new loplugin:optionalbool

which warns against using the 'operator bool' conversion of
std::optional<bool> which can lead to interesting bugs

The bugs that this plugin have been submitted independantly,
so this change is just using has_value() in relevant places.

Change-Id: I259b837feeecddcb8cd1d7e5db1e85bf505907cb
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155978
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 115 insertions, 0 deletions

diff --git a/compilerplugins/clang/optionalbool.cxx b/compilerplugins/clang/optionalbool.cxx
new file mode 100644
index 000000000000..013bf1b4725c
--- /dev/null
+++ b/compilerplugins/clang/optionalbool.cxx
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include <cassert>
+#include <stack>
+
+#include "check.hxx"
+#include "plugin.hxx"
+#include "config_clang.h"
+
+// Check for uses of std::optional<bool> being assigned to bool, which generally does not do
+// what you would expect.
+
+namespace
+{
+class OptionalBool final : public loplugin::FilteringPlugin<OptionalBool>
+{
+public:
+    explicit OptionalBool(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    bool preRun() override
+    {
+        if (!compiler.getLangOpts().CPlusPlus)
+            return false;
+        return true;
+    }
+
+    void run() override
+    {
+        if (preRun())
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitIfStmt(const IfStmt* ifStmt)
+    {
+        if (ignoreLocation(ifStmt))
+            return true;
+        m_ignoreIfCondition = ifStmt->getCond()->IgnoreImplicit();
+        return true;
+    }
+
+    bool VisitCXXMemberCallExpr(const CXXMemberCallExpr* memberCall)
+    {
+        if (ignoreLocation(memberCall))
+            return true;
+        if (m_ignoreIfCondition == memberCall)
+            return true;
+        // check if we are calling a 'operator bool' conversion method
+        auto conversionDecl = dyn_cast_or_null<CXXConversionDecl>(memberCall->getMethodDecl());
+        if (!conversionDecl || !conversionDecl->getConversionType()->isBooleanType())
+            return true;
+        auto ctsd = dyn_cast_or_null<ClassTemplateSpecializationDecl>(
+            memberCall->getObjectType()->getAsRecordDecl());
+        if (!ctsd || ctsd->getTemplateArgs().size() < 1)
+            return true;
+        if (ctsd->getName() != "optional")
+            return true;
+        if (!ctsd->getTemplateArgs().get(0).getAsType()->isBooleanType())
+            return true;
+        report(DiagnosticsEngine::Warning,
+               "using conversion call to convert std::optional<bool> to bool probably does not do "
+               "what you expect, rather use has_value() or value_or()",
+               memberCall->getBeginLoc())
+            << memberCall->getSourceRange();
+        return true;
+    }
+
+private:
+    const Expr* m_ignoreIfCondition = nullptr;
+};
+
+loplugin::Plugin::Registration<OptionalBool> optionalbool("optionalbool");
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/test/optionalbool.cxx b/compilerplugins/clang/test/optionalbool.cxx
new file mode 100644
index 000000000000..02c3a84cf962
--- /dev/null
+++ b/compilerplugins/clang/test/optionalbool.cxx
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+#include "config_clang.h"
+#include <optional>
+
+namespace test1
+{
+std::optional<bool> get_optional_bool();
+void foo1()
+{
+    // expected-error@+1 {{using conversion call to convert std::optional<bool> to bool probably does not do what you expect, rather use has_value() or value_or() [loplugin:optionalbool]}}
+    bool foo(get_optional_bool());
+    (void)foo;
+
+    // no warning expected
+    if (std::optional<bool> b = get_optional_bool())
+        return;
+}
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */