Introduce o3tl::optional as an alias for std::optional

...with a boost::optional fallback for Xcode < 10 (as std::optional is only
available starting with Xcode 10 according to
<https://en.cppreference.com/w/cpp/compiler_support>, and our baseline for iOS
and macOS is still Xcode 9.3 according to README.md).  And mechanically rewrite
all code to use o3tl::optional instead of boost::optional.

One immediate benefit is that disabling -Wmaybe-uninitialized for GCC as per
fed7c3deb3f4ec81f78967c2d7f3c4554398cb9d "Slience bogus
-Werror=maybe-uninitialized" should no longer be necessary (and whose check
happened to no longer trigger for GCC 10 trunk, even though that compiler would
still emit bogus -Wmaybe-uninitialized for uses of boost::optional under
--enable-optimized, which made me ponder whether this switch from
boost::optional to std::optional would be a useful thing to do; I keep that
configure.ac check for now, though, and will only remove it in a follow up
commit).

Another longer-term benefit is that the code is now already in good shape for an
eventual switch to std::optional (a switch we would have done anyway once we no
longer need to support Xcode < 10).

Only desktop/qa/desktop_lib/test_desktop_lib.cxx heavily uses
boost::property_tree::ptree::get_child_optional returning boost::optional, so
let it keep using boost::optional for now.

After a number of preceding commits have paved the way for this change, this
commit is completely mechanical, done with

> git ls-files -z | grep -vz -e '^bin/find-unneeded-includes$' -e '^configure.ac$' -e '^desktop/qa/desktop_lib/test_desktop_lib.cxx$' -e '^dictionaries$' -e '^external/' -e '^helpcontent2$' -e '^include/IwyuFilter_include.yaml$' -e '^sc/IwyuFilter_sc.yaml$' -e '^solenv/gdb/boost/optional.py$' -e '^solenv/vs/LibreOffice.natvis$' -e '^translations$' -e '\.svg$' | xargs -0 sed -i -E -e 's|\<boost(/optional)?/optional\.hpp\>|o3tl/optional.hxx|g' -e 's/\<boost(\s*)::(\s*)(make_)?optional\>/o3tl\1::\2\3optional/g' -e 's/\<boost(\s*)::(\s*)none\>/o3tl\1::\2nullopt/g'

(before committing include/o3tl/optional.hxx, and relying on some GNU features).
It excludes some files where mention of boost::optional et al should apparently
not be changed (and the sub-repo directory stubs).  It turned out that all uses
of boost::none across the code base were in combination with boost::optional, so
had all to be rewritten as o3tl::nullopt.

Change-Id: Ibfd9f4b3d5a8aee6e6eed310b988c4e5ffd8b11b
Reviewed-on: https://gerrit.libreoffice.org/84128
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

5 files changed, 9 insertions, 9 deletions

diff --git a/connectivity/inc/pch/precompiled_dbtools.hxx b/connectivity/inc/pch/precompiled_dbtools.hxx
index 18c96b84847e..ea2bc6c2e6cd 100644
--- a/connectivity/inc/pch/precompiled_dbtools.hxx
+++ b/connectivity/inc/pch/precompiled_dbtools.hxx
@@ -35,7 +35,7 @@
 #include <string_view>
 #include <utility>
 #include <vector>
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 #endif // PCH_LEVEL >= 1
 #if PCH_LEVEL >= 2
 #include <osl/diagnose.h>
diff --git a/connectivity/inc/pch/precompiled_file.hxx b/connectivity/inc/pch/precompiled_file.hxx
index 3b431975dc9a..45f42158b841 100644
--- a/connectivity/inc/pch/precompiled_file.hxx
+++ b/connectivity/inc/pch/precompiled_file.hxx
@@ -40,7 +40,7 @@
 #include <type_traits>
 #include <utility>
 #include <vector>
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 #endif // PCH_LEVEL >= 1
 #if PCH_LEVEL >= 2
 #include <osl/diagnose.h>
diff --git a/connectivity/inc/pch/precompiled_postgresql-sdbc-impl.hxx b/connectivity/inc/pch/precompiled_postgresql-sdbc-impl.hxx
index 9bb8f375b394..b27bca84af1b 100644
--- a/connectivity/inc/pch/precompiled_postgresql-sdbc-impl.hxx
+++ b/connectivity/inc/pch/precompiled_postgresql-sdbc-impl.hxx
@@ -22,7 +22,7 @@
 
 #if PCH_LEVEL >= 1
 #include <string.h>
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 #endif // PCH_LEVEL >= 1
 #if PCH_LEVEL >= 2
 #include <osl/module.h>
diff --git a/connectivity/source/commontools/dbmetadata.cxx b/connectivity/source/commontools/dbmetadata.cxx
index d345aec78cac..6d539a599f43 100644
--- a/connectivity/source/commontools/dbmetadata.cxx
+++ b/connectivity/source/commontools/dbmetadata.cxx
@@ -39,7 +39,7 @@
 #include <sal/macros.h>
 #include <sal/log.hxx>
 
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 
 
 namespace dbtools
@@ -72,8 +72,8 @@ namespace dbtools
         Reference< XDatabaseMetaData >  xConnectionMetaData;
         ::connectivity::DriversConfig   aDriverConfig;
 
-        ::boost::optional< OUString >    sCachedIdentifierQuoteString;
-        ::boost::optional< OUString >    sCachedCatalogSeparator;
+        ::o3tl::optional< OUString >    sCachedIdentifierQuoteString;
+        ::o3tl::optional< OUString >    sCachedCatalogSeparator;
 
         DatabaseMetaData_Impl()
             :xConnection()
@@ -155,7 +155,7 @@ namespace dbtools
 
 
         const OUString& lcl_getConnectionStringSetting(
-            const DatabaseMetaData_Impl& _metaData, ::boost::optional< OUString >& _cachedSetting,
+            const DatabaseMetaData_Impl& _metaData, ::o3tl::optional< OUString >& _cachedSetting,
             OUString (SAL_CALL XDatabaseMetaData::*_getter)() )
         {
             if ( !_cachedSetting )
diff --git a/connectivity/source/inc/java/io/Reader.hxx b/connectivity/source/inc/java/io/Reader.hxx
index 592d476def14..45d67bbd9b11 100644
--- a/connectivity/source/inc/java/io/Reader.hxx
+++ b/connectivity/source/inc/java/io/Reader.hxx
@@ -23,7 +23,7 @@
 #include <java/lang/Object.hxx>
 #include <cppuhelper/implbase.hxx>
 #include <com/sun/star/io/XInputStream.hpp>
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 
 namespace connectivity
 {
@@ -36,7 +36,7 @@ namespace connectivity
     // static Data for the Class
         static jclass theClass;
         virtual ~java_io_Reader() override;
-        boost::optional<char> m_buf;
+        o3tl::optional<char> m_buf;
     public:
         virtual jclass getMyClass() const override;
         // a Constructor, that is needed for when Returning the Object is needed: