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

1 files changed, 6 insertions, 5 deletions

diff --git a/lldb/examples/synthetic/gnu_libstdcpp.py b/lldb/examples/synthetic/gnu_libstdcpp.py
index b6bf42235ac..fe60edce7e3 100644
--- a/lldb/examples/synthetic/gnu_libstdcpp.py
+++ b/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: