[Bug middle-end/17044] [3.5 Regression] libgcc2.c:169: internal compiler error: Segmentation fault

["dave at hiauly1 dot hia dot nrc dot ca" <gcc-bugzilla@gcc.gnu.org>]

------- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca  2004-08-17 20:49 -------
Subject: Re:  [3.5 Regression] libgcc2.c:169: internal c

> The exception occurs in the following call to free:
> 
> Breakpoint 13, 0x400000000031e350 in thread_block (bb=0x800003fffeacd8c0)
>     at ../../gcc/gcc/tree-ssa-threadupdate.c:381
> 381           free (rd);

Here is a possible fix.  VARRAY_GENERIC_PTR_INIT allocates with
garbage collection enabled.  The code as written was trying to
free the i=0 block allocated using ggc_alloc (i.e., mmap allocated).
This patch leaves collection to the garbage collector.

I will post to gcc-patches when testing completes.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6602)

2004-08-17  John David Anglin  <dave.anglin@nrc-cnrc.gc.ca>

	PR middle-end/17044
	* tree-ssa-threadupdate.c (redirection_data): Make static.
	(thread_block): Use ggc_alloc_cleared to allocate struct
	redirection_data.  Don't free elements in redirection_data.

Index: tree-ssa-threadupdate.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-threadupdate.c,v
retrieving revision 2.1
diff -u -3 -p -r2.1 tree-ssa-threadupdate.c
--- tree-ssa-threadupdate.c	9 Aug 2004 19:13:07 -0000	2.1
+++ tree-ssa-threadupdate.c	17 Aug 2004 20:15:35 -0000
@@ -92,6 +92,9 @@ struct redirection_data
   edge outgoing_edge;
 };
 
+/* Main data structure to hold information for duplicates of BB.  */
+static varray_type redirection_data;
+
 /* For each PHI node in BB, find or create a PHI node in NEW_BB for the
    same PHI_RESULT.  Add an argument to the PHI node in NEW_BB which
    corresponds to the same PHI argument associated with edge E in BB.  */
@@ -239,8 +242,6 @@ thread_block (basic_block bb)
      be threaded to a duplicate of BB.  */
   bool all = true;
 
-  /* Main data structure to hold information for duplicates of BB.  */
-  varray_type redirection_data;
   unsigned int i;
 
   VARRAY_GENERIC_PTR_INIT (redirection_data, 2, "redirection data");
@@ -278,7 +279,7 @@ thread_block (basic_block bb)
 	    {
 	      struct redirection_data *rd;
 
-	      rd = xcalloc (1, sizeof (redirection_data));
+	      rd = ggc_alloc_cleared (sizeof (struct redirection_data));
 	      rd->outgoing_edge = e->aux;
 	      VARRAY_PUSH_GENERIC_PTR (redirection_data, rd);
 	    }
@@ -372,14 +373,7 @@ thread_block (basic_block bb)
       remove_last_stmt_and_useless_edges (bb, rd->outgoing_edge->dest);
     }
 
-  /* Done with this block.  Free any memory we have allocated, clear
-     REDIRECTION_DATA and unmark this block as needing incoming
-     edge redirections.  */
-  for (i = 0; i < VARRAY_ACTIVE_SIZE (redirection_data); i++)
-    {
-      struct redirection_data *rd = VARRAY_GENERIC_PTR (redirection_data, i);
-      free (rd);
-    }
+  /* Done with this block.  Clear REDIRECTION_DATA.  */
   VARRAY_CLEAR (redirection_data);
 }
 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17044