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: janus at gcc dot gnu.org
Target Milestone: ---
Consider this test case:
program array_temp
type :: t
integer :: i = 3
real :: r = 0.
end type
integer, allocatable, dimension(:,:) :: ia
type(t), dimension(10) :: xx
allocate(ia(1:10,1:10), source=1)
call sub(ia(1,:)) ! runtime warning: array temporary
call sub(ia(:,1))
call sub(xx(:)%i) ! no runtime warning?!?
contains
subroutine sub(arg)
integer, dimension(:), contiguous :: arg
print *, arg
end subroutine
end
The flag -Warray-temporaries correctly warns for array temporaries at compile
time:
array_temp.f90:12:9:
call sub(ia(1,:)) ! runtime warning: array temporary
1
Warning: Creating array temporary at (1) for argument ‘arg’
[-Warray-temporaries]
array_temp.f90:15:9:
call sub(xx(:)%i) ! no runtime warning?!?
1
Warning: Creating array temporary at (1) [-Warray-temporaries]
However, -fcheck=array-temps only catches the first case, not the second one.
Related question: If the compile-time check catches all of this, why do we need
a runtime check at all? Are there cases that are only catchable at runtime, but
not at compile time?
Minor documentation issue: -Warray-temporaries is not listed on
https://gcc.gnu.org/onlinedocs/gfortran/Option-Summary.html, therefore I had a
hard time finding it. Also: Couldn't it be included in -Wall or at least
-Wextra?
