From a9b72fd53529a679f0ab2dd01eadc70e009ab2d1 Mon Sep 17 00:00:00 2001
From: Philippe Canal <pcanal@fnal.gov>
Date: Thu, 21 Nov 2024 21:48:09 -0600
Subject: [PATCH] io: Workaround TDataType legacy type for enums (part2)

---
 io/io/src/TStreamerInfo.cxx | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/io/io/src/TStreamerInfo.cxx b/io/io/src/TStreamerInfo.cxx
index 779118cdd37da..098809d6666fc 100644
--- a/io/io/src/TStreamerInfo.cxx
+++ b/io/io/src/TStreamerInfo.cxx
@@ -532,6 +532,7 @@ void TStreamerInfo::Build(Bool_t isTransient)
             if (auto enumdesc = TEnum::GetEnum(dm->GetFullTypeName(), TEnum::kNone))
             {
                // NOTE: We might simplify this by having the dm->fDataType being 'correct'.
+               // If we do we need to also make sure to update the old type accordingly
                element->SetNewType(enumdesc->GetUnderlyingType());
                element->SetType(TStreamerInfo::kInt);
             }
@@ -2186,6 +2187,13 @@ void TStreamerInfo::BuildOld()
                // All the values of EDataType have the same semantic in EReadWrite
                newType = (EReadWrite)theType->GetType();
             }
+            if (dm->IsEnum()) {
+               if (auto enumdesc = TEnum::GetEnum(dm->GetFullTypeName(), TEnum::kNone))
+               {
+                  // NOTE: We might simplify this by having the dm->fDataType being 'correct'.
+                  newType = enumdesc->GetUnderlyingType();
+               }
+            }
             if ((newType == ::kChar_t) && dmIsPtr && !isArray && !hasCount) {
                newType = ::kCharStar;
             } else if (dmIsPtr) {