[gcc r12-10148] Fortran: fix bounds-checking errors for CLASS array dummies [PR104908]

[Harald Anlauf]

https://gcc.gnu.org/g:f7b3a82be2f4e9f43524185226c0df686c7b0154

commit r12-10148-gf7b3a82be2f4e9f43524185226c0df686c7b0154
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Sat Jan 27 17:41:43 2024 +0100

    Fortran: fix bounds-checking errors for CLASS array dummies [PR104908]
    
    Commit r11-1235 addressed issues with bounds of unlimited polymorphic array
    dummies.  However, using the descriptor from sym->backend_decl does break
    the case of CLASS array dummies.  The obvious solution is to restrict the
    fix to the unlimited polymorphic case, thus keeping the original descriptor
    in the ordinary case.
    
    gcc/fortran/ChangeLog:
    
            PR fortran/104908
            * trans-array.cc (gfc_conv_array_ref): Restrict use of transformed
            descriptor (sym->backend_decl) to the unlimited polymorphic case.
    
    gcc/testsuite/ChangeLog:
    
            PR fortran/104908
            * gfortran.dg/pr104908.f90: New test.
    
    (cherry picked from commit ce61de1b8a1bb3a22118e900376f380768f2ba59)

Diff:
---
 gcc/fortran/trans-array.cc             |  5 ++++-
 gcc/testsuite/gfortran.dg/pr104908.f90 | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index f7097ee41651..c82b1fa47e59 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -3911,7 +3911,10 @@ gfc_conv_array_ref (gfc_se * se, gfc_array_ref * ar, gfc_expr *expr,
     }
 
   decl = se->expr;
-  if (IS_CLASS_ARRAY (sym) && sym->attr.dummy && ar->as->type != AS_DEFERRED)
+  if (UNLIMITED_POLY(sym)
+      && IS_CLASS_ARRAY (sym)
+      && sym->attr.dummy
+      && ar->as->type != AS_DEFERRED)
     decl = sym->backend_decl;
 
   cst_offset = offset = gfc_index_zero_node;
diff --git a/gcc/testsuite/gfortran.dg/pr104908.f90 b/gcc/testsuite/gfortran.dg/pr104908.f90
new file mode 100644
index 000000000000..c3a30b0003c5
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr104908.f90
@@ -0,0 +1,32 @@
+! { dg-do compile }
+! { dg-additional-options "-fcheck=bounds -fdump-tree-original" }
+!
+! PR fortran/104908 - incorrect out-of-bounds runtime error
+
+program test
+  implicit none
+  type vec
+     integer :: x(3) = [2,4,6]
+  end type vec
+  type(vec) :: w(2)
+  call sub(w)
+contains
+  subroutine sub (v)
+    class(vec), intent(in) :: v(:)
+    integer :: k, q(3)
+    q = [ (v(1)%x(k), k = 1, 3) ]   ! <-- was failing here after r11-1235
+    print *, q
+  end
+end
+
+subroutine sub2 (zz)
+  implicit none
+  type vec
+     integer :: x(2,1)
+  end type vec
+  class(vec), intent(in) :: zz(:)   ! used to ICE after r11-1235
+  integer :: k
+  k = zz(1)%x(2,1)
+end
+
+! { dg-final { scan-tree-dump-times " above upper bound " 4 "original" } }