https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97592
Bug ID: 97592
Summary: Incorrectly set pointer remapping with array pointer
argument to CONTIGUOUS dummy
Product: gcc
Version: og10 (devel/omp/gcc-10)
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: reubendb at gmail dot com
Target Milestone: ---
Hi,
The following code produces an incorrect results with GCC 10.1.0, 10.2.0.
The code works as expected with GCC/6.4.0,7.4.0,8.1.0,8.1.1
program RemappingTest
implicit none
real, dimension ( :, : ), pointer :: &
B_2D
real, dimension ( :, :, : ), pointer :: &
B_3D
!-- Prepare B_2D
allocate ( B_2D ( 16, 3 ) )
B_2D = - huge ( 1.0 )
!-- Point B_3D to Storage
call SetPointer ( B_2D, 4, 4, 3, B_3D )
!-- Set B_3D
B_3D = 2.0
!-- See if the result is reflected in Storage
print*
print*, "B_2D = ", B_2D !-- expect 2.0 for all elements
contains
subroutine SetPointer ( C_2D, n1, n2, n3, C_3D )
real, dimension ( :, : ), intent ( inout ), target, contiguous :: &
C_2D
integer :: &
n1, n2, n3
real, dimension ( :, :, : ), intent ( inout ), pointer :: &
C_3D
C_3D ( 1 : n1, 1 : n2, 1 : n3 ) => C_2D
end subroutine SetPointer
end program RemappingTest
]$ gfortran --version
GNU Fortran (GCC) 10.2.0
Copyright (C) 2020 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.
]$ gfortran -Wall -Wextra -fno-strict-aliasing -fwrapv -Warray-temporaries
PointerRemapTest.f90
PointerRemapTest.f90:13:20:
13 | call SetPointer ( B_2D, 4, 4, 3, B_3D )
| 1
Warning: Creating array temporary at (1) [-Warray-temporaries]
]$ ./a.out
B_2D = -3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
-3.40282347E+38 -3.40282347E+38 -3.40282347E+38 -3.40282347E+38
It seems to be issue is because inside the subroutine SetPointer, a new array
`C_2D` is created. So `C_3D` points to this new array instead. Outside of
subroutine, this pointer (now `B_3D`) actually points to an invalid memory
location. In some cases I can trigger a segfault with the code with GCC-10.2.0
