[Lldb-commits] [PATCH] D83256: [lldb] Assert on unaligned load in DataExtractor

[Jonas Devlieghere via Phabricator via lldb-commits]

JDevlieghere created this revision.
JDevlieghere added reviewers: labath, clayborg.

Somehow UBSan would only report the unaligned load in `TestLinuxCore.py` when 
running the tests with reproducers. This patch adds an assert for the 
`GetDouble` and `GetFloat` method, which triggers regardless of UBSan.


Repository:
  rLLDB LLDB

https://reviews.llvm.org/D83256

Files:
  lldb/include/lldb/Utility/DataExtractor.h
  lldb/source/Utility/DataExtractor.cpp


Index: lldb/source/Utility/DataExtractor.cpp
===================================================================
--- lldb/source/Utility/DataExtractor.cpp
+++ lldb/source/Utility/DataExtractor.cpp
@@ -15,7 +15,6 @@
 
 #include "lldb/Utility/DataBuffer.h"
 #include "lldb/Utility/DataBufferHeap.h"
-#include "lldb/Utility/Endian.h"
 #include "lldb/Utility/LLDBAssert.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/Stream.h"
@@ -624,41 +623,11 @@
 }
 
 float DataExtractor::GetFloat(offset_t *offset_ptr) const {
-  typedef float float_type;
-  float_type val = 0.0;
-  const size_t src_size = sizeof(float_type);
-  const float_type *src =
-      static_cast<const float_type *>(GetData(offset_ptr, src_size));
-  if (src) {
-    if (m_byte_order != endian::InlHostByteOrder()) {
-      const uint8_t *src_data = reinterpret_cast<const uint8_t *>(src);
-      uint8_t *dst_data = reinterpret_cast<uint8_t *>(&val);
-      for (size_t i = 0; i < sizeof(float_type); ++i)
-        dst_data[sizeof(float_type) - 1 - i] = src_data[i];
-    } else {
-      val = *src;
-    }
-  }
-  return val;
+  return Get<float>(offset_ptr);
 }
 
 double DataExtractor::GetDouble(offset_t *offset_ptr) const {
-  typedef double float_type;
-  float_type val = 0.0;
-  const size_t src_size = sizeof(float_type);
-  const float_type *src =
-      static_cast<const float_type *>(GetData(offset_ptr, src_size));
-  if (src) {
-    if (m_byte_order != endian::InlHostByteOrder()) {
-      const uint8_t *src_data = reinterpret_cast<const uint8_t *>(src);
-      uint8_t *dst_data = reinterpret_cast<uint8_t *>(&val);
-      for (size_t i = 0; i < sizeof(float_type); ++i)
-        dst_data[sizeof(float_type) - 1 - i] = src_data[i];
-    } else {
-      val = *src;
-    }
-  }
-  return val;
+  return Get<double>(offset_ptr);
 }
 
 long double DataExtractor::GetLongDouble(offset_t *offset_ptr) const {
Index: lldb/include/lldb/Utility/DataExtractor.h
===================================================================
--- lldb/include/lldb/Utility/DataExtractor.h
+++ lldb/include/lldb/Utility/DataExtractor.h
@@ -9,6 +9,7 @@
 #ifndef LLDB_UTILITY_DATAEXTRACTOR_H
 #define LLDB_UTILITY_DATAEXTRACTOR_H
 
+#include "lldb/Utility/Endian.h"
 #include "lldb/lldb-defines.h"
 #include "lldb/lldb-enumerations.h"
 #include "lldb/lldb-forward.h"
@@ -20,6 +21,11 @@
 #include <stdint.h>
 #include <string.h>
 
+#ifndef __builtin_is_aligned
+#define __builtin_is_aligned(POINTER, BYTE_COUNT)                              \
+  (((uintptr_t)(const void *)(POINTER)) % (BYTE_COUNT) == 0)
+#endif
+
 namespace lldb_private {
 class Log;
 class Stream;
@@ -979,6 +985,28 @@
   }
 
 protected:
+  template <typename T> T Get(lldb::offset_t *offset_ptr) const {
+    constexpr size_t src_size = sizeof(T);
+
+    const T *src = static_cast<const T *>(GetData(offset_ptr, src_size));
+
+    if (!src)
+      return 0.0;
+
+    assert(__builtin_is_aligned(src, alignof(T)));
+
+    if (m_byte_order != endian::InlHostByteOrder()) {
+      T val = 0.0;
+      uint8_t *dst_data = reinterpret_cast<uint8_t *>(&val);
+      const uint8_t *src_data = reinterpret_cast<const uint8_t *>(src);
+      for (size_t i = 0; i < src_size; ++i)
+        dst_data[src_size - 1 - i] = src_data[i];
+      return val;
+    }
+
+    return *src;
+  }
+
   // Member variables
   const uint8_t *m_start; ///< A pointer to the first byte of data.
   const uint8_t

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