Extend loplugin:stringview to OUStringBuffer::copy

(Somewhat oddly, there is no OStringBuffer::copy counterpart.)

This required some modification to StringView::VisitCXXConstructExpr to avoid

> In file included from odk/qa/checkapi/checkapi.cxx:29:
> In file included from workdir/CustomTarget/odk/allheaders/allheaders.hxx:351:
> In file included from instdir/sdk/include/rtl/math.hxx:31:
> instdir/sdk/include/rtl/ustrbuf.hxx:1687:16: error: rather than copy, pass with a view using subView() [loplugin:stringview]
>         return copy( beginIndex, getLength() - beginIndex );
>                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

while building CppunitTest_odk_checkapi as external C++03 code, where the
returned value is wrapped in a CXXConstructExpr.  And testing for that case
required a new CompilerTest_compilerplugins_clang-c++03 that uses gb_CXX03FLAGS
and needs to not set LIBO_INTERNAL_ONLY (via gb_CompilerTest_set_external_code),
as compiling as C++03 would otherwise generate lots of errors like unknown
char16_t at include/sal/types.h:118.  (There was a choice whether to name the
new test "-c++03" or "-external", but the issue it tests is caused more by the
code being compiled with C++03 than by this being external code, see above.)

Change-Id: I873a9c5a70d3ea949cf13a169d46920b71282712
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/130036
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

3 files changed, 37 insertions, 2 deletions

diff --git a/compilerplugins/clang/stringview.cxx b/compilerplugins/clang/stringview.cxx
index 4c31c348b357..c81b04ebace5 100644
--- a/compilerplugins/clang/stringview.cxx
+++ b/compilerplugins/clang/stringview.cxx
@@ -134,7 +134,8 @@ void StringView::handleSubExprThatCouldBeView(Expr const* subExpr)
     auto const e = e0->IgnoreParens();
     auto const tc = loplugin::TypeCheck(e->getType());
     if (!(tc.Class("OString").Namespace("rtl").GlobalNamespace()
-          || tc.Class("OUString").Namespace("rtl").GlobalNamespace()))
+          || tc.Class("OUString").Namespace("rtl").GlobalNamespace()
+          || tc.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace()))
     {
         return;
     }
@@ -272,7 +273,8 @@ void StringView::handleCXXMemberCallExpr(CXXMemberCallExpr const* expr)
     if (auto const dc2 = dc1.Function("copy"))
     {
         if (dc2.Class("OString").Namespace("rtl").GlobalNamespace()
-            || dc2.Class("OUString").Namespace("rtl").GlobalNamespace())
+            || dc2.Class("OUString").Namespace("rtl").GlobalNamespace()
+            || dc2.Class("OUStringBuffer").Namespace("rtl").GlobalNamespace())
         {
             report(DiagnosticsEngine::Warning, "rather than copy, pass with a view using subView()",
                    expr->getExprLoc())
@@ -343,6 +345,10 @@ bool StringView::VisitCXXConstructExpr(CXXConstructExpr const* expr)
     {
         return true;
     }
+    if (!compat::CPlusPlus17(compiler.getLangOpts()) && expr->isElidable()) // external C++03 code
+    {
+        return true;
+    }
     if (expr->getNumArgs() > 0)
         handleSubExprThatCouldBeView(expr->getArg(0));
     return true;
diff --git a/compilerplugins/clang/test/stringview-c++03.cxx b/compilerplugins/clang/test/stringview-c++03.cxx
new file mode 100644
index 000000000000..1824ac9d02ce
--- /dev/null
+++ b/compilerplugins/clang/test/stringview-c++03.cxx
@@ -0,0 +1,21 @@
+/* -*- 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 <rtl/ustrbuf.hxx>
+
+// expected-no-diagnostics
+
+rtl::OUStringBuffer nowarn(rtl::OUStringBuffer const& s, sal_Int32 n)
+{
+    return s.copy(n, s.getLength() - n);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
diff --git a/compilerplugins/clang/test/stringview.cxx b/compilerplugins/clang/test/stringview.cxx
index 16e294a6eeb7..a679ec59ea45 100644
--- a/compilerplugins/clang/test/stringview.cxx
+++ b/compilerplugins/clang/test/stringview.cxx
@@ -61,6 +61,14 @@ void f1(OString s1)
 }
 void f1(OUStringBuffer s1)
 {
+    // expected-error@+1 {{rather than copy, pass with a view using subView() [loplugin:stringview]}}
+    call_view(s1.copy(1, 2));
+    // expected-error@+1 {{rather than copy, pass with a view using subView() [loplugin:stringview]}}
+    call_view(s1.copy(1));
+    // expected-error@+1 {{rather than copy, pass with a view using subView() [loplugin:stringview]}}
+    ConstructWithView(s1.copy(1, 2));
+    // expected-error@+1 {{rather than copy, pass with a view using subView() [loplugin:stringview]}}
+    ConstructWithView(s1.copy(1));
     // expected-error@+1 {{rather than call toString, pass with a view [loplugin:stringview]}}
     call_view(s1.toString());
     // expected-error@+1 {{rather than call toString, pass with a view [loplugin:stringview]}}