[NFC][ntuple] add clarifying comment in RVariantField

root-project · Jun 3, 2024 · 0cf959e · 0cf959e
1 parent b8cf2f9
commit 0cf959e
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/tree/ntuple/v7/src/RField.cxx b/tree/ntuple/v7/src/RField.cxx
@@ -3281,6 +3281,8 @@ ROOT::Experimental::RVariantField::RVariantField(std::string_view fieldName,
       fVariantOffset = dm->GetOffset();
 
    const auto tagSize = GetVariantTagSize();
+   // To calculate the padding, we use the tag size as a substitute for the tag alignment, i.e. the next line
+   // calculates alignof(tagtype) - (fMaxItemSize % alignof(tagtype));
    const auto padding = tagSize - (fMaxItemSize % tagSize);
    fTagOffset = fVariantOffset + fMaxItemSize + ((padding == tagSize) ? 0 : padding);
 }