new loplugin: externalandnotdefined

Find "missing headers," where a function is declared directly in the
.cxx (as extern) and not defined, and should arguably instead be declared
in an include file.

Change-Id: I6d83ee432b2ab0cd050aec2b27c3658d32ac02a2

1 files changed, 79 insertions, 0 deletions

diff --git a/compilerplugins/clang/externandnotdefined.cxx b/compilerplugins/clang/externandnotdefined.cxx
new file mode 100644
index 000000000000..e66247fa1fad
--- /dev/null
+++ b/compilerplugins/clang/externandnotdefined.cxx
@@ -0,0 +1,79 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * 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 <string>
+
+#include "plugin.hxx"
+#include "compat.hxx"
+
+// Having an extern prototype for a method in a module and not actually declaring that method is dodgy.
+//
+
+namespace {
+
+class ExternAndNotDefined:
+    public RecursiveASTVisitor<ExternAndNotDefined>, public loplugin::Plugin
+{
+public:
+    explicit ExternAndNotDefined(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitFunctionDecl(const FunctionDecl * decl);
+};
+
+bool ExternAndNotDefined::VisitFunctionDecl(const FunctionDecl * functionDecl) {
+    if (ignoreLocation(functionDecl)) {
+        return true;
+    }
+    if (functionDecl->isDefined() || functionDecl->isPure()
+      || (compat::getLinkage(functionDecl->getLinkageAndVisibility())
+          != ExternalLinkage)) {
+        return true;
+    }
+    //TODO, filtering out anything template for now:
+    if (functionDecl->isDependentContext()) {
+        return true;
+    }
+    CXXRecordDecl const * r = dyn_cast<CXXRecordDecl>(functionDecl->getDeclContext());
+    if (r != nullptr && r->getTemplateSpecializationKind() != TSK_Undeclared) {
+        return true;
+    }
+    // this is the bison/flex C API, it has to be defined this way
+    string functionName = functionDecl->getNameAsString();
+    if (functionName == "yyerror" || functionName == "YYWarning" || functionName == "yyparse" || functionName == "yylex") {
+        return true;
+    }
+    // see vcl/unx/gtk/app/gtksys.cxx, typename conflicts prevent using the right include
+    if (functionName == "gdk_x11_screen_get_screen_number") {
+        return true;
+    }
+    SourceLocation spellingLocation = compiler.getSourceManager().getSpellingLoc(functionDecl->getLocation());
+    if (!compat::isInMainFile( compiler.getSourceManager(), spellingLocation)) {
+        return true;
+    }
+    StringRef fileName { compiler.getSourceManager().getFilename(functionDecl->getLocation()) };
+    // the filters use some kind of dynamic loading stunt
+    if (fileName.startswith(SRCDIR "/filter/qa/")) {
+        return true;
+    }
+    report(
+        DiagnosticsEngine::Warning,
+        "extern prototype in main file without definition",
+        functionDecl->getLocation())
+      << functionDecl->getSourceRange();
+    return true;
+}
+
+
+loplugin::Plugin::Registration< ExternAndNotDefined > X("externandnotdefined");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */