common: Make use of [[nodiscard]] where applicable

Now that clang-format makes [[nodiscard]] attributes format sensibly, we
can apply them to several functions within the common library to allow
the compiler to complain about any misuses of the functions.

1 files changed, 19 insertions, 18 deletions

diff --git a/src/common/multi_level_queue.h b/src/common/multi_level_queue.h
index 50acfdbf2..4b305bf40 100644
--- a/src/common/multi_level_queue.h
+++ b/src/common/multi_level_queue.h
@@ -223,15 +223,15 @@ public:
         ListShiftForward(levels[priority], n);
     }
 
-    std::size_t depth() const {
+    [[nodiscard]] std::size_t depth() const {
         return Depth;
     }
 
-    std::size_t size(u32 priority) const {
+    [[nodiscard]] std::size_t size(u32 priority) const {
         return levels[priority].size();
     }
 
-    std::size_t size() const {
+    [[nodiscard]] std::size_t size() const {
         u64 priorities = used_priorities;
         std::size_t size = 0;
         while (priorities != 0) {
@@ -242,64 +242,64 @@ public:
         return size;
     }
 
-    bool empty() const {
+    [[nodiscard]] bool empty() const {
         return used_priorities == 0;
     }
 
-    bool empty(u32 priority) const {
+    [[nodiscard]] bool empty(u32 priority) const {
         return (used_priorities & (1ULL << priority)) == 0;
     }
 
-    u32 highest_priority_set(u32 max_priority = 0) const {
+    [[nodiscard]] u32 highest_priority_set(u32 max_priority = 0) const {
         const u64 priorities =
             max_priority == 0 ? used_priorities : (used_priorities & ~((1ULL << max_priority) - 1));
         return priorities == 0 ? Depth : static_cast<u32>(CountTrailingZeroes64(priorities));
     }
 
-    u32 lowest_priority_set(u32 min_priority = Depth - 1) const {
+    [[nodiscard]] u32 lowest_priority_set(u32 min_priority = Depth - 1) const {
         const u64 priorities = min_priority >= Depth - 1
                                    ? used_priorities
                                    : (used_priorities & ((1ULL << (min_priority + 1)) - 1));
         return priorities == 0 ? Depth : 63 - CountLeadingZeroes64(priorities);
     }
 
-    const_iterator cbegin(u32 max_prio = 0) const {
+    [[nodiscard]] const_iterator cbegin(u32 max_prio = 0) const {
         const u32 priority = highest_priority_set(max_prio);
         return priority == Depth ? cend()
                                  : const_iterator{*this, levels[priority].cbegin(), priority};
     }
-    const_iterator begin(u32 max_prio = 0) const {
+    [[nodiscard]] const_iterator begin(u32 max_prio = 0) const {
         return cbegin(max_prio);
     }
-    iterator begin(u32 max_prio = 0) {
+    [[nodiscard]] iterator begin(u32 max_prio = 0) {
         const u32 priority = highest_priority_set(max_prio);
         return priority == Depth ? end() : iterator{*this, levels[priority].begin(), priority};
     }
 
-    const_iterator cend(u32 min_prio = Depth - 1) const {
+    [[nodiscard]] const_iterator cend(u32 min_prio = Depth - 1) const {
         return min_prio == Depth - 1 ? const_iterator{*this, Depth} : cbegin(min_prio + 1);
     }
-    const_iterator end(u32 min_prio = Depth - 1) const {
+    [[nodiscard]] const_iterator end(u32 min_prio = Depth - 1) const {
         return cend(min_prio);
     }
-    iterator end(u32 min_prio = Depth - 1) {
+    [[nodiscard]] iterator end(u32 min_prio = Depth - 1) {
         return min_prio == Depth - 1 ? iterator{*this, Depth} : begin(min_prio + 1);
     }
 
-    T& front(u32 max_priority = 0) {
+    [[nodiscard]] T& front(u32 max_priority = 0) {
         const u32 priority = highest_priority_set(max_priority);
         return levels[priority == Depth ? 0 : priority].front();
     }
-    const T& front(u32 max_priority = 0) const {
+    [[nodiscard]] const T& front(u32 max_priority = 0) const {
         const u32 priority = highest_priority_set(max_priority);
         return levels[priority == Depth ? 0 : priority].front();
     }
 
-    T back(u32 min_priority = Depth - 1) {
+    [[nodiscard]] T& back(u32 min_priority = Depth - 1) {
         const u32 priority = lowest_priority_set(min_priority); // intended
         return levels[priority == Depth ? 63 : priority].back();
     }
-    const T& back(u32 min_priority = Depth - 1) const {
+    [[nodiscard]] const T& back(u32 min_priority = Depth - 1) const {
         const u32 priority = lowest_priority_set(min_priority); // intended
         return levels[priority == Depth ? 63 : priority].back();
     }
@@ -329,7 +329,8 @@ private:
         in_list.splice(position, out_list, element);
     }
 
-    static const_list_iterator ListIterateTo(const std::list<T>& list, const T& element) {
+    [[nodiscard]] static const_list_iterator ListIterateTo(const std::list<T>& list,
+                                                           const T& element) {
         auto it = list.cbegin();
         while (it != list.cend() && *it != element) {
             ++it;