Fortran: fix reallocation on assignment of polymorphic variables [PR110415]

This patch fixes two bugs related to polymorphic class assignment in the
Fortran front-end. One (described in PR110415) is an issue with the malloc
and realloc calls using the size from the old vptr rather than the new one.
The other is caused by the return value from the realloc call being ignored.
Testcases are added for these issues.

2023-11-28  Andrew Jenner  <andrew@codesourcery.com>

gcc/fortran/
	PR fortran/110415
	* trans-expr.cc (trans_class_vptr_len_assignment): Add
	from_vptrp parameter. Populate it. Don't check for DECL_P
	when deciding whether to create temporary.
	(trans_class_pointer_fcn, gfc_trans_pointer_assignment): Add
	NULL argument to trans_class_vptr_len_assignment calls.
	(trans_class_assignment): Get rhs_vptr from
	trans_class_vptr_len_assignment and use it for determining size
	for allocation/reallocation. Use return value from realloc.

gcc/testsuite/
	PR fortran/110415
	* gfortran.dg/pr110415.f90: New test.
	* gfortran.dg/asan/pr110415-2.f90: New test.
	* gfortran.dg/asan/pr110415-3.f90: New test.

Co-Authored-By: Tobias Burnus  <tobias@codesourcery.com>

4 files changed, 139 insertions, 14 deletions

diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 50c4604..bfe9996 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -9936,7 +9936,8 @@ trans_get_upoly_len (stmtblock_t *block, gfc_expr *expr)
 static tree
 trans_class_vptr_len_assignment (stmtblock_t *block, gfc_expr * le,
 				 gfc_expr * re, gfc_se *rse,
-				 tree * to_lenp, tree * from_lenp)
+				 tree * to_lenp, tree * from_lenp,
+				 tree * from_vptrp)
 {
   gfc_se se;
   gfc_expr * vptr_expr;
@@ -9944,10 +9945,11 @@ trans_class_vptr_len_assignment (stmtblock_t *block, gfc_expr * le,
   bool set_vptr = false, temp_rhs = false;
   stmtblock_t *pre = block;
   tree class_expr = NULL_TREE;
+  tree from_vptr = NULL_TREE;
 
   /* Create a temporary for complicated expressions.  */
   if (re->expr_type != EXPR_VARIABLE && re->expr_type != EXPR_NULL
-      && rse->expr != NULL_TREE && !DECL_P (rse->expr))
+      && rse->expr != NULL_TREE)
     {
       if (re->ts.type == BT_CLASS && !GFC_CLASS_TYPE_P (TREE_TYPE (rse->expr)))
 	class_expr = gfc_get_class_from_expr (rse->expr);
@@ -10044,6 +10046,7 @@ trans_class_vptr_len_assignment (stmtblock_t *block, gfc_expr * le,
 		tmp = rse->expr;
 
 	      se.expr = gfc_class_vptr_get (tmp);
+	      from_vptr = se.expr;
 	      if (UNLIMITED_POLY (re))
 		from_len = gfc_class_len_get (tmp);
 
@@ -10065,6 +10068,7 @@ trans_class_vptr_len_assignment (stmtblock_t *block, gfc_expr * le,
 	  gfc_free_expr (vptr_expr);
 	  gfc_add_block_to_block (block, &se.pre);
 	  gcc_assert (se.post.head == NULL_TREE);
+	  from_vptr = se.expr;
 	}
       gfc_add_modify (pre, lhs_vptr, fold_convert (TREE_TYPE (lhs_vptr),
 						se.expr));
@@ -10093,11 +10097,13 @@ trans_class_vptr_len_assignment (stmtblock_t *block, gfc_expr * le,
 	}
     }
 
-  /* Return the _len trees only, when requested.  */
+  /* Return the _len and _vptr trees only, when requested.  */
   if (to_lenp)
     *to_lenp = to_len;
   if (from_lenp)
     *from_lenp = from_len;
+  if (from_vptrp)
+    *from_vptrp = from_vptr;
   return lhs_vptr;
 }
 
@@ -10166,7 +10172,7 @@ trans_class_pointer_fcn (stmtblock_t *block, gfc_se *lse, gfc_se *rse,
     {
       expr1_vptr = trans_class_vptr_len_assignment (block, expr1,
 						    expr2, rse,
-						    NULL, NULL);
+						    NULL, NULL, NULL);
       gfc_add_block_to_block (block, &rse->pre);
       tmp = gfc_create_var (TREE_TYPE (rse->expr), "ptrtemp");
       gfc_add_modify (&lse->pre, tmp, rse->expr);
@@ -10242,7 +10248,7 @@ gfc_trans_pointer_assignment (gfc_expr * expr1, gfc_expr * expr2)
       if (non_proc_ptr_assign && expr1->ts.type == BT_CLASS)
 	{
 	  trans_class_vptr_len_assignment (&block, expr1, expr2, &rse, NULL,
-					   NULL);
+					   NULL, NULL);
 	  lse.expr = gfc_class_data_get (lse.expr);
 	}
 
@@ -10371,7 +10377,8 @@ gfc_trans_pointer_assignment (gfc_expr * expr1, gfc_expr * expr2)
 	      if (expr1->ts.type == BT_CLASS)
 		expr1_vptr = trans_class_vptr_len_assignment (&block, expr1,
 							      expr2, &rse,
-							      NULL, NULL);
+							      NULL, NULL,
+							      NULL);
 	    }
 	}
       else if (expr2->expr_type == EXPR_VARIABLE)
@@ -10388,7 +10395,7 @@ gfc_trans_pointer_assignment (gfc_expr * expr1, gfc_expr * expr2)
 	      rse.expr = NULL_TREE;
 	      rse.string_length = strlen_rhs;
 	      trans_class_vptr_len_assignment (&block, expr1, expr2, &rse,
-					       NULL, NULL);
+					       NULL, NULL, NULL);
 	    }
 
 	  if (remap == NULL)
@@ -10421,7 +10428,7 @@ gfc_trans_pointer_assignment (gfc_expr * expr1, gfc_expr * expr2)
 	    {
 	      expr1_vptr = trans_class_vptr_len_assignment (&block, expr1,
 							    expr2, &rse, NULL,
-							    NULL);
+							    NULL, NULL);
 	      gfc_add_block_to_block (&block, &rse.pre);
 	      tmp = gfc_create_var (TREE_TYPE (rse.expr), "ptrtemp");
 	      gfc_add_modify (&lse.pre, tmp, rse.expr);
@@ -11819,7 +11826,7 @@ trans_class_assignment (stmtblock_t *block, gfc_expr *lhs, gfc_expr *rhs,
 			gfc_se *lse, gfc_se *rse, bool use_vptr_copy,
 			bool class_realloc)
 {
-  tree tmp, fcn, stdcopy, to_len, from_len, vptr, old_vptr;
+  tree tmp, fcn, stdcopy, to_len, from_len, vptr, old_vptr, rhs_vptr;
   vec<tree, va_gc> *args = NULL;
   bool final_expr;
 
@@ -11843,7 +11850,9 @@ trans_class_assignment (stmtblock_t *block, gfc_expr *lhs, gfc_expr *rhs,
     }
 
   vptr = trans_class_vptr_len_assignment (block, lhs, rhs, rse, &to_len,
-					 &from_len);
+					  &from_len, &rhs_vptr);
+  if (rhs_vptr == NULL_TREE)
+    rhs_vptr = vptr;
 
   /* Generate (re)allocation of the lhs.  */
   if (class_realloc)
@@ -11856,7 +11865,7 @@ trans_class_assignment (stmtblock_t *block, gfc_expr *lhs, gfc_expr *rhs,
       else
 	old_vptr = build_int_cst (TREE_TYPE (vptr), 0);
 
-      size = gfc_vptr_size_get (vptr);
+      size = gfc_vptr_size_get (rhs_vptr);
       tmp = lse->expr;
       class_han = GFC_CLASS_TYPE_P (TREE_TYPE (tmp))
 	  ? gfc_class_data_get (tmp) : tmp;
@@ -11870,12 +11879,14 @@ trans_class_assignment (stmtblock_t *block, gfc_expr *lhs, gfc_expr *rhs,
 
       /* Reallocate if dynamic types are different. */
       gfc_init_block (&re_alloc);
+      tmp = fold_convert (pvoid_type_node, class_han);
       re = build_call_expr_loc (input_location,
 				builtin_decl_explicit (BUILT_IN_REALLOC), 2,
-				fold_convert (pvoid_type_node, class_han),
-				size);
+				tmp, size);
+      re = fold_build2_loc (input_location, MODIFY_EXPR, TREE_TYPE (tmp), tmp,
+			    re);
       tmp = fold_build2_loc (input_location, NE_EXPR,
-			     logical_type_node, vptr, old_vptr);
+			     logical_type_node, rhs_vptr, old_vptr);
       re = fold_build3_loc (input_location, COND_EXPR, void_type_node,
 			    tmp, re, build_empty_stmt (input_location));
       gfc_add_expr_to_block (&re_alloc, re);
diff --git a/gcc/testsuite/gfortran.dg/asan/pr110415-2.f90 b/gcc/testsuite/gfortran.dg/asan/pr110415-2.f90
new file mode 100755
index 0000000..f4ff182
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/asan/pr110415-2.f90
@@ -0,0 +1,45 @@
+! { dg-do run }
+!
+! Contributed by Brad Richardson <everythingfunctional@protonmail.com>
+!
+implicit none
+  type, abstract :: p
+    integer :: a = 4
+  end type p
+
+  type, extends(p) :: c
+    integer :: b = 7
+    character(len=:), allocatable :: str, str2(:)
+  end type c
+
+  type, extends(p) :: d
+    integer :: ef = 7
+  end type d
+
+  class(p), allocatable :: a
+
+  a = func()
+
+  a = func2()
+
+  a = func()
+
+  deallocate(a)
+
+contains
+  function func2() result(a)
+    class(p), allocatable :: a
+    a = d()
+  end function func2
+
+  function func() result(a)
+    class(p), allocatable :: a
+
+    a = c()
+    select type(a)
+    type is (c)
+      a%str = 'abcd'
+      a%str2 = ['abcd','efgh']
+    end select
+  end function func
+end program
diff --git a/gcc/testsuite/gfortran.dg/asan/pr110415-3.f90 b/gcc/testsuite/gfortran.dg/asan/pr110415-3.f90
new file mode 100755
index 0000000..65c018d
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/asan/pr110415-3.f90
@@ -0,0 +1,49 @@
+! { dg-do run }
+!
+! Contributed by Brad Richardson <everythingfunctional@protonmail.com>
+!
+implicit none
+  type, abstract :: p
+    integer :: a = 4
+  end type p
+
+  type, extends(p) :: c
+    integer :: b = 7
+    character(len=:), allocatable :: str, str2(:)
+  end type c
+
+  type, extends(p) :: d
+    integer :: ef = 7
+  end type d
+
+  class(p), allocatable :: a(:)
+
+  a = func()
+
+  a = func2()
+
+  a = func()
+
+  deallocate(a)
+
+contains
+  function func2() result(a)
+    class(p), allocatable :: a(:)
+    a = [d(),d()]
+  end function func2
+
+  function func() result(a)
+    class(p), allocatable :: a(:)
+
+    a = [c(),c(),c()]
+    select type(a)
+    type is (c)
+      a(1)%str = 'abcd'
+      a(2)%str = 'abc'
+      a(3)%str = 'abcd4'
+      a(1)%str2 = ['abcd','efgh']
+      a(2)%str2 = ['bcd','fgh']
+      a(3)%str2 = ['abcd6','efgh7']
+    end select
+  end function func
+end program
diff --git a/gcc/testsuite/gfortran.dg/pr110415.f90 b/gcc/testsuite/gfortran.dg/pr110415.f90
new file mode 100644
index 0000000..f647cc4
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr110415.f90
@@ -0,0 +1,20 @@
+! { dg-do run }
+!
+! Contributed by Brad Richardson <everythingfunctional@protonmail.com>
+!
+  type, abstract :: p
+  end type p
+
+  type, extends(p) :: c
+  end type c
+
+  class(p), allocatable :: a
+
+  a = func()
+contains
+  function func() result(a)
+    class(p), allocatable :: a
+
+    a = c()
+  end function func
+end program