Hi Paul!
On 4/10/24 10:25, Paul Richard Thomas wrote:
Hi All,
This patch corrects incorrect results from assignment of unlimited
polymorphic function results both in assignment statements and allocation
with source.
The first chunk in trans-array.cc ensures that the array dtype is set to
the source dtype. The second chunk ensures that the lhs _len field does not
default to zero and so is specific to dynamic types of character.
The addition to trans-stmt.cc transforms the source expression, aka expr3,
from a derived type of type "STAR" into a proper unlimited polymorphic
expression ready for assignment to the newly allocated entity.
I am wondering about the following snippet in trans-stmt.cc:
+ /* Copy over the lhs _data component ref followed by the
+ full array reference for source expressions with rank.
+ Otherwise, just copy the _data component ref. */
+ if (code->expr3->rank
+ && ref && ref->next && !ref->next->next)
+ {
+ rhs->ref = gfc_copy_ref (ref);
+ rhs->ref->next = gfc_copy_ref (ref->next);
+ break;
+ }
Why the two gfc_copy_ref? valgrind pointed my to the tail
of gfc_copy_ref which already has:
dest->next = gfc_copy_ref (src->next);
so this looks redundant and leaks frontend memory?
***
Playing with the testcase, I find several invalid writes with
valgrind, or a heap buffer overflow with -fsanitize=address .
It is sufficient to look at a mini-test where the class(*) function
result is assigned to the class(*), allocatable in the main:
x = foo ()
deallocate (x)
The dump tree suggests that array bounds in foo() are read before
they are properly set.
These invalid writes do not occur with 13-branch, so this might
be a regression.
Can you have a look yourself?
Thanks,
Harald
OK for mainline?
Paul
Fortran: Fix wrong code in unlimited polymorphic assignment [PR113363]
2024-04-10 Paul Thomas <pa...@gcc.gnu.org>
gcc/fortran
PR fortran/113363
* trans-array.cc (gfc_array_init_size): Use the expr3 dtype so
that the correct element size is used.
(gfc_alloc_allocatable_for_assignment): Set the _len field for
unlimited polymorphic assignments.
* trans-stmt.cc (gfc_trans_allocate): Build a correct rhs for
the assignment of an unlimited polymorphic 'source'.
gcc/testsuite/
PR fortran/113363
* gfortran.dg/pr113363.f90: New test.
