[Bf-blender-cvs] [a54c1f1e771] blender-v2.83-release: Fix T76155: 'Object lost data' on copy-pasting with new undo code.

[Bastien Montagne]

Commit: a54c1f1e77147352dfab1233ef63307e87e9f09c
Author: Bastien Montagne
Date:   Wed Apr 29 18:11:33 2020 +0200
Branches: blender-v2.83-release
https://developer.blender.org/rBa54c1f1e77147352dfab1233ef63307e87e9f09c

Fix T76155: 'Object lost data' on copy-pasting with new undo code.

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M	source/blender/blenloader/intern/readfile.c

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diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 8837dccb837..98e6369b634 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -9659,7 +9659,9 @@ static bool read_libblock_undo_restore(
     /* Do not add LIB_TAG_NEW here, this should not be needed/used in undo case anyway (as
      * this is only for do_version-like code), but for sake of consistency, and also because
      * it will tell us which ID is re-used from old Main, and which one is actually new. */
-    const int id_tag = tag | LIB_TAG_NEED_LINK | LIB_TAG_UNDO_OLD_ID_REUSED;
+    /* Also do not add LIB_TAG_NEED_LINK, those IDs will never be re-liblinked, hence that tag will
+     * never be cleared, leading to critical issue in link/appemd code. */
+    const int id_tag = tag | LIB_TAG_UNDO_OLD_ID_REUSED;
     read_libblock_undo_restore_identical(fd, main, id, id_old, id_tag);
 
     /* Insert into library map for lookup by newly read datablocks (with pointer value bhead->old).