[PATCH] D101892: [DebugInfo] UnwindTable::create() should not add empty rows to CFI unwind table

[Venkata Ramanaiah Nalamothu via Phabricator via llvm-commits]

RamNalamothu updated this revision to Diff 343225.
RamNalamothu added a comment.

Made the suggested code changes.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101892/new/

https://reviews.llvm.org/D101892

Files:
  llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
  llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp


Index: llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
===================================================================
--- llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
+++ llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
@@ -447,6 +447,45 @@
   expectDumpResult(Locs, "");
 }
 
+// Here we test that empty rows are not added to UnwindTable when
+// dwarf::CIE::CFIs or dwarf::FDE::CFIs is empty.
+TEST(DWARFDebugFrame, UnwindTableEmptyRows) {
+  dwarf::CIE TestCIE = createCIE(/*IsDWARF64=*/false,
+                                 /*Offset=*/0x0,
+                                 /*Length=*/0xff);
+
+  // Having an empty instructions list is fine.
+  EXPECT_THAT_ERROR(parseCFI(TestCIE, {}), Succeeded());
+  EXPECT_TRUE(TestCIE.cfis().empty());
+
+  // Verify dwarf::UnwindTable::create() won't result in errors and
+  // and empty rows are not added to CIE UnwindTable.
+  Expected<dwarf::UnwindTable> RowsOrErr = dwarf::UnwindTable::create(&TestCIE);
+  EXPECT_THAT_ERROR(RowsOrErr.takeError(), Succeeded());
+  const size_t ExpectedNumOfRows = 0;
+  EXPECT_EQ(RowsOrErr->size(), ExpectedNumOfRows);
+
+  dwarf::FDE TestFDE(/*IsDWARF64=*/true,
+                     /*Offset=*/0x3333abcdabcd,
+                     /*Length=*/0x4444abcdabcd,
+                     /*CIEPointer=*/0x1111abcdabcd,
+                     /*InitialLocation=*/0x1000,
+                     /*AddressRange=*/0x1000,
+                     /*Cie=*/&TestCIE,
+                     /*LSDAAddress=*/None,
+                     /*Arch=*/Triple::x86_64);
+
+  // Having an empty instructions list is fine.
+  EXPECT_THAT_ERROR(parseCFI(TestFDE, {}), Succeeded());
+  EXPECT_TRUE(TestFDE.cfis().empty());
+
+  // Verify dwarf::UnwindTable::create() won't result in errors and
+  // and empty rows are not added to FDE UnwindTable.
+  RowsOrErr = dwarf::UnwindTable::create(&TestFDE);
+  EXPECT_THAT_ERROR(RowsOrErr.takeError(), Succeeded());
+  EXPECT_EQ(RowsOrErr->size(), ExpectedNumOfRows);
+}
+
 TEST(DWARFDebugFrame, UnwindTableErrorNonAscendingFDERows) {
   dwarf::CIE TestCIE = createCIE(/*IsDWARF64=*/false,
                                  /*Offset=*/0x0,
Index: llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
===================================================================
--- llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
+++ llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
@@ -196,17 +196,20 @@
 }
 
 Expected<UnwindTable> UnwindTable::create(const FDE *Fde) {
-  UnwindTable UT;
-  UnwindRow Row;
-  Row.setAddress(Fde->getInitialLocation());
-  UT.EndAddress = Fde->getInitialLocation() + Fde->getAddressRange();
-
   const CIE *Cie = Fde->getLinkedCIE();
   if (Cie == nullptr)
     return createStringError(errc::invalid_argument,
                              "unable to get CIE for FDE at offset 0x%" PRIx64,
                              Fde->getOffset());
 
+  // Rows will be empty if there are no CFI instructions.
+  if (Cie->cfis().empty() && Fde->cfis().empty())
+    return UnwindTable();
+
+  UnwindTable UT;
+  UnwindRow Row;
+  Row.setAddress(Fde->getInitialLocation());
+  UT.EndAddress = Fde->getInitialLocation() + Fde->getAddressRange();
   if (Error CieError = UT.parseRows(Cie->cfis(), Row, nullptr))
     return std::move(CieError);
   // We need to save the initial locations of registers from the CIE parsing
@@ -219,6 +222,10 @@
 }
 
 Expected<UnwindTable> UnwindTable::create(const CIE *Cie) {
+  // Rows will be empty if there are no CFI instructions.
+  if (Cie->cfis().empty())
+    return UnwindTable();
+
   UnwindTable UT;
   UnwindRow Row;
   if (Error CieError = UT.parseRows(Cie->cfis(), Row, nullptr))


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