[DebugInfo][Support] Replace DWARFDataExtractor size function

This patch adds a new size function to the base DataExtractor class,
which removes the need for the DWARFDataExtractor size function.

It is unclear why DWARFDataExtractor's size function returned zero in
some circumstances (i.e. when it is constructed without a section, and
with a different data source instead), so that behaviour has changed.
The old behaviour could cause an assertion in the debug line parser, as
the size did not reflect the actual data available, and could be lower
than the current offset being parsed.

Reviewed by: dblaikie

Differential Revision: https://reviews.llvm.org/D72337

Author: jh7370

llvm/include/llvm/DebugInfo/DWARF/DWARFDataExtractor.h

@@ -55,8 +55,6 @@ class DWARFDataExtractor : public DataExtractor {
   /// reflect the absolute address of this pointer.
   Optional<uint64_t> getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
                                        uint64_t AbsPosOffset = 0) const;
-
-  size_t size() const { return Section == nullptr ? 0 : Section->Data.size(); }
 };
 
 } // end namespace llvm

llvm/include/llvm/Support/DataExtractor.h

@@ -534,14 +534,14 @@ class DataExtractor {
   /// error state of the cursor. The only way both eof and error states can be
   /// true is if one attempts a read while the cursor is at the very end of the
   /// data buffer.
-  bool eof(const Cursor &C) const { return Data.size() == C.Offset; }
+  bool eof(const Cursor &C) const { return size() == C.Offset; }
 
   /// Test the validity of \a offset.
   ///
   /// @return
   ///     \b true if \a offset is a valid offset into the data in this
   ///     object, \b false otherwise.
-  bool isValidOffset(uint64_t offset) const { return Data.size() > offset; }
+  bool isValidOffset(uint64_t offset) const { return size() > offset; }
 
   /// Test the availability of \a length bytes of data from \a offset.
   ///
@@ -563,6 +563,9 @@ class DataExtractor {
     return isValidOffsetForDataOfSize(offset, AddressSize);
   }
 
+  /// Return the number of bytes in the underlying buffer.
+  size_t size() const { return Data.size(); }
+
 protected:
   // Make it possible for subclasses to access these fields without making them
   // public.

llvm/unittests/Support/DataExtractorTest.cpp

@@ -269,4 +269,13 @@ TEST(DataExtractorTest, eof) {
   EXPECT_TRUE(DE.eof(C));
   EXPECT_THAT_ERROR(C.takeError(), Succeeded());
 }
+
+TEST(DataExtractorTest, size) {
+  uint8_t Data[] = {'A', 'B', 'C', 'D'};
+  DataExtractor DE1(StringRef(reinterpret_cast<char *>(Data), sizeof(Data)),
+                    false, 8);
+  EXPECT_EQ(DE1.size(), sizeof(Data));
+  DataExtractor DE2(ArrayRef<uint8_t>(Data), false, 8);
+  EXPECT_EQ(DE2.size(), sizeof(Data));
+}
 }