Frequent IntelliSense crash on macOS

[jryans]

Type: LanguageService

Describe the bug

• OS and Version: macOS 10.14.6
• VS Code Version: 1.38.1
• C/C++ Extension Version: 0.25.1

IntelliSense indexing seems to crash regularly for me. Here's an example stack trace:

Stack trace

0   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100295a5b add_symbol_to_overload_list + 539
1   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100295e8b enter_overloaded_symbol + 267
2   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100059ed5 decl_member_function_template + 469
3   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100057b32 class_member_declaration + 13362
4   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005c27b class_member_template_declaration + 123
5   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002d1800 template_declaration + 6608
6   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002c361f template_or_specialization_declaration + 5183
7   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002c212e template_directive_or_declaration + 910
8   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005db89 scan_class_definition + 5177
9   Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002a9cf5 f_instantiate_template_class_full + 3669
10  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001001399d0 cast_type_pre_check + 80
11  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010011e96c scan_functional_notation_type_conversion + 1116
12  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100112062 scan_identifier + 2930
13  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001001018cb scan_expr_full + 1787
14  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100106e0d scan_decltype_operator + 685
15  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001001f17d9 f_is_generalized_identifier_start + 1753
16  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000e7d06 decl_specifiers + 3846
17  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000bee16 type_name_full + 214
18  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000a95c5 function_declarator + 13765
19  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000ae4cd r_declarator + 8237
20  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000a998c declarator + 492
21  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100055cd4 class_member_declaration + 5588
22  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005c27b class_member_template_declaration + 123
23  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002d1800 template_declaration + 6608
24  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002c361f template_or_specialization_declaration + 5183
25  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002c212e template_directive_or_declaration + 910
26  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005db89 scan_class_definition + 5177
27  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002a9cf5 f_instantiate_template_class_full + 3669
28  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005f6d0 scan_base_specifier_list + 2736
29  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005d0da scan_class_definition + 2442
30  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010020d3e6 get_definition_of_class + 918
31  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002a92d5 f_instantiate_template_class_full + 1077
32  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005f6d0 scan_base_specifier_list + 2736
33  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005d0da scan_class_definition + 2442
34  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000e0ae2 class_specifier + 14834
35  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000e727f decl_specifiers + 1151
36  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100054c47 class_member_declaration + 1351
37  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010005db11 scan_class_definition + 5057
38  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010020d3e6 get_definition_of_class + 918
39  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002a92d5 f_instantiate_template_class_full + 1077
40  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001001202f7 scan_dynamic_cast_operator + 967
41  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010010413d scan_expr_full + 12141
42  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010010e50d scan_expr_as_init_component + 205
43  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000fb5a6 prescan_initializer_for_auto_type_deduction + 518
44  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000d13ff initializer + 2623
45  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000c924b scan_nonmember_declaration + 17979
46  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100289060 decl_statement + 272
47  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002865e1 statement + 8305
48  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100283a39 compound_statement_full + 825
49  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100177b76 scan_function_body + 4790
50  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010017acc1 function_definition + 4385
51  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000c871b scan_nonmember_declaration + 15115
52  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001000ca660 declaration + 256
53  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010034d088 compile_fragment((anonymous namespace)::a_fragment_buffer const&, a_canonicalized_file_name, unsigned long, unsigned long, unsigned long, bool, a_declaration_context const&, a_region_scope_info const&, std::__1::vector, std::__1::allocator >, std::__1::allocator, std::__1::allocator > > > const&, bool, bool, bool, bool*) + 2664
54  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010034ae2b before_tu_wrapup + 571
55  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002e5608 process_translation_unit + 760
56  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100041bf9 cfe_main + 121
57  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100309bb9 cfe_main_exception_handler + 9
58  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100041cf9 edg_main + 9
59  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002ff88b invoke_edge_compiler(std::__1::vector, std::__1::allocator >, std::__1::allocator, std::__1::allocator > > >&) + 9595
60  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x00000001002fd1f9 edge_compiler_main(int, char const**) + 105
61  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010034b3d3 preparse(int, char const**, a_scout_store*, edge::translation_unit*) + 227
62  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x0000000100317f29 a_compiler_thread::compiler_thread_routine(a_compiler_thread*) + 89
63  Microsoft.VSCode.CPP.IntelliSense.Msvc.darwin	0x000000010034308c void* std::__1::__thread_proxy >, void (*)(a_compiler_thread*), a_compiler_thread*> >(void*) + 44
64  libsystem_pthread.dylib       	0x00007fff5ca412eb _pthread_body + 126
65  libsystem_pthread.dylib       	0x00007fff5ca44249 _pthread_start + 66
66  libsystem_pthread.dylib       	0x00007fff5ca4040d thread_start + 13

To Reproduce
This seems to happen across a variety of projects, but to reproduce what I was doing just now:

1. Clone https://github.com/stephenrkell/liballocs
2. Check out submodules with git submodule update --init --recursive
3. Open the file tools/dumptypes.cpp
4. Hover near line 67:

static string typename_for_vaddr_interval(iterator_df<subprogram_die> i_subp,
	const boost::icl::discrete_interval<Dwarf_Off> interval);

5. You should see an IntelliSense crash within ~5 seconds

Expected behavior
I expect IntelliSense to work without crashing.

Screenshots

Additional context

• No per-project C++ settings / c_cpp_properties.json in use
• All C++ extension settings at default, except for:

  "C_Cpp.dimInactiveRegions": false,
  "C_Cpp.clang_format_fallbackStyle": "Mozilla",

[sean-mcmanus]

I got the bug to repro with VS. It's caused by clang's std::pair causing our parser to crash when the 2nd template argument isn't a complete type (other repros of the crash may also be possible). I've filed a VS bug: https://developercommunity.visualstudio.com/content/problem/752637/cc-intellisense-crashes-when-parsing-clangs-stdpai.html