Everywhere: Use default StringView constructor over nullptr

While null StringViews are just as bad, these prevent the removal of
StringView(char const*) as that constructor accepts a nullptr.

No functional changes.

Kernel/Interrupts/APIC.cpp

@@ -81,7 +81,7 @@ public:
 
     virtual HandlerType type() const override { return HandlerType::IRQHandler; }
     virtual StringView purpose() const override { return "IPI Handler"sv; }
-    virtual StringView controller() const override { return nullptr; }
+    virtual StringView controller() const override { return {}; }
 
     virtual size_t sharing_devices_count() const override { return 0; }
     virtual bool is_shared_handler() const override { return false; }
@@ -112,7 +112,7 @@ public:
 
     virtual HandlerType type() const override { return HandlerType::IRQHandler; }
     virtual StringView purpose() const override { return "SMP Error Handler"sv; }
-    virtual StringView controller() const override { return nullptr; }
+    virtual StringView controller() const override { return {}; }
 
     virtual size_t sharing_devices_count() const override { return 0; }
     virtual bool is_shared_handler() const override { return false; }

Kernel/PerformanceEventBuffer.cpp

@@ -348,7 +348,7 @@ ErrorOr<void> PerformanceEventBuffer::add_process(Process const& process, Proces
     ErrorOr<void> result;
     process.for_each_thread([&](auto& thread) {
         result = append_with_ip_and_bp(process.pid(), thread.tid().value(),
-            0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, 0, nullptr);
+            0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, 0, {});
         return result.is_error() ? IterationDecision::Break : IterationDecision::Continue;
     });
     TRY(result);

Kernel/PerformanceManager.h

@@ -34,7 +34,7 @@ public:
         if (g_profiling_all_threads) {
             VERIFY(g_global_perf_events);
             [[maybe_unused]] auto rc = g_global_perf_events->append_with_ip_and_bp(
-                process.pid(), 0, 0, 0, PERF_EVENT_PROCESS_EXIT, 0, 0, 0, nullptr);
+                process.pid(), 0, 0, 0, PERF_EVENT_PROCESS_EXIT, 0, 0, 0, {});
         }
     }
 
@@ -43,7 +43,7 @@ public:
         if (thread.is_profiling_suppressed())
             return;
         if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
-            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_CREATE, thread.tid().value(), 0, nullptr, &thread);
+            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_CREATE, thread.tid().value(), 0, {}, &thread);
         }
     }
 
@@ -52,7 +52,7 @@ public:
         // As an exception this doesn't check whether profiling is suppressed for
         // the thread so we can record the thread_exit event anyway.
         if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
-            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_EXIT, thread.tid().value(), 0, nullptr, &thread);
+            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_EXIT, thread.tid().value(), 0, {}, &thread);
         }
     }
 
@@ -62,7 +62,7 @@ public:
             return;
         if (auto* event_buffer = current_thread.process().current_perf_events_buffer()) {
             [[maybe_unused]] auto rc = event_buffer->append_with_ip_and_bp(
-                current_thread.pid(), current_thread.tid(), regs, PERF_EVENT_SAMPLE, lost_time, 0, 0, nullptr);
+                current_thread.pid(), current_thread.tid(), regs, PERF_EVENT_SAMPLE, lost_time, 0, 0, {});
         }
     }
 
@@ -76,7 +76,7 @@ public:
     inline static void add_unmap_perf_event(Process& current_process, Memory::VirtualRange const& region)
     {
         if (auto* event_buffer = current_process.current_perf_events_buffer()) {
-            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MUNMAP, region.base().get(), region.size(), nullptr);
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MUNMAP, region.base().get(), region.size(), {});
         }
     }
 
@@ -85,7 +85,7 @@ public:
         if (current_thread.is_profiling_suppressed())
             return;
         if (auto* event_buffer = current_thread.process().current_perf_events_buffer()) {
-            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_CONTEXT_SWITCH, next_thread.pid().value(), next_thread.tid().value(), nullptr);
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_CONTEXT_SWITCH, next_thread.pid().value(), next_thread.tid().value(), {});
         }
     }
 
@@ -94,7 +94,7 @@ public:
         if (current_thread.is_profiling_suppressed())
             return;
         if (auto* event_buffer = current_thread.process().current_perf_events_buffer()) {
-            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_KMALLOC, size, ptr, nullptr);
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_KMALLOC, size, ptr, {});
         }
     }
 
@@ -103,7 +103,7 @@ public:
         if (current_thread.is_profiling_suppressed())
             return;
         if (auto* event_buffer = current_thread.process().current_perf_events_buffer()) {
-            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_KFREE, size, ptr, nullptr);
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_KFREE, size, ptr, {});
         }
     }
 
@@ -113,7 +113,7 @@ public:
             return;
         if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
             [[maybe_unused]] auto rc = event_buffer->append_with_ip_and_bp(
-                thread.pid(), thread.tid(), regs, PERF_EVENT_PAGE_FAULT, 0, 0, 0, nullptr);
+                thread.pid(), thread.tid(), regs, PERF_EVENT_PAGE_FAULT, 0, 0, 0, {});
         }
     }
 
@@ -123,7 +123,7 @@ public:
             return;
         if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
             [[maybe_unused]] auto rc = event_buffer->append_with_ip_and_bp(
-                thread.pid(), thread.tid(), regs, PERF_EVENT_SYSCALL, 0, 0, 0, nullptr);
+                thread.pid(), thread.tid(), regs, PERF_EVENT_SYSCALL, 0, 0, 0, {});
         }
     }
 
@@ -158,7 +158,7 @@ public:
             filepath_string_index = registered_result.value();
         }
 
-        [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_READ, fd, size, 0, &thread, filepath_string_index, start_timestamp, result); // wrong arguments
+        [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_READ, fd, size, {}, &thread, filepath_string_index, start_timestamp, result); // wrong arguments
     }
 
     inline static void timer_tick(RegisterState const& regs)

Kernel/Syscalls/perf_event.cpp

@@ -15,7 +15,7 @@ ErrorOr<FlatPtr> Process::sys$perf_event(int type, FlatPtr arg1, FlatPtr arg2)
     auto* events_buffer = current_perf_events_buffer();
     if (!events_buffer)
         return 0;
-    TRY(events_buffer->append(type, arg1, arg2, nullptr));
+    TRY(events_buffer->append(type, arg1, arg2, {}));
     return 0;
 }
 

Kernel/Time/HardwareTimer.h

@@ -133,7 +133,7 @@ public:
     virtual bool is_shared_handler() const override { return false; }
     virtual bool is_sharing_with_others() const override { return false; }
     virtual HandlerType type() const override { return HandlerType::IRQHandler; }
-    virtual StringView controller() const override { return nullptr; }
+    virtual StringView controller() const override { return {}; }
     virtual bool eoi() override;
 
     virtual u32 frequency() const override { return (u32)m_frequency; }