added constness_ptr as pointer wrapper to ensure actual method constness [skip ci]

Author: firewave

lib/constnessptr.h

@@ -0,0 +1,72 @@
+/* -*- C++ -*-
+ * Cppcheck - A tool for static C/C++ code analysis
+ * Copyright (C) 2007-2025 Cppcheck team.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+//---------------------------------------------------------------------------
+#ifndef constnessPtrH
+#define constnessPtrH
+//---------------------------------------------------------------------------
+
+#include "config.h"
+
+// as std::optional behaves similarly so we could use that instead of if we ever move to C++17.
+// it is not a simple drop-in as our "operator bool()" indicates if the pointer is non-null
+// whereas std::optional indicates if a value is set.
+//
+// This is similar to std::experimental::propagate_const
+// see https://en.cppreference.com/w/cpp/experimental/propagate_const
+template<typename T>
+class constness_ptr
+{
+public:
+    explicit constness_ptr(T* p)
+        : mPtr(p)
+    {}
+
+    T* get() NOEXCEPT {
+        return mPtr;
+    }
+
+    const T* get() const NOEXCEPT {
+        return mPtr;
+    }
+
+    T* operator->() NOEXCEPT {
+        return mPtr;
+    }
+
+    const T* operator->() const NOEXCEPT {
+        return mPtr;
+    }
+
+    T& operator*() NOEXCEPT {
+        return *mPtr;
+    }
+
+    const T& operator*() const NOEXCEPT {
+        return *mPtr;
+    }
+
+    explicit operator bool() const NOEXCEPT {
+        return mPtr != nullptr;
+    }
+
+private:
+    T* mPtr;
+};
+
+#endif // constnessPtrH

lib/cppcheck.vcxproj

@@ -133,6 +133,7 @@
     <ClInclude Include="clangimport.h" />
     <ClInclude Include="color.h" />
     <ClInclude Include="config.h" />
+    <ClInclude Include="constnessptr.h" />
     <ClInclude Include="cppcheck.h" />
     <ClInclude Include="ctu.h" />
     <ClInclude Include="errorlogger.h" />

test/constness_ptr/constness_ptr_test.cpp

@@ -0,0 +1,26 @@
+#include "constnessptr.h"
+#include "utils.h"
+
+struct S
+{
+    void f();
+    void f_c() const;
+};
+
+struct S1
+{
+    explicit S1(S*s) : mS(s) {}
+    constness_ptr<S> mS;
+};
+
+void f()
+{
+    S s;
+    S1 s1(&s);
+    s1.mS->f();
+    s1.mS->f_c();
+    utils::as_const(s1).mS->f_c();
+#ifdef BAD
+    utils::as_const(s1).mS->f();
+#endif
+}

test/constness_ptr/run.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"/
+LIBDIR="$DIR"../../lib
+
+ec=0
+gcc -c constness_ptr_test.cpp -Wall -Wextra -I$LIBDIR || ec=1
+gcc -c constness_ptr_test.cpp -Wall -Wextra -I$LIBDIR -DBAD && ec=1
+exit $ec

tools/dmake/dmake.cpp

@@ -468,6 +468,7 @@ int main(int argc, char **argv)
     libfiles_h.emplace("analyzer.h");
     libfiles_h.emplace("calculate.h");
     libfiles_h.emplace("config.h");
+    libfiles_h.emplace("constnessptr.h");
     libfiles_h.emplace("filesettings.h");
     libfiles_h.emplace("findtoken.h");
     libfiles_h.emplace("json.h");