analyzer: remove offset_region size overloads [PR111266]

PR analyzer/111266 reports a missing -Wanalyzer-out-of-bounds when
accessing relative to a concrete byte offset.

Root cause is that offset_region::get_{byte,bit}_size_sval were
attempting to compute the size that's valid to access, rather than the
size of the access attempt.

Fixed by removing these vfunc overrides from offset_region as the
base class implementation does the right thing.

gcc/analyzer/ChangeLog:
	PR analyzer/111266
	* region.cc (offset_region::get_byte_size_sval): Delete.
	(offset_region::get_bit_size_sval): Delete.
	* region.h (region::get_byte_size): Add comment clarifying that
	this relates to the size of the access, rather than the size
	that's valid to access.
	(region::get_bit_size): Likewise.
	(region::get_byte_size_sval): Likewise.
	(region::get_bit_size_sval): Likewise.
	(offset_region::get_byte_size_sval): Delete.
	(offset_region::get_bit_size_sval): Delete.

gcc/testsuite/ChangeLog:
	PR analyzer/111266
	* c-c++-common/analyzer/out-of-bounds-pr111266.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

3 files changed, 23 insertions, 56 deletions

diff --git a/gcc/analyzer/region.cc b/gcc/analyzer/region.cc
index 249852a..50821a5 100644
--- a/gcc/analyzer/region.cc
+++ b/gcc/analyzer/region.cc
@@ -1990,54 +1990,6 @@ offset_region::get_relative_symbolic_offset (region_model_manager *mgr
   return get_byte_offset ();
 }
 
-/* Implementation of region::get_byte_size_sval vfunc for offset_region.  */
-
-const svalue *
-offset_region::get_byte_size_sval (region_model_manager *mgr) const
-{
-  tree offset_cst = get_byte_offset ()->maybe_get_constant ();
-  byte_size_t byte_size;
-  /* If the offset points in the middle of the region,
-     return the remaining bytes.  */
-  if (get_byte_size (&byte_size) && offset_cst)
-    {
-      byte_size_t offset = wi::to_offset (offset_cst);
-      byte_range r (0, byte_size);
-      if (r.contains_p (offset))
-	{
-	  tree remaining_byte_size = wide_int_to_tree (size_type_node,
-						       byte_size - offset);
-	  return mgr->get_or_create_constant_svalue (remaining_byte_size);
-	}
-    }
-
-  return region::get_byte_size_sval (mgr);
-}
-
-/* Implementation of region::get_bit_size_sval vfunc for offset_region.  */
-
-const svalue *
-offset_region::get_bit_size_sval (region_model_manager *mgr) const
-{
-  tree offset_cst = get_bit_offset (mgr)->maybe_get_constant ();
-  bit_size_t bit_size;
-  /* If the offset points in the middle of the region,
-     return the remaining bits.  */
-  if (get_bit_size (&bit_size) && offset_cst)
-    {
-      bit_size_t offset = wi::to_offset (offset_cst);
-      bit_range r (0, bit_size);
-      if (r.contains_p (offset))
-	{
-	  tree remaining_bit_size = wide_int_to_tree (size_type_node,
-						       bit_size - offset);
-	  return mgr->get_or_create_constant_svalue (remaining_bit_size);
-	}
-    }
-
-  return region::get_bit_size_sval (mgr);
-}
-
 /* class sized_region : public region.  */
 
 /* Implementation of region::accept vfunc for sized_region.  */
diff --git a/gcc/analyzer/region.h b/gcc/analyzer/region.h
index 3d3ff8e..70557ba 100644
--- a/gcc/analyzer/region.h
+++ b/gcc/analyzer/region.h
@@ -187,20 +187,28 @@ public:
 
   /* Attempt to get the size of this region as a concrete number of bytes.
      If successful, return true and write the size to *OUT.
-     Otherwise return false.  */
+     Otherwise return false.
+     This is the accessed size, not necessarily the size that's valid to
+     access.  */
   virtual bool get_byte_size (byte_size_t *out) const;
 
   /* Attempt to get the size of this region as a concrete number of bits.
      If successful, return true and write the size to *OUT.
-     Otherwise return false.  */
+     Otherwise return false.
+     This is the accessed size, not necessarily the size that's valid to
+     access.  */
   virtual bool get_bit_size (bit_size_t *out) const;
 
   /* Get a symbolic value describing the size of this region in bytes
-     (which could be "unknown").  */
+     (which could be "unknown").
+     This is the accessed size, not necessarily the size that's valid to
+     access.  */
   virtual const svalue *get_byte_size_sval (region_model_manager *mgr) const;
 
   /* Get a symbolic value describing the size of this region in bits
-     (which could be "unknown").  */
+     (which could be "unknown").
+     This is the accessed size, not necessarily the size that's valid to
+     access.  */
   virtual const svalue *get_bit_size_sval (region_model_manager *mgr) const;
 
   /* Attempt to get the offset in bits of this region relative to its parent.
@@ -978,10 +986,6 @@ public:
   bool get_relative_concrete_offset (bit_offset_t *out) const final override;
   const svalue *get_relative_symbolic_offset (region_model_manager *mgr)
     const final override;
-  const svalue * get_byte_size_sval (region_model_manager *mgr)
-    const final override;
-  const svalue * get_bit_size_sval (region_model_manager *mgr)
-    const final override;
 
 private:
   const svalue *m_byte_offset;
diff --git a/gcc/testsuite/c-c++-common/analyzer/out-of-bounds-pr111266.c b/gcc/testsuite/c-c++-common/analyzer/out-of-bounds-pr111266.c
new file mode 100644
index 0000000..cee3663
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/analyzer/out-of-bounds-pr111266.c
@@ -0,0 +1,11 @@
+#include <stdint.h>
+void *malloc (__SIZE_TYPE__);
+void free (void *);
+
+void test_binop2 ()
+{
+  char *p = (char *) malloc (4);
+  int32_t *i = (int32_t *) (p + 3);
+  *i = 20042; /* { dg-warning "heap-based buffer overflow" } */
+  free (p);
+}