[lldb] UpdateFormatsIfNeeded should respect the dynamic value type

[augusto2112]

UpdateFormatsIfNeeded has hardcoded the call to GetFormat with no dynamic values. GetFormat will try to find the synthetic children of the ValueObject, and passing the wrong one can fail, which can be bad for performance but should not be user visible. Fix the performace bug by passing the dynamic value type of the ValueObject.

rdar://122506593

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Augusto Noronha (augusto2112)

Changes

UpdateFormatsIfNeeded has hardcoded the call to GetFormat with no dynamic values. GetFormat will try to find the synthetic children of the ValueObject, and passing the wrong one can fail, which can be bad for performance but should not be user visible. Fix the performace bug by passing the dynamic value type of the ValueObject.

rdar://122506593

---

Full diff: https://github.com/llvm/llvm-project/pull/93262.diff

1 Files Affected:

• (modified) lldb/source/Core/ValueObject.cpp (+1-1)

diff --git a/lldb/source/Core/ValueObject.cpp b/lldb/source/Core/ValueObject.cpp
index 1443d9dfc3280..c5c434a941b34 100644
--- a/lldb/source/Core/ValueObject.cpp
+++ b/lldb/source/Core/ValueObject.cpp
@@ -216,7 +216,7 @@ bool ValueObject::UpdateFormatsIfNeeded() {
     m_last_format_mgr_revision = DataVisualization::GetCurrentRevision();
     any_change = true;
 
-    SetValueFormat(DataVisualization::GetFormat(*this, eNoDynamicValues));
+    SetValueFormat(DataVisualization::GetFormat(*this, GetDynamicValueType()));
     SetSummaryFormat(
         DataVisualization::GetSummaryFormat(*this, GetDynamicValueType()));
     SetSyntheticChildren(

[jimingham]

I wish I knew why the original code was ignoring GetDynamicValueType here, when it does use it on the very next line... The old code looks wrong to me. However, the places where dynamic values matter for the Format choice are uncommon - you generally set formats on scalars, and scalars don't have dynamic types... So maybe this was just an expression of "how could this matter"?

In any case, this does seem more correct on the face of it.