IntelliSense crashing when hovering over certain C++ types of data.

[conkerkh]

Environment

• OS and Version: checked on Ubuntu 23 and MacOS
• VS Code Version: 1.83.0
• C/C++ Extension Version: 1.17.5
• If using SSH remote, specify OS of remote machine:

Bug Summary and Steps to Reproduce

Bug Summary:
cpptools-srv is crashing in some C++ files, looking at the stack trace of a crashing thread it might have something to do with templates but I'm not sure. It's impossible to hover over some types of data in C++ sources (hovering over them will crash cpptools-srv)

Steps to reproduce:
Hover over anything in a C++ source that doesn't get parsed correctly by cpptools-srv

Expected behavior:
Get a usual Intellisense prompt

Configuration and Logs

c_cpp_properties.json contains path to g++ executable and path to compile_commands.json file, C files and some C++ files are working correctly so configuration is unlikely not an issue

"cpptools-srv" received signal SIGSEGV, Segmentation fault.

set_node_operator(an_expr_node*, an_expr_operator_kind, a_type*, int, an_expr_node*) (Unknown Source:0)
make_operator_node(an_expr_operator_kind, a_type*, an_expr_node*) (Unknown Source:0)
build_binary_result_operand_full(an_operand*, an_operand*, an_expr_operator_kind, a_type*, int, an_operand*) (Unknown Source:0)
do_binary_operation_full(an_expr_operator_kind, an_operand*, an_operand*, a_type*, int, an_operand*, a_source_position*, unsigned int, a_source_position*) (Unknown Source:0)
scan_subscript_operator(an_operand*, int, a_rescan_control_block*, an_operand*) (Unknown Source:0)
scan_expr_full(an_operand*, an_operand*, int, int) (Unknown Source:0)
scan_void_expression(int, int, int, a_dynamic_init**, an_init_component*) (Unknown Source:0)
expression_statement(int) (Unknown Source:0)
statement(int, int) (Unknown Source:0)
compound_statement_full(int, int, int, int, int, a_type**) (Unknown Source:0)
statement(int, int) (Unknown Source:0)
if_statement() (Unknown Source:0)
statement(int, int) (Unknown Source:0)
compound_statement_full(int, int, int, int, int, a_type**) (Unknown Source:0)
scan_function_body(a_routine*, a_func_info_block*, unsigned long, a_macro_arg_fixup**, a_macro_arg_fixup**) (Unknown Source:0)
function_prototype_instantiation(a_symbol*) (Unknown Source:0)
process_deferred_class_fixups(int) (Unknown Source:0)
process_deferred_class_fixups_and_instantiations(int) (Unknown Source:0)
template_declaration(a_tmpl_decl_state*, int*) [clone .constprop.0] (Unknown Source:0)
template_or_specialization_declaration_full(a_tmpl_decl_state*, int, a_decl_parse_state*) (Unknown Source:0)
template_or_specialization_declaration(a_token_kind*, int, a_source_position*, int, a_decl_parse_state*) (Unknown Source:0)
template_directive_or_declaration(a_token_kind*, int, a_source_position*) (Unknown Source:0)
scan_nonmember_declaration(a_decl_parse_state*, a_source_range*) (Unknown Source:0)
declaration(int, int, int, int, a_param_id*, a_source_range*, a_decl_parse_state*) [clone .constprop.0] (Unknown Source:0)
namespace_declaration(a_token_kind*, int, int, a_source_position*, a_symbol**) (Unknown Source:0)
namespace_declaration(a_token_kind*, int, int, a_source_position*, a_symbol**) (Unknown Source:0)
scan_nonmember_declaration(a_decl_parse_state*, a_source_range*) (Unknown Source:0)
declaration(int, int, int, int, a_param_id*, a_source_range*, a_decl_parse_state*) [clone .constprop.0] (Unknown Source:0)
translation_unit() (Unknown Source:0)
process_translation_unit(char const*, int, an_exported_template_file*) (Unknown Source:0)
cfe_main(int, char**) (Unknown Source:0)
cfe_main_exception_handler(int, char**) (Unknown Source:0)
edg_main(int, char**) (Unknown Source:0)
invoke_edge_compiler(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&) (Unknown Source:0)
edge_compiler_main(int, char const**) (Unknown Source:0)
a_compiler_thread::compiler_thread_routine(a_compiler_thread*) (Unknown Source:0)
msvc::thread_helper_t::thread_entry(void*) (Unknown Source:0)
start (Unknown Source:0)
[Unknown/Just-In-Time compiled code] (Unknown Source:0)

cpptools gracefully exits/restarts so it's related to cpptools-srv

IntelliSense process crash detected.
IntelliSense process crash detected.
IntelliSense process crash detected.
IntelliSense process crash detected.
IntelliSense process crash detected.
IntelliSense process crash detected.
IntelliSense process crash detected.

Other Extensions

No response

Additional context

No response

[Colengms]

Hi @conkerkh . Thanks for letting us know. Could isolate the issue into a code example that reproduces the problem, which we could use to investigate further?

[conkerkh]

I would be happy to help here, however I can't easily reproduce this problem. It's crashing only in one of my projects, and I have no clue how to find out which header is causing this issue. If you have any suggestion how to get information from gdb where exactly it fails I could try to write a sample code that reproduces the problem. Debug info from C/C++ plugin doesn't say much

[Colengms]

Hi @conkerkh . The crash would be related to code in the file open at the time, or one of the headers it includes, and possibly related to what is being hovered over.

I'd suggest temporarily reducing the source file to only a small bit of code. If the issue repro's, start removing unused headers. Alternatively, you might try generating a preprocessed file (i.e. using the -E argument to g++). If the issue occurs within that file, reducing it would involve stripping out code from the end until the repro is removed, then putting that code back and removing code prior to it that's unrelated. Generally, this process should result in just the specific syntax triggering the issue. Or, if you can reduce a preprocessed file enough that you're comfortable sharing its contents, we could reduce it further.

[conkerkh]

I managed to reproduce it with this piece of code:

#include <cstdint>

namespace Test
{
    typedef void (*error_callback)();

    template <uint32_t T>
    class SomeClass {
    private:
        static error_callback _cb;

    public:
        void Something()
        {
            if (T == 0x2000) {
                _cb[0] = nullptr;
            }
        }
    };
};   

int main()
{
    return 0;
}

This code has some mistakes.
If you look at it, _cb[0] doesn't make much sense, and should be marked as an error. Instead, I believe it is the main reason why the cpptools-srv crashes.

It may be possible that the if statement inside "Something" doesn't make a difference.

[Colengms]

Hi @conkerkh . Thanks for the reduced code. Unfortunately, I'm not able to reproduce a crash with this code, with 1.17.5 of the C/C++ Extension, on either Ubuntu (w/clang-16) or on macOS. If you create a fresh folder and move this code into it, does the crash still repro for you? Is there anything else (other than hovering over the various identifiers) that you are doing that may be necessary to repro the crash? It's possible there may be some details about your configuration, or C_Cpp related settings, that I may need to set as well to repro. Can you provide that information as well?

[conkerkh]

I used GCC compilers, so if you select g++ for compilerPath in c_cpp_properties.json file it should work with this example. Looks like clang will mark the line with _cb[0] as an error.

For this example:

    "configurations": [
        {
            "name": "Test",
            "compilerPath": "/usr/local/bin/g++-13",
            "cStandard": "c11",
            "cppStandard": "c++17",
            "intelliSenseMode": "linux-gcc-x86",
            "compileCommands": "${workspaceFolder}/build/compile_commands.json",
            "defines": [],
        }
    ],
    "version": 4
}```

[Colengms]

Hi @conkerkh . Thanks for the clarification. I can reproduce the crash when using a GGC intelliSense mode on Linux. We will investigate further.

[sean-mcmanus]

Fixed with https://github.com/microsoft/vscode-cpptools/releases/tag/v1.18.2