A plugin to find suboptimal equalsIgnoreAsciiCaseAscii[L] calls

Change-Id: Id2572982ca899223b89016ee7482ccb960032805

compilerplugins/clang/literalalternative.cxx

+/* -*- 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"
+
+// Find those calls of rtl::OUString::equalsIgnoreAsciiCaseAscii and
+// rtl::OUString::equalsIgnoreAsciiCaseAsciiL that could be simplified to call
+// rtl::OUString::equalsIgnoreAsciiCase instead:
+
+namespace {
+
+class LiteralAlternative:
+    public RecursiveASTVisitor<LiteralAlternative>, public loplugin::Plugin
+{
+public:
+    explicit LiteralAlternative(ASTContext & context): Plugin(context) {}
+
+    virtual void run() { TraverseDecl(context.getTranslationUnitDecl()); }
+
+    bool VisitCallExpr(CallExpr * expr);
+};
+
+bool LiteralAlternative::VisitCallExpr(CallExpr * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    FunctionDecl const * fdecl = expr->getDirectCallee();
+    if (fdecl == nullptr) {
+        return true;
+    }
+    std::string qname { fdecl->getQualifiedNameAsString() };
+    if (qname == "rtl::OUString::equalsIgnoreAsciiCaseAscii"
+        && fdecl->getNumParams() == 1 && expr->getNumArgs() == 1)
+    {
+        // equalsIgnoreAsciiCaseAscii("foo") -> equalsIngoreAsciiCase("foo"):
+        StringLiteral const * lit
+            = dyn_cast<StringLiteral>(expr->getArg(0)->IgnoreParenImpCasts());
+        if (lit != nullptr) {
+            report(
+                DiagnosticsEngine::Warning,
+                ("rewrite call of rtl::OUString::equalsIgnoreAsciiCaseAscii"
+                 " with string literal argument as call of"
+                 " rtl::OUString::equalsIgnoreAsciiCase"),
+                expr->getExprLoc());
+                //TODO: a better loc (the "equalsIgnoreAsciiCaseAscii" part)?
+        }
+        return true;
+    }
+    if (qname == "rtl::OUString::equalsIgnoreAsciiCaseAsciiL"
+        && fdecl->getNumParams() == 2 && expr->getNumArgs() == 2)
+    {
+        // equalsIgnoreAsciiCaseAsciiL("foo", 3) -> equalsIngoreAsciiCase("foo")
+        // especially also for
+        // equalsIgnoreAsciiCaseAsciiL(RTL_CONSTASCII_STRINGPARAM("foo")), where
+        // RTL_CONSTASCII_STRINGPARAM expands to complicated expressions
+        // involving (&(X)[0] sub-expressions (and it might or might not be
+        // better to handle that at the level of non-expanded macros instead,
+        // but I have not found out how to do that yet anyway):
+        APSInt res;
+        if (expr->getArg(1)->isIntegerConstantExpr(res, context)) {
+            Expr const * arg0 = expr->getArg(0)->IgnoreParenImpCasts();
+            StringLiteral const * lit = dyn_cast<StringLiteral>(arg0);
+            bool match = false;
+            if (lit != nullptr) {
+                match = res == lit->getLength();
+            } else {
+                UnaryOperator const * op = dyn_cast<UnaryOperator>(arg0);
+                if (op != nullptr && op->getOpcode() == UO_AddrOf) {
+                    ArraySubscriptExpr const * subs
+                        = dyn_cast<ArraySubscriptExpr>(
+                            op->getSubExpr()->IgnoreParenImpCasts());
+                    if (subs != nullptr) {
+                        lit = dyn_cast<StringLiteral>(
+                            subs->getBase()->IgnoreParenImpCasts());
+                        match = lit != nullptr
+                            && subs->getIdx()->isIntegerConstantExpr(
+                                res, context)
+                            && res == 0;
+                    }
+                }
+            }
+            if (match) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("rewrite call of"
+                     " rtl::OUString::equalsIgnoreAsciiCaseAsciiL with string"
+                     " literal and matching length arguments as call of"
+                     " rtl::OUString::equalsIgnoreAsciiCase"),
+                    expr->getExprLoc());
+                    //TODO: a better loc (the "equalsIgnoreAsciiCaseAsciiL"
+                    // part)?
+            }
+        }
+        return true;
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration< LiteralAlternative > X("literalalternative");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */