[Bug fortran/54389] New: [F2003/F2008 difference] PURE functions and pointer dummy arguments
burnus at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Aug 28 08:10:00 GMT 2012
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54389
Bug #: 54389
Summary: [F2003/F2008 difference] PURE functions and pointer
dummy arguments
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Keywords: diagnostic, rejects-valid
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: burnus@gcc.gnu.org
Broad up in the comp.lang.fortran "Function questions?" thread
https://groups.google.com/forum/?fromgroups=#!topic/comp.lang.fortran/r4PVbtaBnFM
Ian Harvey remarks there that Fortran 2008 removed a restriction regarding
PURE.
Fortran 2003 has:
"C1272 In a pure subprogram any designator with a base object that [...] is a
dummy argument of a pure function, is a dummy argument with INTENT (IN) of a
pure subroutine [...] shall not be used in the following contexts: [...]"
Fortran 2008 changed it to:
"C1283 In a pure subprogram any designator with a base object that [...] is a
dummy argument with the INTENT (IN) attribute [...] shall not be used [...]"
Note: Both standards (F2003:C1266, F2008:C1276) require that all *nonpointer*
dummy arguments to pure *functions* have the INTENT(IN) or VALUE attribute.
However, there is no such restriction for pointers. Hence, an INTENT(OUT) or
INTENT(INOUT) pointer is allowed - also for functions - and it may be used in
pointer assignments (both sides), variable definition contexts etc. - like in a
normal procedure.
Currently, the following program is rejected with:
Error: Variable 'ptr' can not appear in a variable definition context
(assignment) at (1) in PURE procedure
(As a side remark: I wonder whether it should be made clearer that this applies
to a pure FUNCTION rather than to a pure SUBROUTINE. And the error message
feels a bit incomplete, maybe one should add the procedure name at the end.)
PURE INTEGER FUNCTION foo (ptr)
INTEGER, INTENT(INOUT), POINTER :: ptr
ptr = ptr + 1
foo = 1
END FUNCTION foo
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