[lld] [llvm] [Symbolizer] Support for Missing Line Numbers. (PR #82240)

[via llvm-commits]

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@@ -1337,7 +1339,17 @@ uint32_t DWARFDebugLine::LineTable::lookupAddressImpl(
                                       DWARFDebugLine::Sequence::orderByHighPC);
   if (It == Sequences.end() || It->SectionIndex != Address.SectionIndex)
     return UnknownRowIndex;
-  return findRowInSeq(*It, Address);
+
+  uint32_t RowIndex = findRowInSeq(*It, Address);
+  if (RowIndex != UnknownRowIndex && DWARFDebugLine::ReportApproximateLine) {
+    for (uint32_t ApproxRowIndex = RowIndex;
+         ApproxRowIndex >= It->FirstRowIndex; --ApproxRowIndex) {
+      if (Rows[ApproxRowIndex].Line)
+        return ApproxRowIndex;
+      *IsApproximateLine = true;
+    }
+  }
+  return RowIndex;
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ampandey-1995 wrote:

> I think it might be clearer to have the early return, rather than having the non-approximate case come out through this for loop?

Yes added the logic of early return.

> ```
> if (RowIndex != UnknownRowIndex || !ReportApproximateLine)
>   return RowIndex;
I think the code for early return should match like this.
``` if (RowIndex != UnknownRowIndex || !ReportApproximateLine)
    return RowIndex```

> for (...) {
>   if (Rows[ApproxRowIndex].Line) {
>     *IsApproximateLine = true;
>     return ApproxRowIndex;
>   }
> }
> return RowIndex;
> ```
> Also, this will ensure that `(approximate)` isn't printed if the approximation doesn't find a non-zero line number (might be worth adding a test for that to demonstrate the fix/change in behavior here).

Yes, the current revision checks if the approximate loop code fails to get a suitable line number then it will return the orignal computed RowIndex.

Although, I would consider if you can help me with a hint to cover this with a test case. I am not sure how to do it in lit test case. Any Suggestions?


https://github.com/llvm/llvm-project/pull/82240