[DWARF] Add a unit test for DWARFUnit::getLength().

[ikudrin]

Summary

This is a follow-up of D66472, where the return value of DWARFUnit::getLength() was changed from uint32_t to uint64_t.
The test checks that a unit header with Length > 4G can be successfully parsed and the value of the Length field is not truncated.

[probinson]

As written, this will work only for little-endian. There are other unittests that are bi-endian that you ought to be able to use for examples; if nothing else, bail out after checking sys::IsLittleEndianHost (but a bi-endian test would be better).

[dblaikie]

In D67276#1661066, @probinson wrote:

As written, this will work only for little-endian. There are other unittests that are bi-endian that you ought to be able to use for examples; if nothing else, bail out after checking sys::IsLittleEndianHost (but a bi-endian test would be better).

I'm not sure the host endianness is relevant here, though - the input data is hardcoded & the parsing hardcodes the endianness when it constructs the DWARFDataExtractor (the "true" parameter specifies little endian). So I /think/ this will work correctly/pass on a little or big endian host.

Testing both endiannesses seems unnecessary to me - since that's part of DataExtractor that's already/otherwise tested.

unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

3169–3175 ↗

(On Diff #219093)

This intermediate step seems unnecessary - DWARFContext is basically passing back the string you put into the map, right?

So maybe skipping all that and building the DWARFSEction around the StringRef around DebugInfoSecRaw and passing that into the DWARFDataExtractor.

[ikudrin]

unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

3169–3175 ↗

(On Diff #219093)

But we still need a DWARFContext to pass to Header.extract(), and we also need a DWARFObject to pass to DWARFDataExtractor, right? So, we can eliminate only the call to Obj.forEachInfoSection(), replacing it with an artificial DWARFSection, which does not seem much.

[dblaikie]

Looks good to me - thanks!

unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

3169–3175 ↗

(On Diff #219093)

Ah, fair enough!

llvm/trunk/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

TEST(DWARFDebugInfo, TestDWARFDieRangeInfoIntersects) {
   AssertRangesIntersect(Ranges, {{0x3f, 0x40}});
   // Test range that starts at end of second range
   AssertRangesDontIntersect(Ranges, {{0x40, 0x41}});
 
   AssertRangesDontIntersect(Ranges, {{0x20, 0x21}, {0x2f, 0x30}});
   AssertRangesIntersect(Ranges, {{0x20, 0x21}, {0x2f, 0x31}});
 }
 
+TEST(DWARFDebugInfo, TestDWARF64UnitLength) {
+  static const char DebugInfoSecRaw[] =
+      "\xff\xff\xff\xff"                 // DWARF64 mark
+      "\x88\x77\x66\x55\x44\x33\x22\x11" // Length
+      "\x05\x00"                         // Version
+      "\x01"                             // DW_UT_compile
+      "\x04"                             // Address size
+      "\0\0\0\0\0\0\0\0";                // Offset Into Abbrev. Sec.
+  StringMap<std::unique_ptr<MemoryBuffer>> Sections;
+  Sections.insert(std::make_pair(
+      "debug_info", MemoryBuffer::getMemBuffer(
+                        StringRef(DebugInfoSecRaw, sizeof(DebugInfoSecRaw)))));
+  auto Context = DWARFContext::create(Sections, /* AddrSize = */ 4,
+                                      /* isLittleEndian = */ true);
+  const auto &Obj = Context->getDWARFObj();
+  Obj.forEachInfoSections([&](const DWARFSection &Sec) {
+    DWARFUnitHeader Header;
+    DWARFDataExtractor Data(Obj, Sec, /* IsLittleEndian = */ true,
+                            /* AddressSize = */ 4);
+    uint64_t Offset = 0;
+    EXPECT_FALSE(Header.extract(*Context, Data, &Offset));
+    // Header.extract() returns false because there is not enough space
+    // in the section for the declared length. Anyway, we can check that
+    // the properties are read correctly.
+    ASSERT_EQ(DwarfFormat::DWARF64, Header.getFormat());
+    ASSERT_EQ(0x1122334455667788ULL, Header.getLength());
+    ASSERT_EQ(5, Header.getVersion());
+    ASSERT_EQ(DW_UT_compile, Header.getUnitType());
+    ASSERT_EQ(4, Header.getAddressByteSize());
+
+    // Check that the length can be correctly read in the unit class.
+    DWARFUnitVector DummyUnitVector;
+    DWARFSection DummySec;
+    DWARFCompileUnit CU(*Context, Sec, Header, /* DA = */ 0, /* RS = */ 0,
+                        /* LocSection = */ 0, /* SS = */ StringRef(),
+                        /* SOS = */ DummySec, /* AOS = */ 0,
+                        /* LS = */ DummySec, /* LE = */ true,
+                        /* isDWO= */ false, DummyUnitVector);
+    ASSERT_EQ(0x1122334455667788ULL, CU.getLength());
+  });
+}
+
 } // end anonymous namespace