Miscellaneous fixes for big-endian systems

This patch fixes a bunch of issues that show up on big-endian systems:

- The gnu_libstdcpp.py script doesn't follow the way libstdc++ encodes
  bit vectors: it should identify the enclosing *word* and then access
  the appropriate bit within that word.  Instead, the script simply
  operates on bytes.  This gives the same result on little-endian
  systems, but not on big-endian.

- lldb_private::formatters::WCharSummaryProvider always assumes wchar_t
  is UTF16, even though it could also be UTF8 or UTF32.  This is mostly
  not an issue on little-endian systems, but immediately fails on BE.
  Fixed by checking the size of wchar_t like WCharStringSummaryProvider
  already does.

- ClangASTContext::GetChildCompilerTypeAtIndex uses uint32_t to access
  the virtual base offset stored in the vtable, even though the size
  of this field matches the target pointer size according to the C++
  ABI.  Again, this is mostly not visible on LE, but fails on BE.

- Process::ReadStringFromMemory uses strncmp to search for a terminator
  consisting of multiple zero bytes.  This doesn't work since strncmp
  will stop already at the first zero byte.  Use memcmp instead.

Differential Revision: http://reviews.llvm.org/D18983

llvm-svn: 266313

lldb/examples/synthetic/gnu_libstdcpp.py

@@ -237,11 +237,12 @@ class StdVectorSynthProvider:
 		def get_child_at_index(self, index):
 			if index >= self.num_children():
 				return None
-			byte_offset = index / 8
-			bit_offset = index % 8
-			element_size = self.start_p.GetType().GetPointeeType().GetByteSize()
-			data = self.start_p.GetPointeeData(byte_offset / element_size)
-			bit = data.GetUnsignedInt8(lldb.SBError(), byte_offset % element_size) & (1 << bit_offset)
+			element_type = self.start_p.GetType().GetPointeeType()
+			element_bits = 8 * element_type.GetByteSize()
+			element_offset = index / element_bits
+			bit_offset = index % element_bits
+			element = self.start_p.CreateChildAtOffset('['+str(index)+']',element_offset,element_type)
+			bit = element.GetValueAsUnsigned(0) & (1 << bit_offset)
 			if bit != 0:
 				value_expr = "(bool)true"
 			else:

lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp

@@ -192,6 +192,14 @@ lldb_private::formatters::WCharSummaryProvider (ValueObject& valobj, Stream& str
     if (error.Fail())
         return false;
     
+    // Get a wchar_t basic type from the current type system
+    CompilerType wchar_compiler_type = valobj.GetCompilerType().GetBasicTypeFromAST(lldb::eBasicTypeWChar);
+
+    if (!wchar_compiler_type)
+        return false;
+
+    const uint32_t wchar_size = wchar_compiler_type.GetBitSize(nullptr); // Safe to pass NULL for exe_scope here
+
     StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
     options.SetData(data);
     options.SetStream(&stream);
@@ -200,5 +208,17 @@ lldb_private::formatters::WCharSummaryProvider (ValueObject& valobj, Stream& str
     options.SetSourceSize(1);
     options.SetBinaryZeroIsTerminator(false);
     
-    return StringPrinter::ReadBufferAndDumpToStream<StringPrinter::StringElementType::UTF16>(options);
+    switch (wchar_size)
+    {
+        case 8:
+            return StringPrinter::ReadBufferAndDumpToStream<StringPrinter::StringElementType::UTF8>(options);
+        case 16:
+            return StringPrinter::ReadBufferAndDumpToStream<StringPrinter::StringElementType::UTF16>(options);
+        case 32:
+            return StringPrinter::ReadBufferAndDumpToStream<StringPrinter::StringElementType::UTF32>(options);
+        default:
+            stream.Printf("size for wchar_t is not valid");
+            return true;
+    }
+    return true;
 }

lldb/source/Symbol/ClangASTContext.cpp

@@ -6075,8 +6075,9 @@ ClangASTContext::GetChildCompilerTypeAtIndex (lldb::opaque_compiler_type_t type,
                                                         {
                                                             clang::CharUnits base_offset_offset = itanium_vtable_ctx->getVirtualBaseOffsetOffset(cxx_record_decl, base_class_decl);
                                                             const lldb::addr_t base_offset_addr = vtable_ptr + base_offset_offset.getQuantity();
-                                                            const uint32_t base_offset = process->ReadUnsignedIntegerFromMemory(base_offset_addr, 4, UINT32_MAX, err);
-                                                            if (base_offset != UINT32_MAX)
+                                                            const uint32_t base_offset_size = process->GetAddressByteSize();
+                                                            const uint64_t base_offset = process->ReadUnsignedIntegerFromMemory(base_offset_addr, base_offset_size, UINT32_MAX, err);
+                                                            if (base_offset < UINT32_MAX)
                                                             {
                                                                 handled = true;
                                                                 bit_offset = base_offset * 8;

lldb/source/Target/Process.cpp

@@ -2437,7 +2437,7 @@ Process::ReadStringFromMemory (addr_t addr, char *dst, size_t max_bytes, Error &
             // Search for a null terminator of correct size and alignment in bytes_read
             size_t aligned_start = total_bytes_read - total_bytes_read % type_width;
             for (size_t i = aligned_start; i + type_width <= total_bytes_read + bytes_read; i += type_width)
-                if (::strncmp(&dst[i], terminator, type_width) == 0)
+                if (::memcmp(&dst[i], terminator, type_width) == 0)
                 {
                     error.Clear();
                     return i;