Patchwork [fortran] PR54107 ICE on recursive interface

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Submitter Mikael Morin
Date Feb. 7, 2013, 10:28 p.m.
Message ID <51142A89.8040409@sfr.fr>
Download mbox | patch
Permalink /patch/219010/
State New
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Comments

Mikael Morin - Feb. 7, 2013, 10:28 p.m.
Hello,

this is the last remaining patch to fix an infinite recursion when
creating the middle-end type of a function having a dummy
procedure whose interface is the function itself.
This patch is a slight variation of the comment 4 fix that was attached
to the PR.  It sets the procedure's backend_decl to error_mark_node, so
that the recursion can be detected and handled in the next iteration.  I
don't think the middle-end supports recursive function types, so the
middle-end types for recursive dummy procedure are actually variadic
procedure types.

regression tested on x86_64-unknown-linux-gnu. OK for trunk?
2013-02-07  Mikael Morin  <mikael@gcc.gnu.org>

	PR fortran/54107
	* trans-types.c (gfc_get_function_type): Change a NULL backend_decl
	to error_mark_node on entry.  Detect recursive types.  Build a variadic
	procedure type if the type is recursive.  Restore the initial
	backend_decl.

2013-02-07  Mikael Morin  <mikael@gcc.gnu.org>

	PR fortran/54107
	* gfortran.dg/recursive_interface_2.f90: New test.
Paul Richard Thomas - Feb. 8, 2013, 1:06 p.m.
Mikael,

The patch itself is good for trunk - it's rather clever, in fact :-)

What's happened to the testcase?  There are still lots of commented
out lines that I presume are fixed.

Cheers

Paul

On 7 February 2013 23:28, Mikael Morin <mikael.morin@sfr.fr> wrote:
> Hello,
>
> this is the last remaining patch to fix an infinite recursion when
> creating the middle-end type of a function having a dummy
> procedure whose interface is the function itself.
> This patch is a slight variation of the comment 4 fix that was attached
> to the PR.  It sets the procedure's backend_decl to error_mark_node, so
> that the recursion can be detected and handled in the next iteration.  I
> don't think the middle-end supports recursive function types, so the
> middle-end types for recursive dummy procedure are actually variadic
> procedure types.
>
> regression tested on x86_64-unknown-linux-gnu. OK for trunk?
>
>



--
The knack of flying is learning how to throw yourself at the ground and miss.
       --Hitchhikers Guide to the Galaxy

Patch

diff --git a/trans-types.c b/trans-types.c
index 21aa75c..360c782 100644
--- a/trans-types.c
+++ b/trans-types.c
@@ -2711,19 +2711,23 @@  gfc_get_function_type (gfc_symbol * sym)
   gfc_formal_arglist *f;
   gfc_symbol *arg;
   int alternate_return;
-  bool is_varargs = true;
+  bool is_varargs = true, recursive_type = false;
 
   /* Make sure this symbol is a function, a subroutine or the main
      program.  */
   gcc_assert (sym->attr.flavor == FL_PROCEDURE
 	      || sym->attr.flavor == FL_PROGRAM);
 
-  if (sym->backend_decl)
-    {
-      if (sym->attr.proc_pointer)
-	return TREE_TYPE (TREE_TYPE (sym->backend_decl));
-      return TREE_TYPE (sym->backend_decl);
-    }
+  /* To avoid recursing infinitely on recrusive types, we use error_mark_node
+     so that they can be detected here and handled further down.  */
+  if (sym->backend_decl == NULL)
+    sym->backend_decl = error_mark_node;
+  else if (sym->backend_decl == error_mark_node)
+    recursive_type = true;
+  else if (sym->attr.proc_pointer)
+    return TREE_TYPE (TREE_TYPE (sym->backend_decl));
+  else
+    return TREE_TYPE (sym->backend_decl);
 
   alternate_return = 0;
   typelist = NULL;
@@ -2775,6 +2779,13 @@  gfc_get_function_type (gfc_symbol * sym)
 
 	  if (arg->attr.flavor == FL_PROCEDURE)
 	    {
+	      /* We don't know in the general case which argument causes
+		 recursion.  But we know that it is a procedure.  So we give up
+		 creating the procedure argument type list at the first
+		 procedure argument.  */
+	      if (recursive_type)
+	        goto arg_type_list_done;
+
 	      type = gfc_get_function_type (arg);
 	      type = build_pointer_type (type);
 	    }
@@ -2828,6 +2839,11 @@  gfc_get_function_type (gfc_symbol * sym)
       || sym->attr.if_source != IFSRC_UNKNOWN)
     is_varargs = false;
 
+arg_type_list_done:
+
+  if (!recursive_type && sym->backend_decl == error_mark_node)
+    sym->backend_decl = NULL_TREE;
+
   if (alternate_return)
     type = integer_type_node;
   else if (!sym->attr.function || gfc_return_by_reference (sym))
@@ -2865,7 +2881,7 @@  gfc_get_function_type (gfc_symbol * sym)
   else
     type = gfc_sym_type (sym);
 
-  if (is_varargs)
+  if (is_varargs || recursive_type)
     type = build_varargs_function_type_vec (type, typelist);
   else
     type = build_function_type_vec (type, typelist);