new loplugin:unnecessarygetstr

which prevents constructing unnecessary temporaries via getStr()

Change-Id: I9ca70893a10e954b5ee0e6ad6098660ee24c2bef
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/150170
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 177 insertions, 0 deletions

diff --git a/compilerplugins/clang/test/unnecessarygetstr.cxx b/compilerplugins/clang/test/unnecessarygetstr.cxx
new file mode 100644
index 000000000000..68175872a4ea
--- /dev/null
+++ b/compilerplugins/clang/test/unnecessarygetstr.cxx
@@ -0,0 +1,55 @@
+/* -*- 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 <sal/config.h>
+
+#include <ostream>
+#include <string_view>
+
+#include <rtl/strbuf.hxx>
+#include <rtl/string.hxx>
+#include <rtl/ustrbuf.hxx>
+#include <rtl/ustring.hxx>
+#include <sal/log.hxx>
+
+void f1(bool, const OString& s);
+struct Foo
+{
+    void f1(bool, const OString& s);
+};
+void test1(Foo& foo)
+{
+    OString s;
+    // expected-error@+1 {{unnecessary call to 'getStr' when passing to OString arg [loplugin:unnecessarygetstr]}}
+    f1(true, s.getStr());
+    // expected-error@+1 {{unnecessary call to 'getStr' when passing to OString arg [loplugin:unnecessarygetstr]}}
+    foo.f1(true, s.getStr());
+
+    // avoid false +
+    OString aVal = "xx";
+    OUString aCompText
+        = "xx" + OUString(aVal.getStr(), aVal.getLength(), RTL_TEXTENCODING_ASCII_US);
+    (void)aCompText;
+}
+
+// call to param that takes string_view
+void f2(bool, std::string_view);
+struct Foo2
+{
+    void f2(bool, std::string_view);
+};
+void test2(Foo2& foo)
+{
+    OString s;
+    // expected-error@+1 {{unnecessary call to 'getStr' when passing to string_view arg [loplugin:unnecessarygetstr]}}
+    f2(true, s.getStr());
+    // expected-error@+1 {{unnecessary call to 'getStr' when passing to string_view arg [loplugin:unnecessarygetstr]}}
+    foo.f2(true, s.getStr());
+}
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/unnecessarygetstr.cxx b/compilerplugins/clang/unnecessarygetstr.cxx
new file mode 100644
index 000000000000..7ef5de6932d1
--- /dev/null
+++ b/compilerplugins/clang/unnecessarygetstr.cxx
@@ -0,0 +1,122 @@
+/* -*- 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"
+
+// Find matches of
+//
+//   foo(s.getStr())
+//
+// (for the rtl string classes) that can be written as just
+//
+//   foo(s)
+//
+// and warn about them, which prevents constructing unnecessary temporaries.
+
+namespace
+{
+class UnnecessaryGetStr final : public loplugin::FilteringPlugin<UnnecessaryGetStr>
+{
+public:
+    explicit UnnecessaryGetStr(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    bool VisitCallExpr(CallExpr* callExpr)
+    {
+        if (ignoreLocation(callExpr))
+            return true;
+        const FunctionDecl* func = callExpr->getDirectCallee();
+        if (!func)
+            return true;
+        unsigned const n = std::min(func->getNumParams(), callExpr->getNumArgs());
+        for (unsigned i = 0; i != n; ++i)
+        {
+            auto arg = callExpr->getArg(i);
+            if (auto matTemp = dyn_cast<MaterializeTemporaryExpr>(arg))
+            {
+                auto cxxConstruct = dyn_cast<CXXConstructExpr>(matTemp->IgnoreImplicit());
+                if (!cxxConstruct || cxxConstruct->getNumArgs() < 1
+                    || cxxConstruct->getNumArgs() > 2)
+                    continue;
+                auto const tc1 = loplugin::TypeCheck(cxxConstruct->getConstructor()->getParent());
+                if (!(tc1.Class("OString").Namespace("rtl").GlobalNamespace()
+                      || tc1.Class("OUString").Namespace("rtl").GlobalNamespace()))
+                    continue;
+                auto e = dyn_cast<CXXMemberCallExpr>(cxxConstruct->getArg(0)->IgnoreImplicit());
+                if (!e)
+                    continue;
+                auto const t = e->getObjectType();
+                auto const tc2 = loplugin::TypeCheck(t);
+                if (!(tc2.Class("OString").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OUString").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OStringBuffer").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()))
+                    continue;
+                if (!loplugin::DeclCheck(e->getMethodDecl()).Function("getStr"))
+                    continue;
+                report(DiagnosticsEngine::Warning,
+                       "unnecessary call to 'getStr' when passing to OString arg", e->getExprLoc())
+                    << e->getSourceRange();
+            }
+            else if (auto impCast = dyn_cast<ImplicitCastExpr>(arg))
+            {
+                auto cxxConstruct = dyn_cast<CXXConstructExpr>(impCast->getSubExpr());
+                if (!cxxConstruct || cxxConstruct->getNumArgs() < 1
+                    || cxxConstruct->getNumArgs() > 2)
+                    continue;
+                auto const tc1 = loplugin::TypeCheck(cxxConstruct->getConstructor()->getParent());
+                if (!(tc1.ClassOrStruct("basic_string_view").StdNamespace()))
+                    continue;
+                auto e = dyn_cast<CXXMemberCallExpr>(cxxConstruct->getArg(0)->IgnoreImplicit());
+                if (!e)
+                    continue;
+                auto const t = e->getObjectType();
+                auto const tc2 = loplugin::TypeCheck(t);
+                if (!(tc2.Class("OString").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OUString").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OStringBuffer").Namespace("rtl").GlobalNamespace()
+                      || tc2.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()))
+                    continue;
+                if (!loplugin::DeclCheck(e->getMethodDecl()).Function("getStr"))
+                    continue;
+                report(DiagnosticsEngine::Warning,
+                       "unnecessary call to 'getStr' when passing to string_view arg",
+                       e->getExprLoc())
+                    << e->getSourceRange();
+            }
+        }
+        return true;
+    }
+
+    bool preRun() override { return compiler.getLangOpts().CPlusPlus; }
+
+private:
+    void run() override
+    {
+        if (preRun())
+        {
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+        }
+    }
+};
+
+loplugin::Plugin::Registration<UnnecessaryGetStr> unnecessarygetstr("unnecessarygetstr");
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */