remove const correctness violations

This is possibly related to a livelock where several threads do const
removal in their respective code paths.

Use the `mutable' specifier for the mutexes and spline's cached data.

Now using the `mutable' specifier, get rid of <optional> in
compat/mutex.

1 files changed, 5 insertions, 9 deletions

diff --git a/compat/copyable-mutex.hpp b/compat/copyable-mutex.hpp
index 46c6c88c..37e6802b 100644
--- a/compat/copyable-mutex.hpp
+++ b/compat/copyable-mutex.hpp
@@ -1,25 +1,21 @@
 #pragma once
 
-#include <optional>
-
 #include <QMutex>
 
 #include "export.hpp"
 
 class OTR_COMPAT_EXPORT mutex
 {
-    std::optional<QMutex> inner;
+    mutable QMutex inner;
 
 public:
-    enum mode
-    {
-        recursive = QMutex::Recursive,
-        normal = QMutex::NonRecursive,
-    };
+    using RecursionMode = QMutex::RecursionMode;
+    static constexpr inline RecursionMode Recursive = RecursionMode::Recursive;
+    static constexpr inline RecursionMode NonRecursive = RecursionMode::NonRecursive;
 
     mutex& operator=(const mutex& datum);
     mutex(const mutex& datum);
-    explicit mutex(mode m = normal);
+    explicit mutex(RecursionMode m);
 
     QMutex* operator&() const;
     operator QMutex*() const;