Fix for issue 4638 in bitmap builder.

runtime/vm/bitmap.cc

Index: runtime/vm/bitmap.cc
===================================================================
--- runtime/vm/bitmap.cc	(revision 23602)
+++ runtime/vm/bitmap.cc	(working copy)
@@ -32,7 +32,9 @@
 
 
 bool BitmapBuilder::Get(intptr_t bit_offset) const {
-  ASSERT(InRange(bit_offset));
+  if (!InRange(bit_offset)) {
+    return false;
+  }
   intptr_t byte_offset = bit_offset >> kBitsPerByteLog2;
   // Bits not covered by the backing store are implicitly false.
   return (byte_offset < data_size_in_bytes_) && GetBit(bit_offset);
@@ -47,6 +49,10 @@
     if (!value) return;
     // Grow the backing store if necessary.
     intptr_t byte_offset = bit_offset >> kBitsPerByteLog2;
+    if (byte_offset > kSmiMax) {
+      FATAL1("Fatal error in BitmapBuilder::Set : invalid bit_offset, %"Pd"\n",
+             bit_offset);
+    }
     if (byte_offset >= data_size_in_bytes_) {
       uint8_t* old_data = data_;
       intptr_t old_size = data_size_in_bytes_;
@@ -72,7 +78,9 @@
 
 
 bool BitmapBuilder::GetBit(intptr_t bit_offset) const {
-  ASSERT(InRange(bit_offset));
+  if (!InRange(bit_offset)) {
+    return false;
+  }
   intptr_t byte_offset = bit_offset >> kBitsPerByteLog2;
   ASSERT(byte_offset < data_size_in_bytes_);
   intptr_t bit_remainder = bit_offset & (kBitsPerByte - 1);
@@ -83,7 +91,9 @@
 
 
 void BitmapBuilder::SetBit(intptr_t bit_offset, bool value) {
-  ASSERT(InRange(bit_offset));
+  if (!InRange(bit_offset)) {
+    return;

[srdjan, 2013/06/05 15:57:21]

FATAL instead of return

[siva, 2013/06/05 16:22:09]

Done.

+  }
   int byte_offset = bit_offset >> kBitsPerByteLog2;
   ASSERT(byte_offset < data_size_in_bytes_);
   int bit_remainder = bit_offset & (kBitsPerByte - 1);