Re: [PUSHED] Fix off-by-one storage problem in irange_allocator.

[Andrew MacLeod via Gcc-patches]

On 10/6/20 2:41 PM, Andreas Schwab wrote:
On Okt 06 2020, Andrew MacLeod via Gcc-patches wrote:
diff --git a/gcc/value-range.h b/gcc/value-range.h
index 7031a823138..02a952bf81f 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -668,13 +668,12 @@ irange_allocator::allocate (unsigned num_pairs)
    if (num_pairs < 2)
      num_pairs = 2;
  
-  struct newir {
-    irange range;
-    tree mem[2];
-  };
-  size_t nbytes = (sizeof (newir) + sizeof (tree) * 2 * (num_pairs - 1));
-  struct newir *r = (newir *) obstack_alloc (&m_obstack, nbytes);
-  return new (r) irange (r->mem, num_pairs);
+  size_t nbytes = sizeof (tree) * 2 * num_pairs;
+
+  // Allocate the irnge and  required memory for the vector
Typo: irange

Andreas.

Ha. Its all good now.     THIS is actually the final final FINAL patch 
which is going thru testing.


diff --git a/gcc/value-range.h b/gcc/value-range.h
index 7031a823138..63c96204cda 100644
--- a/gcc/value-range.h
+++ b/gcc/value-range.h
@@ -668,13 +668,12 @@ irange_allocator::allocate (unsigned num_pairs)
   if (num_pairs < 2)
     num_pairs = 2;
 
-  struct newir {
-    irange range;
-    tree mem[2];
-  };
-  size_t nbytes = (sizeof (newir) + sizeof (tree) * 2 * (num_pairs - 1));
-  struct newir *r = (newir *) obstack_alloc (&m_obstack, nbytes);
-  return new (r) irange (r->mem, num_pairs);
+  size_t nbytes = sizeof (tree) * 2 * num_pairs;
+
+  // Allocate the irange and required memory for the vector.
+  void *r = obstack_alloc (&m_obstack, sizeof (irange));
+  tree *mem = (tree *) obstack_alloc (&m_obstack, nbytes);
+  return new (r) irange (mem, num_pairs);
 }
 
 inline irange *