Adding libc++ formattors for std::optional

[shafik]

Summary

Add formattors for libc++ std::optional and tests to verify the new Formattors.

[davide]

Some comments. Jonas looked at many formatters recently so he's in a good position to take a look.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/Makefile

10

commented out code?

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

22–23

ditto

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

15–39

You don't really need to se all these breakpoints.
You just need set one on the return and print all the types.
Also, an lldbInline python test here should suffice and it's probably more readable (grep for lldbInline).

source/Plugins/Language/CPlusPlus/CMakeLists.txt

15–16

Please sort this.

source/Plugins/Language/CPlusPlus/LibCxx.cpp

48–51

Can you use StringRef?

source/Plugins/Language/CPlusPlus/LibCxx.h

30–33

Please clang-format this patch.

source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp

60

Please remove this commented out code.

64

if you want to log diagnostics, you might consider using the LOG facility and then add these to the data formatters channel.

[jingham]

It seems a little odd to choose to represent this as an array with 1 element. I think I would be confused by that. You can maybe choose a better name like "value" for your cloned object. But it looks like it is also possible to make a Synthetic Child Provider that just replaces the value of the object with the value provided by the synthetic child provider. That's done in the Python front end by saying you have no children and then providing a the "get_value" method. It must be possible to do this from C++ as well, but it will take a little thought to figure out how that works. But that would be the most natural way to present this, I think.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

27–39

you can do this more cleanly with:

(self.target, _, _, bkpt) = lldbutil.run_to_source_breakpoint(self, "break here", lldb.SBFileSpec("main.cpp"))

40–49

I don't think you need this cleanup, you aren't adding any formatters, you're just testing built-in ones.

source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp

64

If you want to log this, get the formatters log channel and put the text there. Then somebody will see this when they turn on the log. An fprintf like this won't help anybody.

[shafik]

Address comments

• Applying clang-formt
• Refactoring OptionalFrontEnd to produce out that makes the underlying data look like an array
• Removing commented out code and left in debugging
• Using StringRef instead of const char *

[shafik]

@davide @jingham Thank you for the review, those were good catches and comments.

I have addressed them except for refactoring the test to use lldbInline which I will be working on now.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

15–39

This looks like a good idea, I will try it out and let you know.

source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp

64

Thank you for catching, I meant to remove this.

[davide]

This is getting really close. Please try the lldbInline test format and revert the unrelated bits and I'll take another look.
Thanks!

source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

971–972

this looks unrelated?

source/Plugins/Language/CPlusPlus/LibCxx.cpp

179–223

this looks like .. unrelated?

[shafik]

Removing unrelated changes due to applying clang-format to patch file with context.

[JDevlieghere]

Looks good to me, modulo the inline test (or the current comments addressed). Thanks Shafik!

[shafik]

Refactoring test to use lldbinline

[shafik]

@jingham @davide I believe I have addressed all your comments

[JDevlieghere]

LGTM, Thanks!

[davide]

Probably last round of comments. Thanks for your patience!

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/Makefile

8

you don't need this, it's implicit (-O0)

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

9

I do wonder if you need a decorator to indicate that this is a libcxx only test (and skip everywhere the library isn't supported).

source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

495

I'm a little nervous about this regex, but I think it's fine and I'll let Jim take another look in case I missed something.

source/Plugins/Language/CPlusPlus/LibCxx.cpp

42–51

This is really obscure to somebody who doesn't understand the type internally. Can you add a comment explaining the structure? (here or in the synthetic)

[jingham]

This looks fine. I agree with Davide that putting some description of the type you are formatting in comments somewhere would be make things easier for somebody else who might have to fix this (or to you when you've totally forgotten how this worked a year from now...)

I'm okay with this if you fix the things Davide asked about (except the regex, that looks right to me.)

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

9

Yes, you do need to mark this or you will get spurious failures at least on Windows, which turns off the libcxx category.

source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

495

That looks right to me, it's catching the type or a reference to it.

[shafik]

Addressing comments

• -O0 is not needed in Makefile
• engaged is not friendly terminology so switching to "Has Value"
• Switching test away from lldbinline style due to bug w/ .categories files which does not work on these tests

[shafik]

@davide One more pass

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

9

Switched back to the old style tests due to the .categories bug we discussed earlier.

source/Plugins/Language/CPlusPlus/LibCxx.cpp

42–51

That is a good point, I am looking at the cppreference page for it and I think maybe has_value might be an improvement.

[davide]

This is good, but please add a comment explaining the type before committing.

[shafik]

Adding additional comments

[davide]

Your latest update doesn't contain CMakeList.txt files and the Xcode project changes. That's why it failed to apply. Please upload a correct version and I'll commit it for you.

[davide]

Recommitted:

a11963323fc Recommit [DataFormatters] Add formatter for C++17 std::optional.

Authentication realm: https://llvm.org:443 LLVM Subversion repository
Password for 'davide': ***

Sending lldb/trunk/lldb.xcodeproj/project.pbxproj
Adding lldb/trunk/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional
Adding lldb/trunk/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/Makefile
Adding lldb/trunk/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py
Adding lldb/trunk/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp
Sending lldb/trunk/source/Plugins/Language/CPlusPlus/CMakeLists.txt
Sending lldb/trunk/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
Sending lldb/trunk/source/Plugins/Language/CPlusPlus/LibCxx.cpp
Sending lldb/trunk/source/Plugins/Language/CPlusPlus/LibCxx.h
Adding lldb/trunk/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp
Transmitting file data .........done
Committing transaction...
Committed revision 338156.
Committed a11963323fc to svn.

[davide]

I'm afraid I had to revert this again. It broke an ubuntu lldb-cmake bot which builds with clang-3.5 (which has no -std=c++17 support flag, as 17 wasn't there yet).

I'd recommend to update this patch with another decorator to skip places where -std=c++17 is not available doesn't work, and then we'll try again.

[davide]

Bot logs for completeness:

Session logs for test failures/errors/unexpected successes will go into directory 'logs-clang-3.5-i386'
Command invoked: /lldb-buildbot/lldbSlave/buildWorkingDir/scripts/../llvm/tools/lldb/test/dotest.py -A i386 -C clang-3.5 -v -s logs-clang-3.5-i386 -u CXXFLAGS -u CFLAGS --env ARCHIVER=ar --env OBJCOPY=objcopy --executable /lldb-buildbot/lldbSlave/buildWorkingDir/scripts/../build/bin/lldb --channel gdb-remote packets --channel lldb all --skip-category watchpoint --skip-category lldb-mi --results-port 43584 -S fnmac --inferior -p TestDataFormatterLibcxxOptional.py /lldb-buildbot/lldbSlave/buildWorkingDir/llvm/tools/lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional --event-add-entries worker_index=4:int

Configuration: arch=i386 compiler=/usr/bin/clang-3.5
----------------------------------------------------------------------
Collected 4 tests

1: test_with_run_command_dsym (TestDataFormatterLibcxxOptional.LibcxxOptionalDataFormatterTestCase)
   Test that that file and class static variables display correctly. ... skipped 'test case does not fall in any category of interest for this run'
2: test_with_run_command_dwarf (TestDataFormatterLibcxxOptional.LibcxxOptionalDataFormatterTestCase)
   Test that that file and class static variables display correctly. ... 3: test_with_run_command_dwo (TestDataFormatterLibcxxOptional.LibcxxOptionalDataFormatterTestCase)
   Test that that file and class static variables display correctly. ... 4: test_with_run_command_gmodules (TestDataFormatterLibcxxOptional.LibcxxOptionalDataFormatterTestCase)
   Test that that file and class static variables display correctly. ... skipped 'test case does not fall in any category of interest for this run'

======================================================================
ERROR: test_with_run_command_dwarf (TestDataFormatterLibcxxOptional.LibcxxOptionalDataFormatterTestCase)
   Test that that file and class static variables display correctly.
----------------------------------------------------------------------
Error when building test subject.

Build Command:
make VPATH=/lldb-buildbot/lldbSlave/buildWorkingDir/llvm/tools/lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional -C /lldb-buildbot/lldbSlave/buildWorkingDir/scripts/lldb-test-build.noindex/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.test_with_run_command_dwarf -I /lldb-buildbot/lldbSlave/buildWorkingDir/llvm/tools/lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional -f /lldb-buildbot/lldbSlave/buildWorkingDir/llvm/tools/lldb/packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/Makefile MAKE_DSYM=NO ARCH=i386 CC="/usr/bin/clang-3.5" 

Build Command Output:
error: invalid value 'c++17' in '-std=c++17'
error: invalid value 'c++17' in '-std=c++17'
make: *** [main.o] Error 1

[labath]

Thanks for looking out for the bots.

I am afraid the compiler check will not be enough here. After that, you'll run into the issue of the system libc++ not being recent enough to contain std::optional. I suppose this could be handled by including some other header first (to make sure __config is evaluated) and then checking the _LIBCPP_VERSION macro.

I am sorry that this is so annoying. It's surprising that this is the first time we're running into this, but I guess this is the first data formatter for something that hasn't been implemented in libc++ since forever.

[shafik]

Adjust test to filter on clang version and libc++ version to precent build bots from failing due to lack of C++17 or lack of optional support

[shafik]

@davide @labath I believe I have addressed both the C++17 filter and the libc++ filter. Please let me know if you have further comments.

[labath]

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

22

Could you add another line for gcc here? The -std=c++17 flag seems to be supported starting with gcc-5.1.

Also a comment that this is due to the -std flag would be helpful to people looking at this in the future.

45

Replace by self.skipTest(...). This way, the test will be properly marked as skipped.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

16–18

these need to be guarded by the #if too (i'd just move then into the main function).

[shafik]

• Adding comments
• Changing from exit to self.skipTest
• Adding skip for gcc

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

22

Adding a comment makes sense.

So @add_test_categories(["libc++"]) won't skip for gcc bots then?

[shafik]

Fixing gcc skipIf to check for version as well

[labath]

Thanks for the patience. I've tried the patch out on our end. You shouldn't have any problems now.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

22

It won't because it doesn't make sense to do that. Gcc is perfectly capable of using libc++. The only tricky thing is that it doesn't have the magic -stdlib argument, so you have to specify the include paths and libraries explicitly (which our makefiles do).

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

18–21

This could be simplified to bool has_optional = HAVE_OPTIONAL;

[shafik]

Simplifying initialization of has_optional in test.

[shafik]

@labath Addressed comment, thank you for helping out.

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

22

Good point I did not realize this before!

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

18–21

Good catch!

[stella.stamenova]

I see this test failing on Linux right now (bots are down, so I can't confirm that the official bots fail as well). The failure is because of the last decorator which was not part of the review:

@skipIf(macos_version=["<", "10.14"])

It looks like this only works correctly when mac_ver returns a meaningful result (a.k.a. on mac platforms), so linux is broken.

Another thing that I noticed is that the name of the test class (LibcxxOptionalDataFormatterTestCase) was re-used from another test. This has caused problems in the past with test overriding each other's results because they share the same class and test name (as these do).

[shafik]

@stella.stamenova Thank you for catching this. I fixed the test names, I am looking into the best way to fix the skipif now.

[stella.stamenova]

In D49271#1263842, @shafik wrote:

@stella.stamenova Thank you for catching this. I fixed the test names, I am looking into the best way to fix the skipif now.

@shafik I send a change for review this morning that I think should do the trick: https://reviews.llvm.org/D53208. The other option is to change the skipIf to include the os like some of the other ones.

lldb.xcodeproj/project.pbxproj

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packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/Makefile

+LEVEL = ../../../../../make
+
+CXX_SOURCES := main.cpp
+
+USE_LIBCPP := 1
+include $(LEVEL)/Makefile.rules
+CXXFLAGS += -O0
+CXXFLAGS += -std=c++17

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/TestDataFormatterLibcxxOptional.py

+"""
+Test lldb data formatter subsystem.
+"""
+
+from __future__ import print_function
+
+
+import os
+import time
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class LibcxxOptionalDataFormatterTestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @add_test_categories(["libc++"])
+
+    def test_with_run_command(self):
+        """Test that that file and class static variables display correctly."""
+        self.build()
+        self.runCmd("file " + self.getBuildArtifact("a.out"), CURRENT_EXECUTABLE_SET)
+
+        bkpt = self.target().FindBreakpointByID(
+            lldbutil.run_break_set_by_source_regexp(
+                self, "break here"))
+
+        self.runCmd("run", RUN_SUCCEEDED)
+
+        # The stop reason of the thread should be breakpoint.
+        self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+                    substrs=['stopped',
+                             'stop reason = breakpoint'])
+
+        # This is the function to remove the custom formats in order to have a
+        # clean slate for the next test case.
+        def cleanup():
+            self.runCmd('type format clear', check=False)
+            self.runCmd('type summary clear', check=False)
+            self.runCmd('type filter clear', check=False)
+            self.runCmd('type synth clear', check=False)
+            self.runCmd(
+                "settings set target.max-children-count 256",
+                check=False)
+
+        # Execute the cleanup function during test case tear down.
+        self.addTearDownHook(cleanup)
+
+        # empty vectors (and storage pointers SHOULD BOTH BE NULL..)
+        self.expect("frame variable number",
+                    substrs=['engaged=false'])
+
+        lldbutil.continue_to_breakpoint(self.process(), bkpt)
+
+        # first value added
+        self.expect("frame variable number",
+                    substrs=['engaged=true',
+                             '[0] = 42',
+                             '}'])
+
+        # add some more data
+        lldbutil.continue_to_breakpoint(self.process(), bkpt)
+
+        self.expect("frame variable numbers",
+                    substrs=['numbers =  engaged=false'])
+
+        self.expect("p numbers",
+                    substrs=['$0 =  engaged=false'])
+
+        lldbutil.continue_to_breakpoint(self.process(), bkpt)
+
+        self.expect("p numbers",
+                    substrs=['$1 =  engaged=true {',
+                             '[0] = size=4 {',
+                               '[0] = 1',
+                               '[1] = 2',
+                               '[2] = 3',
+                               '[3] = 4',
+                               '}',
+                             '}'])
+
+        # add some more data
+        lldbutil.continue_to_breakpoint(self.process(), bkpt)
+
+        self.expect("frame variable ostring",
+                    substrs=['ostring =  engaged=false'])
+
+        lldbutil.continue_to_breakpoint(self.process(), bkpt)
+
+        self.expect("p ostring",
+                    substrs=['$2 =  engaged=true {',
+                        '[0] = "hello"',
+                        '}'])

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/optional/main.cpp

+#include <cstdio>
+#include <string>
+#include <vector>
+#include <optional>
+
+using int_vect = std::vector<int> ;
+using string_vec = std::vector<std::string> ;
+using optional_int = std::optional<int> ;
+using optional_int_vect = std::optional<int_vect> ;
+using optional_string = std::optional<std::string> ;
+
+int main()
+{
+    optional_int number ;
+
+    printf( "%d\n", number.has_value() ) ; // break here
+
+    number = 42 ;
+
+    printf( "%d\n", *number ) ; // break here
+
+    optional_int_vect numbers ;
+
+    printf( "%d\n", numbers.has_value() ) ; // break here
+
+    numbers = {1,2,3,4} ;
+
+    printf( "%d %d\n", numbers.value()[0], numbers.value()[1] ) ; // break here
+
+    optional_string ostring ;
+
+    printf( "%s\n", ostring.has_value() ) ; // break here
+
+    ostring = "hello" ;
+
+    printf( "%s\n", ostring->c_str() ) ; // break here
+
+    return 0;  // break here
+}

source/Plugins/Language/CPlusPlus/CMakeLists.txt

 add_lldb_library(lldbPluginCPlusPlusLanguage PLUGIN
   BlockPointer.cpp
   CPlusPlusLanguage.cpp
   CPlusPlusNameParser.cpp
   CxxStringTypes.cpp
   LibCxx.cpp
   LibCxxAtomic.cpp
   LibCxxBitset.cpp
   LibCxxInitializerList.cpp
   LibCxxList.cpp
   LibCxxMap.cpp
+  LibCxxOptional.cpp
   LibCxxQueue.cpp
   LibCxxTuple.cpp
   LibCxxUnorderedMap.cpp
   LibCxxVector.cpp
   LibStdcpp.cpp
   LibStdcppTuple.cpp
   LibStdcppUniquePointer.cpp
 
   LINK_LIBS
     lldbCore
     lldbDataFormatters
     lldbHost
     lldbSymbol
     lldbTarget
     lldbUtility
   LINK_COMPONENTS
     Support
 )

source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

std::string CPlusPlusLanguage::MethodName::GetScopeQualifiedName() {
   res += "::";
   res += m_basename;
   return res;
 }
 
 bool CPlusPlusLanguage::IsCPPMangledName(const char *name) {
   // FIXME!! we should really run through all the known C++ Language plugins
   // and ask each one if this is a C++ mangled name
-  
   if (name == nullptr)
     return false;
-  
-  // MSVC style mangling 
+  // MSVC style mangling
   if (name[0] == '?')
     return true;
-  
   return (name[0] != '\0' && name[0] == '_' && name[1] == 'Z');
 }
 
 bool CPlusPlusLanguage::ExtractContextAndIdentifier(
     const char *name, llvm::StringRef &context, llvm::StringRef &identifier) {
   CPlusPlusNameParser parser(name);
   if (auto full_name = parser.ParseAsFullName()) {
     identifier = full_name.getValue().basename;
AddCXXSynthetic(
       ConstString("^std::initializer_list<.+>(( )?&)?$"), stl_synth_flags,
       true);
   AddCXXSynthetic(cpp_category_sp, LibcxxQueueFrontEndCreator,
                   "libc++ std::queue synthetic children",
                   ConstString("^std::__(ndk)?1::queue<.+>(( )?&)?$"),
                   stl_synth_flags, true);
   AddCXXSynthetic(cpp_category_sp, LibcxxTupleFrontEndCreator,
                   "libc++ std::tuple synthetic children",
-                  ConstString("^std::__(ndk)?1::tuple<.*>(( )?&)?$"), stl_synth_flags,
-                  true);
+                  ConstString("^std::__(ndk)?1::tuple<.*>(( )?&)?$"),
+                  stl_synth_flags, true);
+  AddCXXSynthetic(cpp_category_sp, LibcxxOptionalFrontEndCreator,
+                  "libc++ std::optional synthetic children",
+                  ConstString("^std::__(ndk)?1::optional<.+>(( )?&)?$"),
+                  stl_synth_flags, true);
   AddCXXSynthetic(
       cpp_category_sp,
       lldb_private::formatters::LibcxxAtomicSyntheticFrontEndCreator,
       "libc++ std::atomic synthetic children",
       ConstString("^std::__(ndk)?1::atomic<.+>$"), stl_synth_flags, true);
 
   cpp_category_sp->GetRegexTypeSyntheticsContainer()->Add(
       RegularExpressionSP(new RegularExpression(
AddCXXSummary(cpp_category_sp,
                 stl_summary_flags, true);
   AddCXXSummary(
       cpp_category_sp, lldb_private::formatters::LibcxxContainerSummaryProvider,
       "libc++ std::unordered containers summary provider",
       ConstString("^(std::__(ndk)?1::)unordered_(multi)?(map|set)<.+> >$"),
       stl_summary_flags, true);
   AddCXXSummary(cpp_category_sp, LibcxxContainerSummaryProvider,
                 "libc++ std::tuple summary provider",
-                ConstString("^std::__(ndk)?1::tuple<.*>(( )?&)?$"), stl_summary_flags,
-                true);
+                ConstString("^std::__(ndk)?1::tuple<.*>(( )?&)?$"),
+                stl_summary_flags, true);
   AddCXXSummary(
       cpp_category_sp, lldb_private::formatters::LibCxxAtomicSummaryProvider,
       "libc++ std::atomic summary provider",
       ConstString("^std::__(ndk)?1::atomic<.+>$"), stl_summary_flags, true);
+  AddCXXSummary(cpp_category_sp,
+                lldb_private::formatters::LibcxxOptionalSummaryProvider,
+                "libc++ std::optional summary provider",
+                ConstString("^std::__(ndk)?1::optional<.+>(( )?&)?$"),
+                stl_summary_flags, true);
 
   stl_summary_flags.SetSkipPointers(true);
 
   AddCXXSummary(cpp_category_sp,
                 lldb_private::formatters::LibcxxSmartPointerSummaryProvider,
                 "libc++ std::shared_ptr summary provider",
                 ConstString("^std::__(ndk)?1::shared_ptr<.+>(( )?&)?$"),
                 stl_summary_flags, true);

 HardcodedFormatters::HardcodedSyntheticFinder
 CPlusPlusLanguage::GetHardcodedSynthetics() {
   static llvm::once_flag g_initialize;
   static ConstString g_vectortypes("VectorTypes");
   static HardcodedFormatters::HardcodedSyntheticFinder g_formatters;
 
   llvm::call_once(g_initialize, []() -> void {
     g_formatters.push_back([](lldb_private::ValueObject &valobj,
-                              lldb::DynamicValueType,
-                              FormatManager &
-                                  fmt_mgr) -> SyntheticChildren::SharedPointer {
+                              lldb::DynamicValueType, FormatManager &fmt_mgr)
+                               -> SyntheticChildren::SharedPointer {
       static CXXSyntheticChildren::SharedPointer formatter_sp(
           new CXXSyntheticChildren(
               SyntheticChildren::Flags()
                   .SetCascades(true)
                   .SetSkipPointers(true)
                   .SetSkipReferences(true)
                   .SetNonCacheable(true),
               "vector_type synthetic children",
               lldb_private::formatters::VectorTypeSyntheticFrontEndCreator));
       if (valobj.GetCompilerType().IsVectorType(nullptr, nullptr)) {
         if (fmt_mgr.GetCategory(g_vectortypes)->IsEnabled())
           return formatter_sp;
       }
       return nullptr;
     });
     g_formatters.push_back([](lldb_private::ValueObject &valobj,
-                              lldb::DynamicValueType,
-                              FormatManager &
-                                  fmt_mgr) -> SyntheticChildren::SharedPointer {
+                              lldb::DynamicValueType, FormatManager &fmt_mgr)
+                               -> SyntheticChildren::SharedPointer {
       static CXXSyntheticChildren::SharedPointer formatter_sp(
           new CXXSyntheticChildren(
               SyntheticChildren::Flags()
                   .SetCascades(true)
                   .SetSkipPointers(true)
                   .SetSkipReferences(true)
                   .SetNonCacheable(true),
               "block pointer synthetic children",
               lldb_private::formatters::BlockPointerSyntheticFrontEndCreator));
       if (valobj.GetCompilerType().IsBlockPointerType(nullptr)) {
         return formatter_sp;
       }
       return nullptr;
     });
-
   });
 
   return g_formatters;
 }

source/Plugins/Language/CPlusPlus/LibCxx.h

 bool LibcxxStringSummaryProvider(
     ValueObject &valobj, Stream &stream,
     const TypeSummaryOptions &options); // libc++ std::string
 
 bool LibcxxWStringSummaryProvider(
     ValueObject &valobj, Stream &stream,
     const TypeSummaryOptions &options); // libc++ std::wstring
 
+bool LibcxxOptionalSummaryProvider(
+    ValueObject &valobj, Stream &stream,
+    const TypeSummaryOptions &options); // libc++ std::optional<>
+
 bool LibcxxSmartPointerSummaryProvider(
     ValueObject &valobj, Stream &stream,
     const TypeSummaryOptions
         &options); // libc++ std::shared_ptr<> and std::weak_ptr<>
 
 SyntheticChildrenFrontEnd *
 LibcxxVectorBoolSyntheticFrontEndCreator(CXXSyntheticChildren *,
                                          lldb::ValueObjectSP);
SyntheticChildrenFrontEnd *LibcxxFunctionFrontEndCreator(CXXSyntheticChildren *,
                                                          lldb::ValueObjectSP);
 
 SyntheticChildrenFrontEnd *LibcxxQueueFrontEndCreator(CXXSyntheticChildren *,
                                                       lldb::ValueObjectSP);
 
 SyntheticChildrenFrontEnd *LibcxxTupleFrontEndCreator(CXXSyntheticChildren *,
                                                       lldb::ValueObjectSP);
 
+SyntheticChildrenFrontEnd *
+LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
+                              lldb::ValueObjectSP valobj_sp);
+
 } // namespace formatters
 } // namespace lldb_private
 
 #endif // liblldb_LibCxx_h_

source/Plugins/Language/CPlusPlus/LibCxx.cpp

 #include "lldb/Utility/Endian.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/Utility/Stream.h"
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::formatters;
 
+bool lldb_private::formatters::LibcxxOptionalSummaryProvider(
+    ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
+  ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
+  if (!valobj_sp)
+    return false;
+
+  ValueObjectSP engaged_sp(
+      valobj_sp->GetChildMemberWithName(ConstString("__engaged_"), true));
+
+  if (!engaged_sp)
+    return false;
+
+  llvm::StringRef engaged_as_cstring(
+      engaged_sp->GetValueAsUnsigned(0) == 1 ? "true" : "false");
+
+  stream.Printf(" engaged=%s ", engaged_as_cstring.data());
+
+  return true;
+}
+
 bool lldb_private::formatters::LibcxxSmartPointerSummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
   ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
   if (!valobj_sp)
     return false;
   ValueObjectSP ptr_sp(
       valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true));
   ValueObjectSP count_sp(valobj_sp->GetChildAtNamePath(
bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
 
   TargetSP target_sp(valobj_sp->GetTargetSP());
 
   if (!target_sp)
     return false;
 
   if (!valobj_sp)
     return false;
-  
   static ConstString g___i_("__i_");
-  
   // this must be a ValueObject* because it is a child of the ValueObject we
   // are producing children for it if were a ValueObjectSP, we would end up
   // with a loop (iterator -> synthetic -> child -> parent == iterator) and
   // that would in turn leak memory by never allowing the ValueObjects to die
   // and free their memory
   m_pair_ptr = valobj_sp
                    ->GetValueForExpressionPath(
                        ".__i_.__ptr_->__value_", nullptr, nullptr,
m_pair_ptr = valobj_sp
                          nullptr)
                      .get();
     if (m_pair_ptr) {
       auto __i_(valobj_sp->GetChildMemberWithName(g___i_, true));
       if (!__i_) {
         m_pair_ptr = nullptr;
         return false;
       }
-      CompilerType pair_type(__i_->GetCompilerType().GetTypeTemplateArgument(0));
-      std::string name; uint64_t bit_offset_ptr; uint32_t bitfield_bit_size_ptr; bool is_bitfield_ptr;
-      pair_type = pair_type.GetFieldAtIndex(0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
+      CompilerType pair_type(
+          __i_->GetCompilerType().GetTypeTemplateArgument(0));
+      std::string name;
+      uint64_t bit_offset_ptr;
+      uint32_t bitfield_bit_size_ptr;
+      bool is_bitfield_ptr;
+      pair_type = pair_type.GetFieldAtIndex(
+          0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
       if (!pair_type) {
         m_pair_ptr = nullptr;
         return false;
       }
-      
       auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
       m_pair_ptr = nullptr;
-      if (addr && addr!=LLDB_INVALID_ADDRESS) {
-        ClangASTContext *ast_ctx = llvm::dyn_cast_or_null<ClangASTContext>(pair_type.GetTypeSystem());
+      if (addr && addr != LLDB_INVALID_ADDRESS) {
+        ClangASTContext *ast_ctx =
+            llvm::dyn_cast_or_null<ClangASTContext>(pair_type.GetTypeSystem());
         if (!ast_ctx)
           return false;
-        CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(ConstString(), {
-          {"ptr0",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"ptr1",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"ptr2",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"cw",ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
-          {"payload",pair_type}
-        });
-        DataBufferSP buffer_sp(new DataBufferHeap(tree_node_type.GetByteSize(nullptr),0));
+        CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
+            ConstString(),
+            {{"ptr0",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"ptr1",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"ptr2",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
+             {"payload", pair_type}});
+        DataBufferSP buffer_sp(
+            new DataBufferHeap(tree_node_type.GetByteSize(nullptr), 0));
         ProcessSP process_sp(target_sp->GetProcessSP());
         Status error;
-        process_sp->ReadMemory(addr, buffer_sp->GetBytes(), buffer_sp->GetByteSize(), error);
+        process_sp->ReadMemory(addr, buffer_sp->GetBytes(),
+                               buffer_sp->GetByteSize(), error);
         if (error.Fail())
           return false;
-        DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(), process_sp->GetAddressByteSize());
-        auto pair_sp = CreateValueObjectFromData("pair", extractor, valobj_sp->GetExecutionContextRef(), tree_node_type);
+        DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(),
+                                process_sp->GetAddressByteSize());
+        auto pair_sp = CreateValueObjectFromData(
+            "pair", extractor, valobj_sp->GetExecutionContextRef(),
+            tree_node_type);
         if (pair_sp)
-          m_pair_sp = pair_sp->GetChildAtIndex(4,true);
+          m_pair_sp = pair_sp->GetChildAtIndex(4, true);
       }
     }
   }
 
   return false;
 }
 
 size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::

 static bool ExtractLibcxxStringInfo(ValueObject &valobj,
                                     ValueObjectSP &location_sp,
                                     uint64_t &size) {
   ValueObjectSP D(valobj.GetChildAtIndexPath({0, 0, 0, 0}));
   if (!D)
     return false;
 
   ValueObjectSP layout_decider(
       D->GetChildAtIndexPath(llvm::ArrayRef<size_t>({0, 0})));
 
   // this child should exist
   if (!layout_decider)
     return false;
 
   ConstString g_data_name("__data_");
   ConstString g_size_name("__size_");
   bool short_mode = false; // this means the string is in short-mode and the

source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp

+//===-- LibCxxOptional.cpp --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LibCxx.h"
+#include "lldb/DataFormatters/FormattersHelpers.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+namespace {
+
+class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  OptionalFrontEnd(ValueObject &valobj) : SyntheticChildrenFrontEnd(valobj) {
+    Update();
+  }
+
+  size_t GetIndexOfChildWithName(const ConstString &name) override {
+    return formatters::ExtractIndexFromString(name.GetCString());
+  }
+
+  bool MightHaveChildren() override { return true; }
+  bool Update() override;
+  size_t CalculateNumChildren() override { return m_size; }
+  ValueObjectSP GetChildAtIndex(size_t idx) override;
+
+private:
+  size_t m_size = 0;
+  ValueObjectSP m_base_sp;
+};
+} // namespace
+
+bool OptionalFrontEnd::Update() {
+  ValueObjectSP engaged_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
+
+  if (!engaged_sp)
+    return false;
+
+  m_size = engaged_sp->GetValueAsSigned(0);
+
+  return false;
+}
+
+ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
+  if (idx >= m_size)
+    return ValueObjectSP();
+
+  ValueObjectSP val_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
+          ->GetParent()
+          ->GetChildAtIndex(0, true)
+          ->GetChildMemberWithName(ConstString("__val_"), true));
+
+  if (!val_sp)
+    return ValueObjectSP();
+
+  CompilerType holder_type = val_sp->GetCompilerType();
+
+  if (!holder_type)
+    return ValueObjectSP();
+
+  return val_sp->Clone(ConstString(llvm::formatv("Value").str()));
+}
+
+SyntheticChildrenFrontEnd *
+formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
+                                          lldb::ValueObjectSP valobj_sp) {
+  if (valobj_sp)
+    return new OptionalFrontEnd(*valobj_sp);
+  return nullptr;
+}