https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78290
Bug ID: 78290
Summary: Gfortran incorrectly creates a copy of an array passed
to an array pointer dummy argument
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: andybugreports at gmail dot com
Target Milestone: ---
The following code demonstrates incorrect behaviour of a array pointer being
passed to an array pointer dummy argument. As highlighted in the comment, the
compiler seems to generate a copy of the array rather than passing a pointer to
it. "sub1" seems to be doing the right thing, but due to the copy and what
looks like incorrect behaviour to attempt to copy some of it back the result is
wrong. Removing the line shown later in the source stops the copy occurring and
fixes the problem. Bug 53800 looks potentially similar:
PROGRAM main
IMPLICIT NONE
INTEGER,PARAMETER::KI=4,KF=8,KL=4
TYPE mytype
INTEGER(KIND=KI)::i=1_KI
REAL(KIND=KF)::r=2.0_KF
LOGICAL(KIND=KL)::z=.TRUE._KL
END TYPE mytype
TYPE(mytype),DIMENSION(50),SAVE,TARGET::ta
INTEGER(KIND=KI),DIMENSION(3),SAVE,TARGET::ia=1_KI
INTEGER(KIND=KI),DIMENSION(:),POINTER::ia2=>NULL()
INTEGER(KIND=KI),DIMENSION(:),POINTER,SAVE::ipsave=>NULL()
INTEGER(KIND=KI),DIMENSION(:),POINTER::ip=>NULL()
ALLOCATE(ia2(5)); ia2=2_KI
ip=>ia; NULLIFY(ipsave)
CALL sub1(ip)
WRITE(*,*)'ia ',ia
WRITE(*,*)'ip ',ip
WRITE(*,*)'ipsave',ipsave
ip=>ta%i !!! Works if you comment this line out !!!
! At writes: isave should point to ia which should be changed to all 3s
! ip should point to ip2
! Produces:
! ia 2 2 2
! ip 2 2 2
! ipsave 3 3 3
!
! Should produce:
! ia 3 3 3
! ip 2 2 2 2 2
! ipsave 3 3 3
!
! Seems to be creating a copy of ia and setting argument ipa as a pointer this,
and
! changes to this never get transferred back to ia
! Also does not transfer back change of target or INOUT argugment
! Works if you comment out the line "ip=>ta%i"
!
CONTAINS
SUBROUTINE sub1(ipa)
INTEGER(KIND=KI),DIMENSION(:),POINTER,INTENT(INOUT)::ipa ! Fortran 2003
! INTEGER(KIND=KI),DIMENSION(:),POINTER::ipa ! Fortan 95
ipsave=>ipa
ipsave=3_KI
ipa=>ia2
END SUBROUTINE sub1
END PROGRAM main
