Don't error for zero-length arange entries

Although the DWARF specification states that .debug_aranges entries
can't have length zero, these can occur in the wild. There's no
particular reason to enforce this part of the spec, since functionally
they have no impact. The patch removes the error and introduces a new
warning for premature terminator entries which does not stop parsing.

This is a relanding of cb3a598, adding the missing obj2yaml part
that was needed.

Fixes https://bugs.llvm.org/show_bug.cgi?id=46805. See also
https://reviews.llvm.org/D71932 which originally introduced the error.

Reviewed by: ikudrin, dblaikie, Higuoxing

Differential Revision: https://reviews.llvm.org/D85313

Author: jh7370

llvm/lib/DebugInfo/DWARF/DWARFDebugArangeSet.cpp

@@ -132,19 +132,20 @@ Error DWARFDebugArangeSet::extract(DWARFDataExtractor data,
 
   uint64_t end_offset = Offset + full_length;
   while (*offset_ptr < end_offset) {
+    uint64_t EntryOffset = *offset_ptr;
     arangeDescriptor.Address = data.getUnsigned(offset_ptr, HeaderData.AddrSize);
     arangeDescriptor.Length = data.getUnsigned(offset_ptr, HeaderData.AddrSize);
 
-    if (arangeDescriptor.Length == 0) {
-      // Each set of tuples is terminated by a 0 for the address and 0
-      // for the length.
-      if (arangeDescriptor.Address == 0 && *offset_ptr == end_offset)
+    // Each set of tuples is terminated by a 0 for the address and 0
+    // for the length.
+    if (arangeDescriptor.Length == 0 && arangeDescriptor.Address == 0) {
+      if (*offset_ptr == end_offset)
         return ErrorSuccess();
       return createStringError(
           errc::invalid_argument,
           "address range table at offset 0x%" PRIx64
-          " has an invalid tuple (length = 0) at offset 0x%" PRIx64,
-          Offset, *offset_ptr - tuple_size);
+          " has a premature terminator entry at offset 0x%" PRIx64,
+          Offset, EntryOffset);
     }
 
     ArangeDescriptors.push_back(arangeDescriptor);

llvm/unittests/DebugInfo/DWARF/DWARFDebugArangeSetTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
+#include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -166,24 +167,78 @@ TEST(DWARFDebugArangeSet, UnevenLength) {
       "of the tuple size");
 }
 
-TEST(DWARFDebugArangeSet, ZeroLengthEntry) {
+TEST(DWARFDebugArangeSet, ZeroAddressEntry) {
   static const char DebugArangesSecRaw[] =
-      "\x24\x00\x00\x00" // Length
+      "\x1c\x00\x00\x00" // Length
       "\x02\x00"         // Version
       "\x00\x00\x00\x00" // Debug Info Offset
       "\x04"             // Address Size
       "\x00"             // Segment Selector Size
       "\x00\x00\x00\x00" // Padding
       "\x00\x00\x00\x00" // Entry1: Address
       "\x01\x00\x00\x00" //         Length
+      "\x00\x00\x00\x00" // Termination tuple
+      "\x00\x00\x00\x00";
+  DWARFDataExtractor Extractor(
+      StringRef(DebugArangesSecRaw, sizeof(DebugArangesSecRaw) - 1),
+      /*IsLittleEndian=*/true,
+      /*AddressSize=*/4);
+  DWARFDebugArangeSet Set;
+  uint64_t Offset = 0;
+  ASSERT_THAT_ERROR(Set.extract(Extractor, &Offset),
+                    Succeeded());
+  auto Range = Set.descriptors();
+  auto Iter = Range.begin();
+  ASSERT_EQ(std::distance(Iter, Range.end()), 1u);
+  EXPECT_EQ(Iter->Address, 0u);
+  EXPECT_EQ(Iter->Length, 1u);
+}
+
+TEST(DWARFDebugArangeSet, ZeroLengthEntry) {
+  static const char DebugArangesSecRaw[] =
+      "\x1c\x00\x00\x00" // Length
+      "\x02\x00"         // Version
+      "\x00\x00\x00\x00" // Debug Info Offset
+      "\x04"             // Address Size
+      "\x00"             // Segment Selector Size
+      "\x00\x00\x00\x00" // Padding
+      "\x01\x00\x00\x00" // Entry1: Address
+      "\x00\x00\x00\x00" //         Length
+      "\x00\x00\x00\x00" // Termination tuple
+      "\x00\x00\x00\x00";
+  DWARFDataExtractor Extractor(
+      StringRef(DebugArangesSecRaw, sizeof(DebugArangesSecRaw) - 1),
+      /*IsLittleEndian=*/true,
+      /*AddressSize=*/4);
+  DWARFDebugArangeSet Set;
+  uint64_t Offset = 0;
+  ASSERT_THAT_ERROR(Set.extract(Extractor, &Offset),
+                    Succeeded());
+  auto Range = Set.descriptors();
+  auto Iter = Range.begin();
+  ASSERT_EQ(std::distance(Iter, Range.end()), 1u);
+  EXPECT_EQ(Iter->Address, 1u);
+  EXPECT_EQ(Iter->Length, 0u);
+}
+
+TEST(DWARFDebugArangesSet, PrematureTerminator) {
+  static const char DebugArangesSecRaw[] =
+      "\x24\x00\x00\x00" // Length
+      "\x02\x00"         // Version
+      "\x00\x00\x00\x00" // Debug Info Offset
+      "\x04"             // Address Size
+      "\x00"             // Segment Selector Size
+      "\x00\x00\x00\x00" // Padding
+      "\x00\x00\x00\x00" // Entry1: Premature
+      "\x00\x00\x00\x00" //         terminator
       "\x01\x00\x00\x00" // Entry2: Address
-      "\x00\x00\x00\x00" //         Length (invalid)
+      "\x01\x00\x00\x00" //         Length
       "\x00\x00\x00\x00" // Termination tuple
       "\x00\x00\x00\x00";
   ExpectExtractError(
       DebugArangesSecRaw,
-      "address range table at offset 0x0 has an invalid tuple (length = 0) "
-      "at offset 0x18");
+      "address range table at offset 0x0 has a premature "
+      "terminator entry at offset 0x10");
 }
 
 } // end anonymous namespace