settings: Fix MSVC issues

According to https://stackoverflow.com/questions/469508, we run into a
MSVC bug (since VS 2005) when using diamond inheritance for
RangedSetting.

This explicitly implements those functions in RangedSetting. GetValue is
implemented as just calling the inherited version. The explicit
converson operator is reimplemented. I opted for this over ignoring the
warning with a pragma since this specifies the inherited behavior, and I
have now less faith in MSVC to pick the right one.

In addition, we mark destructors as virtual to silence what I believe is
a fair MSVC compilation error.

1 files changed, 22 insertions, 7 deletions

diff --git a/src/common/settings.h b/src/common/settings.h
index c4afff50b..1ba9b606c 100644
--- a/src/common/settings.h
+++ b/src/common/settings.h
@@ -75,7 +75,7 @@ public:
      */
     explicit BasicSetting(const Type& default_val, const std::string& name)
         : default_value{default_val}, global{default_val}, label{name} {}
-    ~BasicSetting() = default;
+    virtual ~BasicSetting() = default;
 
     /**
      *  Returns a reference to the setting's value.
@@ -161,7 +161,7 @@ public:
     explicit BasicRangedSetting(const Type& default_val, const Type& min_val, const Type& max_val,
                                 const std::string& name)
         : BasicSetting<Type>{default_val, name}, minimum{min_val}, maximum{max_val} {}
-    ~BasicRangedSetting() = default;
+    virtual ~BasicRangedSetting() = default;
 
     /**
      * Like BasicSetting's SetValue, except value is clamped to the range of the setting.
@@ -208,7 +208,7 @@ public:
      */
     explicit Setting(const Type& default_val, const std::string& name)
         : BasicSetting<Type>(default_val, name) {}
-    ~Setting() = default;
+    virtual ~Setting() = default;
 
     /**
      * Tells this setting to represent either the global or custom setting when other member
@@ -237,13 +237,13 @@ public:
      *
      * @returns The required value of the setting
      */
-    [[nodiscard]] const Type& GetValue() const override {
+    [[nodiscard]] virtual const Type& GetValue() const override {
         if (use_global) {
             return this->global;
         }
         return custom;
     }
-    [[nodiscard]] const Type& GetValue(bool need_global) const {
+    [[nodiscard]] virtual const Type& GetValue(bool need_global) const {
         if (use_global || need_global) {
             return this->global;
         }
@@ -286,7 +286,7 @@ public:
      *
      * @returns A reference to the current setting value
      */
-    explicit operator const Type&() const override {
+    virtual explicit operator const Type&() const override {
         if (use_global) {
             return this->global;
         }
@@ -318,7 +318,22 @@ public:
         : BasicSetting<Type>{default_val, name},
           BasicRangedSetting<Type>{default_val, min_val, max_val, name}, Setting<Type>{default_val,
                                                                                        name} {}
-    ~RangedSetting() = default;
+    virtual ~RangedSetting() = default;
+
+    // The following are needed to avoid a MSVC bug
+    // (source: https://stackoverflow.com/questions/469508)
+    [[nodiscard]] const Type& GetValue() const override {
+        return Setting<Type>::GetValue();
+    }
+    [[nodiscard]] const Type& GetValue(bool need_global) const override {
+        return Setting<Type>::GetValue(need_global);
+    }
+    explicit operator const Type&() const override {
+        if (this->use_global) {
+            return this->global;
+        }
+        return this->custom;
+    }
 
     /**
      * Like BasicSetting's SetValue, except value is clamped to the range of the setting. Sets the