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>

2 files changed, 8 insertions, 2 deletions

diff --git a/i18nlangtag/source/isolang/isolang.cxx b/i18nlangtag/source/isolang/isolang.cxx
index 3d8da21708b1..60fbe5ff4e0a 100644
--- a/i18nlangtag/source/isolang/isolang.cxx
+++ b/i18nlangtag/source/isolang/isolang.cxx
@@ -104,6 +104,8 @@ struct Bcp47CountryEntry
     css::lang::Locale getLocale() const;
 };
 
+namespace {
+
 struct IsoLangEngEntry
 {
     LanguageType        mnLang;
@@ -123,6 +125,7 @@ struct IsoLangOtherEntry
     const sal_Char*     mpLanguage;
 };
 
+}
 
 // Entries for languages are lower case, for countries upper case, as
 // recommended by rfc5646 (obsoletes rfc4646 (obsoletes rfc3066 (obsoletes
@@ -1412,6 +1415,7 @@ LanguageType MsLangId::Conversion::convertIsoNamesToLanguage( const OString& rLa
     return convertIsoNamesToLanguage( aLang, aCountry, false);
 }
 
+namespace {
 
 struct IsoLangGLIBCModifiersEntry
 {
@@ -1421,6 +1425,8 @@ struct IsoLangGLIBCModifiersEntry
     sal_Char      maAtString[9];
 };
 
+}
+
 static IsoLangGLIBCModifiersEntry const aImplIsoLangGLIBCModifiersEntries[] =
 {
     // MS-LANGID codes               ISO639-1/2/3 ISO3166            glibc modifier
diff --git a/i18nlangtag/source/languagetag/languagetag.cxx b/i18nlangtag/source/languagetag/languagetag.cxx
index 7f580dfc9dd3..ef47e54579bc 100644
--- a/i18nlangtag/source/languagetag/languagetag.cxx
+++ b/i18nlangtag/source/languagetag/languagetag.cxx
@@ -33,6 +33,7 @@
 
 using namespace com::sun::star;
 
+namespace {
 
 // Helper to ensure lt_error_t is free'd
 struct myLtError
@@ -43,7 +44,6 @@ struct myLtError
 };
 
 // "statics" to be returned as const reference to an empty locale and string.
-namespace {
 struct theEmptyLocale : public rtl::Static< lang::Locale, theEmptyLocale > {};
 struct theEmptyBcp47 : public rtl::Static< OUString, theEmptyBcp47 > {};
 }
@@ -141,6 +141,7 @@ bool LanguageTag::isOnTheFlyID( LanguageType nLang )
         LANGUAGE_ON_THE_FLY_SUB_START <= nSub && nSub <= LANGUAGE_ON_THE_FLY_SUB_END;
 }
 
+namespace {
 
 /** A reference holder for liblangtag data de/initialization, one static
     instance. Currently implemented such that the first "ref" inits and dtor
@@ -165,7 +166,6 @@ private:
     static void teardown();
 };
 
-namespace {
 struct theDataRef : public rtl::Static< LiblangtagDataRef, theDataRef > {};
 }