Extend loplugin:external to warn about classes

...following up on 314f15bff08b76bf96acf99141776ef64d2f1355 "Extend
loplugin:external to warn about enums".

Cases where free functions were moved into an unnamed namespace along with a
class, to not break ADL, are in:

  filter/source/svg/svgexport.cxx
  sc/source/filter/excel/xelink.cxx
  sc/source/filter/excel/xilink.cxx
  svx/source/sdr/contact/viewobjectcontactofunocontrol.cxx

All other free functions mentioning moved classes appear to be harmless and not
give rise to (silent, even) ADL breakage.  (One remaining TODO in
compilerplugins/clang/external.cxx is that derived classes are not covered by
computeAffectedTypes, even though they could also be affected by ADL-breakage---
but don't seem to be in any acutal case across the code base.)

For friend declarations using elaborate type specifiers, like

  class C1 {};
  class C2 { friend class C1; };

* If C2 (but not C1) is moved into an unnamed namespace, the friend declaration
must be changed to not use an elaborate type specifier (i.e., "friend C1;"; see
C++17 [namespace.memdef]/3: "If the name in a friend declaration is neither
qualified nor a template-id and the declaration is a function or an
elaborated-type-specifier, the lookup to determine whether the entity has been
previously declared shall not consider any scopes outside the innermost
enclosing namespace.")

* If C1 (but not C2) is moved into an unnamed namespace, the friend declaration
must be changed too, see <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71882>
"elaborated-type-specifier friend not looked up in unnamed namespace".

Apart from that, to keep changes simple and mostly mechanical (which should help
avoid regressions), out-of-line definitions of class members have been left in
the enclosing (named) namespace.  But explicit specializations of class
templates had to be moved into the unnamed namespace to appease
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92598> "explicit specialization of
template from unnamed namespace using unqualified-id in enclosing namespace".

Also, accompanying declarations (of e.g. typedefs or static variables) that
could arguably be moved into the unnamed namespace too have been left alone.

And in some cases, mention of affected types in blacklists in other loplugins
needed to be adapted.

And sc/qa/unit/mark_test.cxx uses a hack of including other .cxx, one of which
is sc/source/core/data/segmenttree.cxx where e.g. ScFlatUInt16SegmentsImpl is
not moved into an unnamed namespace (because it is declared in
sc/inc/segmenttree.hxx), but its base ScFlatSegmentsImpl is.  GCC warns about
such combinations with enabled-by-default -Wsubobject-linkage, but "The compiler
doesn’t give this warning for types defined in the main .C file, as those are
unlikely to have multiple definitions."
(<https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Warning-Options.html>)  The
warned-about classes also don't have multiple definitions in the given test, so
disable the warning when including the .cxx.

Change-Id: Ib694094c0d8168be68f8fe90dfd0acbb66a3f1e4
Reviewed-on: https://gerrit.libreoffice.org/83239
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

4 files changed, 15 insertions, 4 deletions

diff --git a/sot/source/base/exchange.cxx b/sot/source/base/exchange.cxx
index da90eef263d7..4888a366ec71 100644
--- a/sot/source/base/exchange.cxx
+++ b/sot/source/base/exchange.cxx
@@ -34,6 +34,8 @@
 using namespace::com::sun::star::uno;
 using namespace::com::sun::star::datatransfer;
 
+namespace {
+
 /*
  *  These tables contain all MimeTypes, format identifiers, and types used in
  *  the Office. The table is sorted by the format string ID, and each ID is
@@ -47,8 +49,6 @@ struct DataFlavorRepresentation
     const css::uno::Type*  pType;
 };
 
-namespace
-{
     struct ImplFormatArray_Impl
     {
         const DataFlavorRepresentation* operator()()
diff --git a/sot/source/base/formats.cxx b/sot/source/base/formats.cxx
index 51c6b157496f..f911b0b89c0c 100644
--- a/sot/source/base/formats.cxx
+++ b/sot/source/base/formats.cxx
@@ -49,6 +49,8 @@ using namespace ::com::sun::star::datatransfer;
  *  it appears in the list.
  */
 
+namespace {
+
 struct SotDestinationEntry_Impl
 {
     SotExchangeDest const   nDestination;
@@ -58,8 +60,6 @@ struct SotDestinationEntry_Impl
     const SotAction_Impl*   aLinkActions;
 };
 
-namespace
-{
 /*
  *  Via this table, the destination, existing data formats and the desired action
  *  are assigned to an action and the data format to be used in it. The table is
diff --git a/sot/source/sdstor/stgio.cxx b/sot/source/sdstor/stgio.cxx
index 026881b9a7d7..08f023c5f52a 100644
--- a/sot/source/sdstor/stgio.cxx
+++ b/sot/source/sdstor/stgio.cxx
@@ -154,6 +154,7 @@ bool StgIo::CommitAll()
     return false;
 }
 
+namespace {
 
 class EasyFat
 {
@@ -171,6 +172,8 @@ public:
     bool HasUnrefChains() const;
 };
 
+}
+
 EasyFat::EasyFat( StgIo& rIo, StgStrm* pFatStream, sal_Int32 nPSize )
 {
     nPages = pFatStream->GetSize() >> 2;
@@ -236,6 +239,8 @@ FatError EasyFat::Mark( sal_Int32 nPage, sal_Int32 nCount, sal_Int32 nExpect )
     return FatError::Ok;
 }
 
+namespace {
+
 class Validator
 {
     FatError nError;
@@ -255,6 +260,8 @@ public:
     bool IsError() const { return nError != FatError::Ok; }
 };
 
+}
+
 Validator::Validator( StgIo &rIoP )
     : aSmallFat( rIoP, rIoP.m_pDataFAT, 1 << rIoP.m_aHdr.GetDataPageSize() ),
       aFat( rIoP, rIoP.m_pFAT, 1 << rIoP.m_aHdr.GetPageSize() ),
diff --git a/sot/source/sdstor/ucbstorage.cxx b/sot/source/sdstor/ucbstorage.cxx
index 22ef098bbbf4..9edd26aae4eb 100644
--- a/sot/source/sdstor/ucbstorage.cxx
+++ b/sot/source/sdstor/ucbstorage.cxx
@@ -79,6 +79,9 @@ static int nOpenStreams=0;
 #endif
 
 typedef ::cppu::WeakImplHelper < XInputStream, XSeekable > FileInputStreamWrapper_Base;
+
+namespace {
+
 class FileStreamWrapper_Impl : public FileInputStreamWrapper_Base
 {
 protected:
@@ -104,6 +107,7 @@ protected:
     void checkError();
 };
 
+}
 
 FileStreamWrapper_Impl::FileStreamWrapper_Impl( const OUString& rName )
     : m_aURL( rName )