[llvm] [NFC][DebugInfo] Wrap DILineInfo return type with std::optional to handle missing debug info. (PR #129792)

[David Blaikie via llvm-commits]

================
@@ -1730,40 +1730,44 @@ DWARFContext::getLocalsForAddress(object::SectionedAddress Address) {
   return Result;
 }
 
-DILineInfo DWARFContext::getLineInfoForAddress(object::SectionedAddress Address,
-                                               DILineInfoSpecifier Spec) {
-  DILineInfo Result;
+std::optional<DILineInfo>
+DWARFContext::getLineInfoForAddress(object::SectionedAddress Address,
+                                    DILineInfoSpecifier Spec) {
   DWARFCompileUnit *CU = getCompileUnitForCodeAddress(Address.Address);
   if (!CU)
-    return Result;
+    return std::nullopt;
 
-  getFunctionNameAndStartLineForAddress(
+  DILineInfo Result;
+  bool HasDebugInfoForAddress = getFunctionNameAndStartLineForAddress(
       CU, Address.Address, Spec.FNKind, Spec.FLIKind, Result.FunctionName,
       Result.StartFileName, Result.StartLine, Result.StartAddress);
   if (Spec.FLIKind != FileLineInfoKind::None) {
     if (const DWARFLineTable *LineTable = getLineTableForUnit(CU)) {
-      LineTable->getFileLineInfoForAddress(
+      HasDebugInfoForAddress |= LineTable->getFileLineInfoForAddress(
           {Address.Address, Address.SectionIndex}, Spec.ApproximateLine,
           CU->getCompilationDir(), Spec.FLIKind, Result);
     }
   }
+  if (!HasDebugInfoForAddress)
+    return std::nullopt;
 
   return Result;
 }
 
-DILineInfo
+std::optional<DILineInfo>
 DWARFContext::getLineInfoForDataAddress(object::SectionedAddress Address) {
-  DILineInfo Result;
   DWARFCompileUnit *CU = getCompileUnitForDataAddress(Address.Address);
   if (!CU)
-    return Result;
+    return std::nullopt;
 
   if (DWARFDie Die = CU->getVariableForAddress(Address.Address)) {
+    DILineInfo Result;
     Result.FileName = Die.getDeclFile(FileLineInfoKind::AbsoluteFilePath);
     Result.Line = Die.getDeclLine();
+    return Result;
   }
 
-  return Result;
+  return std::nullopt;
----------------
dwblaikie wrote:

This seems to add the new behavior, right? the `getLineInfoForDataAddress` would now return different things depending on whether teh address is covered by debug info, or its covered but has line zero? 

If so, while the change might not change the behavior of llvm-symbolizer, I wouldn't consider this NFC (because this API is pretty significant - and additional functionality has been added to it) & this particular change would want to be tested at the API level, or this change should only go in along with the usage on the other side that exposes the functionality to be tested via llvm-symbolizer or similar.

https://github.com/llvm/llvm-project/pull/129792