From 28ce8d91f69a71d25f5e4a23da9fbbdd5aac30eb Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Fri, 5 Jan 2024 10:37:04 +0100
Subject: [PATCH] Avoid passing immutable objects to Objectify (#5557)

Immutable objects should never be able to turn into mutable objects.
Strictly speaking this is violated when passing an immutable list or
record to Objectify. Unfortunately we can't currently reject such inputs
because some GAP library code relies on this misfeature (and possibly
also in some packages). But we can at least reduce the occurrences for
now to prepare for a potential stricter future.

This is part of my long-term goal to minimize "magic" changes to GAP
types, which is an incredibly dangerous feature. It also makes correct
and sage bridging to other language more difficult: foreign language
wrapper objects around GAP objects always have to worry about the GAP
object magically changing. It also was always an issue for HPC-GAP.
Thus I hope that one day we can restrict this to a minimal and fully
enumerable set of possible conversions.
---
 lib/rvecempt.gi | 2 +-
 lib/rwsgrp.gi   | 6 ++----
 lib/streams.gi  | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/lib/rvecempt.gi b/lib/rvecempt.gi
index a74422bf69..5b0263af3e 100644
--- a/lib/rvecempt.gi
+++ b/lib/rvecempt.gi
@@ -32,7 +32,7 @@ InstallMethod( EmptyRowVector,
                                    IsRowVector
                                and IsEmpty
                                and IsEmptyRowVectorRep ),
-                      MakeImmutable([]) );
+                      [] );
     end );
 
 
diff --git a/lib/rwsgrp.gi b/lib/rwsgrp.gi
index e8428cb437..10f543453e 100644
--- a/lib/rwsgrp.gi
+++ b/lib/rwsgrp.gi
@@ -23,8 +23,7 @@ InstallMethod( ElementByRws,
     0,
 
 function( fam, elm )
-    elm := Immutable([ elm ]);
-    return Objectify( fam!.defaultType, elm );
+    return Objectify( fam!.defaultType, [ elm ] );
 end );
 
 ##
@@ -43,8 +42,7 @@ function( fam, list )
 
     freefam := UnderlyingFamily( fam!.rewritingSystem );
     elm := ObjByExtRep( freefam, list );
-    elm := Immutable([ elm ]);
-    return Objectify( fam!.defaultType, elm );
+    return Objectify( fam!.defaultType, [ elm ] );
 end );
 
 
diff --git a/lib/streams.gi b/lib/streams.gi
index cbd7059fad..df426f85b2 100644
--- a/lib/streams.gi
+++ b/lib/streams.gi
@@ -1380,7 +1380,7 @@ InstallGlobalFunction( InputOutputLocalProcess,
     od;
     basename := exec{[i+1..Length(exec)]};
     return Objectify(InputOutputStreamByPtyDefaultType,
-                   Immutable([ptynum, basename, argts, false]) );
+                   [ptynum, Immutable(basename), Immutable(argts), false] );
 end);
 
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