New loplugin:conststringvar

Change-Id: I16648b018ed0f69a085322cfb88481ee2a0c27ca

1 files changed, 136 insertions, 0 deletions

diff --git a/compilerplugins/clang/conststringvar.cxx b/compilerplugins/clang/conststringvar.cxx
new file mode 100644
index 000000000000..58a94e559428
--- /dev/null
+++ b/compilerplugins/clang/conststringvar.cxx
@@ -0,0 +1,136 @@
+/* -*- 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 <set>
+#include <stack>
+
+#include "check.hxx"
+#include "plugin.hxx"
+
+// Find non-const vars of 'char const *' type initialized with a const expr,
+// that could likely be const (and will then probably trigger further
+// loplugin:stringconstant findings).
+
+namespace {
+
+// It looks like Clang wrongly implements DR 4
+// (<http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#4>) and treats
+// a variable declared in an 'extern "..." {...}'-style linkage-specification as
+// if it contained the 'extern' specifier:
+bool hasExternalLinkage(VarDecl const * decl) {
+    if (decl->getLinkageAndVisibility().getLinkage() != ExternalLinkage) {
+        return false;
+    }
+    for (auto ctx = decl->getLexicalDeclContext();
+         ctx->getDeclKind() != Decl::TranslationUnit;
+         ctx = ctx->getLexicalParent())
+    {
+        if (auto ls = dyn_cast<LinkageSpecDecl>(ctx)) {
+            if (!ls->hasBraces()) {
+                return true;
+            }
+            if (auto prev = decl->getPreviousDecl()) {
+                return hasExternalLinkage(prev);
+            }
+            return !decl->isInAnonymousNamespace();
+        }
+    }
+    return true;
+}
+
+class ConstStringVar:
+    public RecursiveASTVisitor<ConstStringVar>, public loplugin::Plugin
+{
+public:
+    explicit ConstStringVar(InstantiationData const & data): Plugin(data) {}
+
+    void run() override {
+        if (compiler.getLangOpts().CPlusPlus) {
+                // clang::Expr::isCXX11ConstantExpr only works for C++
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+            for (auto v: vars_) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    "variable is only used as rvalue, should be const",
+                    v->getLocation())
+                    << v->getSourceRange();
+            }
+        }
+    }
+
+    bool TraverseImplicitCastExpr(ImplicitCastExpr * expr) {
+        bool pushed = false;
+        if (expr->getCastKind() == CK_LValueToRValue) {
+            if (auto dr = dyn_cast<DeclRefExpr>(
+                    expr->getSubExpr()->IgnoreParenImpCasts()))
+            {
+                if (auto vd = dyn_cast<VarDecl>(dr->getDecl())) {
+                    if (vars_.find(vd->getCanonicalDecl()) != vars_.end()) {
+                        casted_.push(dr);
+                        pushed = true;
+                    }
+                }
+            }
+        }
+        bool b = RecursiveASTVisitor::TraverseImplicitCastExpr(expr);
+        if (pushed) {
+            casted_.pop();
+        }
+        return b;
+    }
+
+    bool VisitVarDecl(VarDecl const * decl) {
+        if (ignoreLocation(decl)) {
+            return true;
+        }
+        if (decl != decl->getCanonicalDecl()) {
+            return true;
+        }
+        if (isa<ParmVarDecl>(decl) || hasExternalLinkage(decl)) {
+            return true;
+        }
+        if (!loplugin::TypeCheck(decl->getType()).NonConstVolatile().Pointer()
+            .Const().Char())
+        {
+            return true;
+        }
+        auto init = decl->getAnyInitializer();
+        if (init == nullptr) {
+            return true;
+        }
+        APValue v;
+        if (!init->isCXX11ConstantExpr(compiler.getASTContext(), &v)) {
+            return true;
+        }
+        vars_.insert(decl);
+        return true;
+    }
+
+    bool VisitDeclRefExpr(DeclRefExpr const * expr) {
+        if (!casted_.empty() && expr == casted_.top()) {
+            return true;
+        }
+        auto vd = dyn_cast<VarDecl>(expr->getDecl());
+        if (vd == nullptr) {
+            return true;
+        }
+        vars_.erase(vd->getCanonicalDecl());
+        return true;
+    }
+
+private:
+    std::set<VarDecl const *> vars_;
+    std::stack<DeclRefExpr const *> casted_;
+};
+
+loplugin::Plugin::Registration<ConstStringVar> X("conststringvar");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */