commit 01319e93abe3a4d3e722de4e849762ea54d12d70
author Bryan Chan <bryan.chan@ca.ibm.com> Thu May 19 13:51:20 2016 +0000
committer Bryan Chan <bryan.chan@ca.ibm.com> Thu May 19 13:51:20 2016 +0000
tree 1e6681400f5fead23cfc4270bc2b994a055a889d
parent cda1bd50488d0f0ded3e708c6c669cb259050fb3

Avoid an assertion failure when a bit field is extracted from a value of the same size.

Summary: One of the cases handled by ValueObjectChild::UpdateValue() uses the entire width of the parent's scalar value as the size of the child, and extracts the child by calling Scalar::ExtractBitfield(). This seems valid but APInt::trunc(), APInt::sext() and APInt::zext() assert that the bit field must not have the same size as the parent scalar. Replacing those calls with sextOrTrunc(), zextOrTrunc(), sextOrSelf() and zextOrSelf() fixes the assertion failures.

Reviewers: uweigand, labath

Subscribers: labath, lldb-commits

Differential Revision: http://reviews.llvm.org/D20355

llvm-svn: 270062

lldb/source/Core/Scalar.cpp

diff --git a/lldb/source/Core/Scalar.cpp b/lldb/source/Core/Scalar.cpp
index 2462a97..d3e9a75 100644
--- a/lldb/source/Core/Scalar.cpp
+++ b/lldb/source/Core/Scalar.cpp
@@ -2788,7 +2788,7 @@
         case Scalar::e_slonglong:
         case Scalar::e_sint128:
         case Scalar::e_sint256:
-            m_integer = m_integer.ashr(bit_offset).trunc(bit_size).sext(8 * GetByteSize());
+            m_integer = m_integer.ashr(bit_offset).sextOrTrunc(bit_size).sextOrSelf(8 * GetByteSize());
             return true;
 
         case Scalar::e_uint:
@@ -2796,7 +2796,7 @@
         case Scalar::e_ulonglong:
         case Scalar::e_uint128:
         case Scalar::e_uint256:
-            m_integer = m_integer.lshr(bit_offset).trunc(bit_size).zext(8 * GetByteSize());
+            m_integer = m_integer.lshr(bit_offset).zextOrTrunc(bit_size).zextOrSelf(8 * GetByteSize());
             return true;
     }
     return false;

lldb/unittests/Core/ScalarTest.cpp

diff --git a/lldb/unittests/Core/ScalarTest.cpp b/lldb/unittests/Core/ScalarTest.cpp
index 2a5643f..bf85f8e 100644
--- a/lldb/unittests/Core/ScalarTest.cpp
+++ b/lldb/unittests/Core/ScalarTest.cpp
@@ -79,3 +79,27 @@
     ASSERT_EQ((unsigned long long)a, a_scalar.ULongLong());
 }
 
+TEST(ScalarTest, ExtractBitfield)
+{
+    uint32_t len = sizeof(long long) * 8;
+
+    long long a1 = 0xf1f2f3f4f5f6f7f8LL;
+    long long b1 = 0xff1f2f3f4f5f6f7fLL;
+    Scalar s_scalar(a1);
+    ASSERT_TRUE(s_scalar.ExtractBitfield(0, 0));
+    ASSERT_EQ(0, memcmp(&a1, s_scalar.GetBytes(), sizeof(a1)));
+    ASSERT_TRUE(s_scalar.ExtractBitfield(len, 0));
+    ASSERT_EQ(0, memcmp(&a1, s_scalar.GetBytes(), sizeof(a1)));
+    ASSERT_TRUE(s_scalar.ExtractBitfield(len - 4, 4));
+    ASSERT_EQ(0, memcmp(&b1, s_scalar.GetBytes(), sizeof(b1)));
+
+    unsigned long long a2 = 0xf1f2f3f4f5f6f7f8ULL;
+    unsigned long long b2 = 0x0f1f2f3f4f5f6f7fULL;
+    Scalar u_scalar(a2);
+    ASSERT_TRUE(u_scalar.ExtractBitfield(0, 0));
+    ASSERT_EQ(0, memcmp(&a2, u_scalar.GetBytes(), sizeof(a2)));
+    ASSERT_TRUE(u_scalar.ExtractBitfield(len, 0));
+    ASSERT_EQ(0, memcmp(&a2, u_scalar.GetBytes(), sizeof(a2)));
+    ASSERT_TRUE(u_scalar.ExtractBitfield(len - 4, 4));
+    ASSERT_EQ(0, memcmp(&b2, u_scalar.GetBytes(), sizeof(b2)));
+}