From 51d36dfd076a98cd761ab312ab10792725ed7a29 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Mon, 20 Jul 2026 12:23:51 +0100
Subject: [PATCH] qt: Fix `-Wsfinae-incomplete` warnings when building with GCC
 16.x

According to the CMake documentation for `AUTOMOC`, all `moc` output
files that are not included in a source file are aggregated into the
CMake-generated `<AUTOGEN_BUILD_DIR>/mocs_compilation.cpp`, which is
added to the target's sources.

Within that single translation unit, `moc`-generated code checks the
completeness of a signal or slot parameter type while it is still only
forward-declared, and the type is completed later, when a subsequently
included `moc_*.cpp` file pulls in the header that defines it. GCC 16.x
diagnoses this pattern with the `-Wsfinae-incomplete` warning, which is
enabled by default.

Including the `moc` output files at the end of the corresponding source
files excludes them from `mocs_compilation.cpp`, so each one is
compiled in a translation unit where the relevant types are complete.

Additionally:
1. Some of the `BitcoinGUI` class's private members are gated with
   `#ifdef ENABLE_WALLET` to prevent `-Wunused-private-field` warnings
   when building with `-DENABLE_WALLET=OFF`.
2. `test/lint/lint-includes.py` is adjusted to allow new `#include`
   statements.
---
 src/qt/bitcoingui.cpp         | 2 ++
 src/qt/bitcoingui.h           | 8 ++++++--
 src/qt/qvalidatedlineedit.cpp | 2 ++
 src/qt/sendcoinsentry.cpp     | 2 ++
 test/lint/lint-includes.py    | 6 +++++-
 5 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 9d3f7ad639f..5f169a951c4 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -1721,3 +1721,5 @@ void UnitDisplayStatusBarControl::onMenuSelection(QAction* action)
         optionsModel->setDisplayUnit(action->data());
     }
 }
+
+#include <moc_bitcoingui.cpp>
diff --git a/src/qt/bitcoingui.h b/src/qt/bitcoingui.h
index 2322860a710..babb8961622 100644
--- a/src/qt/bitcoingui.h
+++ b/src/qt/bitcoingui.h
@@ -114,7 +114,9 @@ protected:
 
 private:
     interfaces::Node& m_node;
+#ifdef ENABLE_WALLET
     WalletController* m_wallet_controller{nullptr};
+#endif // ENABLE_WALLET
     std::unique_ptr<interfaces::Handler> m_handler_message_box;
     std::unique_ptr<interfaces::Handler> m_handler_question;
     ClientModel* clientModel = nullptr;
@@ -158,15 +160,17 @@ private:
     QAction* m_restore_wallet_action{nullptr};
     QAction* m_close_wallet_action{nullptr};
     QAction* m_close_all_wallets_action{nullptr};
+#ifdef ENABLE_WALLET
     QAction* m_wallet_selector_label_action = nullptr;
     QAction* m_wallet_selector_action = nullptr;
+#endif // ENABLE_WALLET
     QAction* m_mask_values_action{nullptr};
     QAction* m_migrate_wallet_action{nullptr};
     QMenu* m_migrate_wallet_menu{nullptr};
-
+#ifdef ENABLE_WALLET
     QLabel *m_wallet_selector_label = nullptr;
     QComboBox* m_wallet_selector = nullptr;
-
+#endif // ENABLE_WALLET
     QSystemTrayIcon* trayIcon = nullptr;
     const std::unique_ptr<QMenu> trayIconMenu;
     Notificator* notificator = nullptr;
diff --git a/src/qt/qvalidatedlineedit.cpp b/src/qt/qvalidatedlineedit.cpp
index 026ff8d0517..665d453b48f 100644
--- a/src/qt/qvalidatedlineedit.cpp
+++ b/src/qt/qvalidatedlineedit.cpp
@@ -126,3 +126,5 @@ bool QValidatedLineEdit::isValid()
 
     return valid;
 }
+
+#include <moc_qvalidatedlineedit.cpp>
diff --git a/src/qt/sendcoinsentry.cpp b/src/qt/sendcoinsentry.cpp
index 679457262dd..aa4c07dc4b0 100644
--- a/src/qt/sendcoinsentry.cpp
+++ b/src/qt/sendcoinsentry.cpp
@@ -238,3 +238,5 @@ bool SendCoinsEntry::updateLabel(const QString &address)
 
     return false;
 }
+
+#include <moc_sendcoinsentry.cpp>
diff --git a/test/lint/lint-includes.py b/test/lint/lint-includes.py
index 2e8417ea734..328946d83b5 100755
--- a/test/lint/lint-includes.py
+++ b/test/lint/lint-includes.py
@@ -70,7 +70,11 @@ def find_included_cpps():
         if e.returncode > 1:
             raise e
 
-    return included_cpps
+    # Exception: `#include <moc_*.cpp>` statements in src/qt source files are permitted.
+    # See:
+    # - https://doc.qt.io/qt-6/moc.html
+    # - https://cmake.org/cmake/help/latest/prop_tgt/AUTOMOC.html
+    return [i for i in included_cpps if not re.match(r"src/qt/[^:]+\.cpp:#include <moc_[^<>:]+\.cpp>$", i)]
 
 
 def find_extra_boosts():