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>

1 files changed, 6 insertions, 6 deletions

diff --git a/comphelper/qa/unit/variadictemplates.cxx b/comphelper/qa/unit/variadictemplates.cxx
index 20d47f89758a..587bded24702 100644
--- a/comphelper/qa/unit/variadictemplates.cxx
+++ b/comphelper/qa/unit/variadictemplates.cxx
@@ -7,7 +7,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-#include <boost/optional.hpp>
+#include <o3tl/optional.hxx>
 #include <sal/types.h>
 #include <comphelper/unwrapargs.hxx>
 #include <cppunit/TestAssert.h>
@@ -56,7 +56,7 @@ void extract(
 template <typename T>
 void extract(
     ::com::sun::star::uno::Sequence< ::com::sun::star::uno::Any> const& seq,
-    sal_Int32 nArg, ::boost::optional<T> & v,
+    sal_Int32 nArg, ::o3tl::optional<T> & v,
     ::com::sun::star::uno::Reference< ::com::sun::star::uno::XInterface>
     const& xErrorContext )
 {
@@ -104,22 +104,22 @@ void VariadicTemplatesTest::testUnwrapArgs() {
     ::com::sun::star::uno::Any tmp9(
         ::com::sun::star::uno::makeAny( tmp4 )
         );
-    ::boost::optional< ::com::sun::star::uno::Any > tmp10(
+    ::o3tl::optional< ::com::sun::star::uno::Any > tmp10(
         ::com::sun::star::uno::makeAny( tmp5 )
         );
-    ::boost::optional< ::com::sun::star::uno::Any > tmp11(
+    ::o3tl::optional< ::com::sun::star::uno::Any > tmp11(
         ::com::sun::star::uno::makeAny( tmp1 )
         );
 
     // test equality with the baseline and template specialization with
-    // boost::optional< T >
+    // o3tl::optional< T >
     try {
         ::com::sun::star::uno::Sequence< ::com::sun::star::uno::Any > seq1(
             static_cast< sal_uInt32 >( 5 ) );
         ::com::sun::star::uno::Sequence< ::com::sun::star::uno::Any > seq2(
             static_cast< sal_uInt32 >( 5 ) );
 
-        // tmp11 should be ignored as it is ::boost::optional< T >
+        // tmp11 should be ignored as it is ::o3tl::optional< T >
         ::comphelper::unwrapArgs( seq1, tmp6, tmp7, tmp8, tmp9, tmp10, tmp11 );
         unwrapArgsBaseline( seq2, tmp6, tmp7, tmp8, tmp9, tmp10 );
         ::com::sun::star::uno::Any* p1 = seq1.getArray();