From d8330abbf06b0be5b45bd99f9c7e8fbb9486f025 Mon Sep 17 00:00:00 2001
From: ferdymercury <ferdymercury@users.noreply.github.com>
Date: Tue, 26 Mar 2024 15:18:05 +0100
Subject: [PATCH] [hadd] avoid large RAM in hadd with multiple subdirs

Fixes https://github.com/root-project/root/issues/13531
---
 io/io/src/TFileMerger.cxx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/io/io/src/TFileMerger.cxx b/io/io/src/TFileMerger.cxx
index e49daac3f5908..2972643b7d705 100644
--- a/io/io/src/TFileMerger.cxx
+++ b/io/io/src/TFileMerger.cxx
@@ -580,6 +580,8 @@ Bool_t TFileMerger::MergeOne(TDirectory *target, TList *sourcelist, Int_t type,
       // If this folder is a onlyListed object, merge everything inside.
       if (onlyListed) type &= ~kOnlyListed;
       status = MergeRecursive(newdir, sourcelist, type);
+      // Delete newdir directory after having written it (merged)
+      if (!(type&kIncremental)) delete newdir;
       if (onlyListed) type |= kOnlyListed;
       if (!status) return kFALSE;
    } else if (!cl->IsTObject() && cl->GetMerge()) {