diff --git a/Externals/cpp-optparse/OptionParser.h b/Externals/cpp-optparse/OptionParser.h
index aab832c00c25..d9f9ff65ec24 100644
--- a/Externals/cpp-optparse/OptionParser.h
+++ b/Externals/cpp-optparse/OptionParser.h
@@ -77,7 +77,7 @@ class Values {
 class Option {
   public:
     Option(const OptionParser& p) :
-      _parser(p), _action("store"), _type("string"), _nargs(1), _callback(0) {}
+      _parser(p), _action("store"), _type("string"), _nargs(1), _callback(nullptr) {}
     virtual ~Option() {}
 
     Option& action(const std::string& a);
diff --git a/Externals/picojson/picojson.h b/Externals/picojson/picojson.h
index 8d09f05fe163..c136b11c2523 100644
--- a/Externals/picojson/picojson.h
+++ b/Externals/picojson/picojson.h
@@ -1063,7 +1063,7 @@ template <typename Iter> inline std::string parse(value &out, Iter &pos, const I
 
 template <typename Context, typename Iter> inline Iter _parse(Context &ctx, const Iter &first, const Iter &last, std::string *err) {
   input<Iter> in(first, last);
-  if (!_parse(ctx, in) && err != NULL) {
+  if (!_parse(ctx, in) && err != nullptr) {
     char buf[64];
     SNPRINTF(buf, sizeof(buf), "syntax error at line %d near: ", in.line());
     *err = buf;
diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 4a4cd61b5133..b23aeb9d3edc 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -34,7 +34,7 @@ else()
   #check_and_add_flag(SWITCH_DEFAULT -Wswitch-default)
   #check_and_add_flag(FLOAT_EQUAL -Wfloat-equal)
   #check_and_add_flag(CONVERSION -Wconversion)
-  #check_and_add_flag(ZERO_AS_NULL_POINTER_CONSTANT -Wzero-as-null-pointer-constant)
+  check_and_add_flag(ZERO_AS_NULL_POINTER_CONSTANT -Wzero-as-null-pointer-constant)
   check_and_add_flag(TYPE_LIMITS -Wtype-limits)
   check_and_add_flag(SIGN_COMPARE -Wsign-compare)
   check_and_add_flag(IGNORED_QUALIFIERS -Wignored-qualifiers)
diff --git a/Source/Core/Common/FatFsUtil.cpp b/Source/Core/Common/FatFsUtil.cpp
index f194dc22a3cc..395d6ac3eb6f 100644
--- a/Source/Core/Common/FatFsUtil.cpp
+++ b/Source/Core/Common/FatFsUtil.cpp
@@ -571,7 +571,15 @@ bool SyncSDFolderToSDImage(const std::function<bool()>& cancelled, bool determin
                   FatFsErrorToString(mount_error_code));
     return false;
   }
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
   Common::ScopeGuard unmount_guard{[] { f_unmount(""); }};
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
   if (!Pack(cancelled, root, true, tmp_buffer))
   {
@@ -795,7 +803,15 @@ bool SyncSDImageToSDFolder(const std::function<bool()>& cancelled)
                   FatFsErrorToString(mount_error_code));
     return false;
   }
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
   Common::ScopeGuard unmount_guard{[] { f_unmount(""); }};
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
   // Unpack() and GetTempFilenameForAtomicWrite() don't want the trailing separator.
   const std::string target_dir_without_slash = target_dir.substr(0, target_dir.length() - 1);
diff --git a/Source/Core/Common/GL/GLInterface/GLX.cpp b/Source/Core/Common/GL/GLInterface/GLX.cpp
index b04296d0968f..ce16bb21553b 100644
--- a/Source/Core/Common/GL/GLInterface/GLX.cpp
+++ b/Source/Core/Common/GL/GLInterface/GLX.cpp
@@ -155,7 +155,8 @@ bool GLContextGLX::Initialize(const WindowSystemInfo& wsi, bool stereo, bool cor
            GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB, None}};
 
       s_glxError = false;
-      m_context = glXCreateContextAttribs(m_display, m_fbconfig, 0, True, &context_attribs[0]);
+      m_context =
+          glXCreateContextAttribs(m_display, m_fbconfig, nullptr, True, &context_attribs[0]);
       XSync(m_display, False);
       if (!m_context || s_glxError)
         continue;
@@ -174,7 +175,8 @@ bool GLContextGLX::Initialize(const WindowSystemInfo& wsi, bool stereo, bool cor
     std::array<int, 5> context_attribs_legacy = {
         {GLX_CONTEXT_MAJOR_VERSION_ARB, 1, GLX_CONTEXT_MINOR_VERSION_ARB, 0, None}};
     s_glxError = false;
-    m_context = glXCreateContextAttribs(m_display, m_fbconfig, 0, True, &context_attribs_legacy[0]);
+    m_context =
+        glXCreateContextAttribs(m_display, m_fbconfig, nullptr, True, &context_attribs_legacy[0]);
     XSync(m_display, False);
     m_attribs.clear();
     m_attribs.insert(m_attribs.end(), context_attribs_legacy.begin(), context_attribs_legacy.end());
diff --git a/Source/Core/Core/IOS/Network/KD/VFF/VFFUtil.cpp b/Source/Core/Core/IOS/Network/KD/VFF/VFFUtil.cpp
index 16ba1b1ad78a..f8e87c0bfac9 100644
--- a/Source/Core/Core/IOS/Network/KD/VFF/VFFUtil.cpp
+++ b/Source/Core/Core/IOS/Network/KD/VFF/VFFUtil.cpp
@@ -294,7 +294,14 @@ ErrorCode OpenVFF(const std::string& path, const std::string& filename,
       return;
     }
 
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
     Common::ScopeGuard unmount_guard{[] { f_unmount(""); }};
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
     const auto write_error_code = WriteFile(filename, data);
     if (write_error_code != WC24_OK)
diff --git a/Source/Core/Core/IOS/USB/Bluetooth/BTReal.cpp b/Source/Core/Core/IOS/USB/Bluetooth/BTReal.cpp
index 72f591c7f576..2edb6bf0c41d 100644
--- a/Source/Core/Core/IOS/USB/Bluetooth/BTReal.cpp
+++ b/Source/Core/Core/IOS/USB/Bluetooth/BTReal.cpp
@@ -16,7 +16,14 @@
 #include <vector>
 
 #include <fmt/format.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
 #include "Common/ChunkFile.h"
 #include "Common/Logging/Log.h"
diff --git a/Source/Core/Core/IOS/USB/Host.cpp b/Source/Core/Core/IOS/USB/Host.cpp
index 8870f730b058..5f4d3208efc3 100644
--- a/Source/Core/Core/IOS/USB/Host.cpp
+++ b/Source/Core/Core/IOS/USB/Host.cpp
@@ -11,7 +11,14 @@
 #include <utility>
 
 #ifdef __LIBUSB__
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 #endif
 
 #include "Common/Assert.h"
diff --git a/Source/Core/Core/IOS/USB/LibusbDevice.cpp b/Source/Core/Core/IOS/USB/LibusbDevice.cpp
index 9e305b917981..0b01c0ddd372 100644
--- a/Source/Core/Core/IOS/USB/LibusbDevice.cpp
+++ b/Source/Core/Core/IOS/USB/LibusbDevice.cpp
@@ -13,7 +13,14 @@
 #include <utility>
 #include <vector>
 
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
 #include "Common/Assert.h"
 #include "Common/Logging/Log.h"
diff --git a/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp b/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
index 62e8ec2987ca..4d147b1d3baf 100644
--- a/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
+++ b/Source/Core/Core/IOS/USB/USB_HID/HIDv4.cpp
@@ -103,7 +103,7 @@ std::optional<IPCReply> USB_HIDv4::GetDeviceChange(const IOCtlRequest& request)
 IPCReply USB_HIDv4::Shutdown(const IOCtlRequest& request)
 {
   std::lock_guard lk{m_devicechange_hook_address_mutex};
-  if (m_devicechange_hook_request != 0)
+  if (m_devicechange_hook_request)
   {
     auto& system = Core::System::GetInstance();
     auto& memory = system.GetMemory();
diff --git a/Source/Core/Core/LibusbUtils.cpp b/Source/Core/Core/LibusbUtils.cpp
index 1b1852dddd11..7eb628b09b88 100644
--- a/Source/Core/Core/LibusbUtils.cpp
+++ b/Source/Core/Core/LibusbUtils.cpp
@@ -7,7 +7,14 @@
 #include <thread>
 
 #if defined(__LIBUSB__)
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 #endif
 
 #include "Common/Assert.h"
diff --git a/Source/Core/Core/PowerPC/Expression.cpp b/Source/Core/Core/PowerPC/Expression.cpp
index 597c77c98550..ffa9bc96ae75 100644
--- a/Source/Core/Core/PowerPC/Expression.cpp
+++ b/Source/Core/Core/PowerPC/Expression.cpp
@@ -11,7 +11,14 @@
 #include <string_view>
 #include <utility>
 
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <expr.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 
 #include "Common/BitUtils.h"
 #include "Common/CommonTypes.h"
diff --git a/Source/Core/Core/PowerPC/GDBStub.cpp b/Source/Core/Core/PowerPC/GDBStub.cpp
index 94d3e2e0608b..4356fdad98e2 100644
--- a/Source/Core/Core/PowerPC/GDBStub.cpp
+++ b/Source/Core/Core/PowerPC/GDBStub.cpp
@@ -1048,7 +1048,7 @@ void InitLocal(const char* socket)
   addr.sun_family = AF_UNIX;
   strcpy(addr.sun_path, socket);
 
-  InitGeneric(PF_LOCAL, (const sockaddr*)&addr, sizeof(addr), NULL, NULL);
+  InitGeneric(PF_LOCAL, (const sockaddr*)&addr, sizeof(addr), nullptr, nullptr);
 }
 #endif
 
diff --git a/Source/Core/DolphinQt/QtUtils/FlowLayout.cpp b/Source/Core/DolphinQt/QtUtils/FlowLayout.cpp
index 5ef3e0aa08fe..b2c4eb75d59d 100644
--- a/Source/Core/DolphinQt/QtUtils/FlowLayout.cpp
+++ b/Source/Core/DolphinQt/QtUtils/FlowLayout.cpp
@@ -75,7 +75,7 @@ QLayoutItem* FlowLayout::takeAt(int index)
   if (index >= 0 && index < m_item_list.size())
     return m_item_list.takeAt(index);
   else
-    return 0;
+    return nullptr;
 }
 
 Qt::Orientations FlowLayout::expandingDirections() const
@@ -167,7 +167,7 @@ int FlowLayout::smartSpacing(QStyle::PixelMetric pm) const
   else if (parent->isWidgetType())
   {
     QWidget* pw = static_cast<QWidget*>(parent);
-    return pw->style()->pixelMetric(pm, 0, pw);
+    return pw->style()->pixelMetric(pm, nullptr, pw);
   }
   else
   {
diff --git a/Source/Core/DolphinQt/Settings/GameCubePane.cpp b/Source/Core/DolphinQt/Settings/GameCubePane.cpp
index 55510fd9f94f..a19fce31fbae 100644
--- a/Source/Core/DolphinQt/Settings/GameCubePane.cpp
+++ b/Source/Core/DolphinQt/Settings/GameCubePane.cpp
@@ -410,7 +410,7 @@ void GameCubePane::BrowseMemcard(ExpansionInterface::Slot slot)
   const QString filename = DolphinFileDialog::getSaveFileName(
       this, tr("Choose a file to open or create"),
       QString::fromStdString(File::GetUserPath(D_GCUSER_IDX)),
-      tr("GameCube Memory Cards (*.raw *.gcp)"), 0, QFileDialog::DontConfirmOverwrite);
+      tr("GameCube Memory Cards (*.raw *.gcp)"), nullptr, QFileDialog::DontConfirmOverwrite);
 
   if (!filename.isEmpty())
     SetMemcard(slot, filename);
@@ -618,7 +618,7 @@ void GameCubePane::BrowseAGPRom(ExpansionInterface::Slot slot)
 
   QString filename = DolphinFileDialog::getSaveFileName(
       this, tr("Choose a file to open"), QString::fromStdString(File::GetUserPath(D_GCUSER_IDX)),
-      tr("Game Boy Advance Carts (*.gba)"), 0, QFileDialog::DontConfirmOverwrite);
+      tr("Game Boy Advance Carts (*.gba)"), nullptr, QFileDialog::DontConfirmOverwrite);
 
   if (!filename.isEmpty())
     SetAGPRom(slot, filename);
diff --git a/Source/Core/DolphinQt/ToolBar.cpp b/Source/Core/DolphinQt/ToolBar.cpp
index 49f384848d72..b50e48bf9eac 100644
--- a/Source/Core/DolphinQt/ToolBar.cpp
+++ b/Source/Core/DolphinQt/ToolBar.cpp
@@ -154,14 +154,14 @@ void ToolBar::UpdatePausePlayButtonState(const bool playing_state)
 {
   if (playing_state)
   {
-    disconnect(m_pause_play_action, 0, 0, 0);
+    disconnect(m_pause_play_action, nullptr, nullptr, nullptr);
     m_pause_play_action->setText(tr("Pause"));
     m_pause_play_action->setIcon(Resources::GetScaledThemeIcon("pause"));
     connect(m_pause_play_action, &QAction::triggered, this, &ToolBar::PausePressed);
   }
   else
   {
-    disconnect(m_pause_play_action, 0, 0, 0);
+    disconnect(m_pause_play_action, nullptr, nullptr, nullptr);
     m_pause_play_action->setText(tr("Play"));
     m_pause_play_action->setIcon(Resources::GetScaledThemeIcon("play"));
     connect(m_pause_play_action, &QAction::triggered, this, &ToolBar::PlayPressed);
diff --git a/Source/Core/InputCommon/GCAdapter.cpp b/Source/Core/InputCommon/GCAdapter.cpp
index a3853e9e6cf3..7780d486dd3c 100644
--- a/Source/Core/InputCommon/GCAdapter.cpp
+++ b/Source/Core/InputCommon/GCAdapter.cpp
@@ -17,7 +17,14 @@
 #include <optional>
 
 #if GCADAPTER_USE_LIBUSB_IMPLEMENTATION
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 #elif GCADAPTER_USE_ANDROID_IMPLEMENTATION
 #include <jni.h>
 #endif
diff --git a/Source/Core/UICommon/Disassembler.cpp b/Source/Core/UICommon/Disassembler.cpp
index 62e4d32c6d26..15555dc0b9ef 100644
--- a/Source/Core/UICommon/Disassembler.cpp
+++ b/Source/Core/UICommon/Disassembler.cpp
@@ -46,7 +46,7 @@ HostDisassemblerLLVM::HostDisassemblerLLVM(const std::string& host_disasm, int i
   LLVMInitializeAllTargetMCs();
   LLVMInitializeAllDisassemblers();
 
-  m_llvm_context = LLVMCreateDisasmCPU(host_disasm.c_str(), cpu.c_str(), nullptr, 0, 0, nullptr);
+  m_llvm_context = LLVMCreateDisasmCPU(host_disasm.c_str(), cpu.c_str(), nullptr, 0, nullptr, nullptr);
 
   // Couldn't create llvm context
   if (!m_llvm_context)
diff --git a/Source/Core/UICommon/ResourcePack/ResourcePack.cpp b/Source/Core/UICommon/ResourcePack/ResourcePack.cpp
index 355dc8acf2b5..7f670e774828 100644
--- a/Source/Core/UICommon/ResourcePack/ResourcePack.cpp
+++ b/Source/Core/UICommon/ResourcePack/ResourcePack.cpp
@@ -36,7 +36,7 @@ ResourcePack::ResourcePack(const std::string& path) : m_path(path)
     return;
   }
 
-  if (unzLocateFile(file, "manifest.json", 0) == UNZ_END_OF_LIST_OF_FILE)
+  if (unzLocateFile(file, "manifest.json", nullptr) == UNZ_END_OF_LIST_OF_FILE)
   {
     m_valid = false;
     m_error = "Resource pack is missing a manifest.";
@@ -63,7 +63,7 @@ ResourcePack::ResourcePack(const std::string& path) : m_path(path)
     return;
   }
 
-  if (unzLocateFile(file, "logo.png", 0) != UNZ_END_OF_LIST_OF_FILE)
+  if (unzLocateFile(file, "logo.png", nullptr) != UNZ_END_OF_LIST_OF_FILE)
   {
     unz_file_info64 logo_info{};
     unzGetCurrentFileInfo64(file, &logo_info, nullptr, 0, nullptr, 0, nullptr, 0);
diff --git a/Source/Core/UICommon/USBUtils.cpp b/Source/Core/UICommon/USBUtils.cpp
index 2264afe82cca..f86dbb7169ba 100644
--- a/Source/Core/UICommon/USBUtils.cpp
+++ b/Source/Core/UICommon/USBUtils.cpp
@@ -7,7 +7,14 @@
 
 #include <fmt/format.h>
 #ifdef __LIBUSB__
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
+#endif
 #include <libusb.h>
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
 #endif
 
 #include "Common/CommonTypes.h"
diff --git a/Source/Core/VideoBackends/OGL/OGLTexture.cpp b/Source/Core/VideoBackends/OGL/OGLTexture.cpp
index ad0e32bb390e..4e90211c59f3 100644
--- a/Source/Core/VideoBackends/OGL/OGLTexture.cpp
+++ b/Source/Core/VideoBackends/OGL/OGLTexture.cpp
@@ -296,7 +296,7 @@ OGLStagingTexture::OGLStagingTexture(StagingTextureType type, const TextureConfi
 
 OGLStagingTexture::~OGLStagingTexture()
 {
-  if (m_fence != 0)
+  if (m_fence != nullptr)
     glDeleteSync(m_fence);
   if (m_map_pointer)
   {
@@ -418,7 +418,7 @@ void OGLStagingTexture::CopyFromTexture(const AbstractTexture* src,
   // If we support buffer storage, create a fence for synchronization.
   if (UsePersistentStagingBuffers())
   {
-    if (m_fence != 0)
+    if (m_fence != nullptr)
       glDeleteSync(m_fence);
 
     glMemoryBarrier(GL_CLIENT_MAPPED_BUFFER_BARRIER_BIT);
@@ -479,7 +479,7 @@ void OGLStagingTexture::CopyToTexture(const MathUtil::Rectangle<int>& src_rect,
   // If we support buffer storage, create a fence for synchronization.
   if (UsePersistentStagingBuffers())
   {
-    if (m_fence != 0)
+    if (m_fence != nullptr)
       glDeleteSync(m_fence);
 
     m_fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
@@ -493,7 +493,7 @@ void OGLStagingTexture::Flush()
 {
   // No-op when not using buffer storage, as the transfers happen on Map().
   // m_fence will always be zero in this case.
-  if (m_fence == 0)
+  if (m_fence == nullptr)
   {
     m_needs_flush = false;
     return;
@@ -501,7 +501,7 @@ void OGLStagingTexture::Flush()
 
   glClientWaitSync(m_fence, 0, GL_TIMEOUT_IGNORED);
   glDeleteSync(m_fence);
-  m_fence = 0;
+  m_fence = nullptr;
   m_needs_flush = false;
 }
 
diff --git a/Source/Core/VideoBackends/OGL/OGLTexture.h b/Source/Core/VideoBackends/OGL/OGLTexture.h
index 9d1c11950597..f80aa98725a8 100644
--- a/Source/Core/VideoBackends/OGL/OGLTexture.h
+++ b/Source/Core/VideoBackends/OGL/OGLTexture.h
@@ -75,7 +75,7 @@ class OGLStagingTexture final : public AbstractStagingTexture
   GLenum m_target;
   GLuint m_buffer_name;
   size_t m_buffer_size;
-  GLsync m_fence = 0;
+  GLsync m_fence = nullptr;
 };
 
 class OGLFramebuffer final : public AbstractFramebuffer