IntelliSense process crash when aliasing std::tuple #14098
Description
Environment
- C/C++ Extension Version: 1.29.2
Bug Summary and Steps to Reproduce
The following will crash the language server.
#include <tuple>
template<typename... T> using tup = std::tuple<T...>;
auto crashed(){
return tup{5};
}Results in: IntelliSense process crash detected: handle_initialize
You can also write
void crashed(){
auto x = tup{5};
}To receive IntelliSense process crash detected: handle_update_intellisense
However, the following will not crash it.
void ok(){
tup<int> x = {5};
}Configuration and Logs
Log Diagnostics:
-------- Diagnostics - 12/10/2025, 12:43:44 AM
Version: 1.29.2
Current Configuration:
{
"name": "Win32",
"includePath": [
"b:/Documents/Code/ReproducibleIntellisenseCrash/**"
],
"defines": [
"_DEBUG",
"UNICODE",
"_UNICODE"
],
"windowsSdkVersion": "10.0.22621.0",
"cStandard": "gnu23",
"cppStandard": "c++26",
"intelliSenseMode": "windows-gcc-x64",
"intelliSenseModeIsExplicit": true,
"cStandardIsExplicit": true,
"cppStandardIsExplicit": true,
"mergeConfigurations": false,
"recursiveIncludes": {},
"recursiveIncludesReduceIsExplicit": false,
"recursiveIncludesPriorityIsExplicit": false,
"recursiveIncludesOrderIsExplicit": false,
"compilerPath": "C:\\msys64\\ucrt64\\bin\\gcc.exe",
"compilerPathIsExplicit": true,
"browse": {
"limitSymbolsToIncludedHeaders": true
}
}
Modified Settings:
{
"C_Cpp.default.intelliSenseMode": "windows-gcc-x64",
"C_Cpp.default.compilerPath": "C:\\msys64\\ucrt64\\bin\\gcc.exe",
"C_Cpp.default.cStandard": "gnu23",
"C_Cpp.default.cppStandard": "c++26",
"C_Cpp.clang_format_style": "file:A:/Coding/.clang-format",
"C_Cpp.clang_format_fallbackStyle": "WebKit",
"C_Cpp.loggingLevel": "Debug"
}
Additional Tracked Settings:
{
"editorTabSize": 4,
"editorInsertSpaces": true,
"editorAutoClosingBrackets": "languageDefined",
"filesEncoding": "utf8",
"filesAssociations": {
"*.asm": "arm",
"*.atsln": "sln",
"*.f": "glsl",
"*.fsh": "glsl",
"*.inc": "arm",
"*.ipp": "cpp",
"*.js.download": "javascript",
"*.Rmd": "markdown",
"*.s": "arm",
"*.sasmproj": "toml",
"*.tpp": "cpp",
"*.v": "glsl",
"*.vsh": "glsl"
},
"filesExclude": {
"**/.git": false,
"**/.svn": true,
"**/.hg": true,
"**/.DS_Store": true,
"**/Thumbs.db": true,
"**/.acpmeta": true,
"**/CVS": true
},
"filesAutoSaveAfterDelay": false,
"editorInlayHintsEnabled": true,
"editorParameterHintsEnabled": true,
"searchExclude": {
"**/node_modules": true,
"**/bower_components": true,
"**/*.code-search": true
},
"workbenchSettingsEditor": "ui"
}
cpptools version (native): 1.29.2.0
Current database path: C:\USERS\_____\APPDATA\LOCAL\MICROSOFT\VSCODE-CPPTOOLS\AE7C2A44E0E3386F3C69C9A14F8F4682\.BROWSE.VC.DB
No active translation units.
------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 14353
Number of files parsed: 2419
Call stack of "compiler_thread_routine":
--------------------------
cpptools-srv.exe!copy_pack_expansion_descr_with_substitution() (Unknown Source:0)
cpptools-srv.exe!copy_template_arg_list_with_substitution(struct a_symbol *,struct a_template_arg *,struct a_template_param *,struct a_template_param *,struct a_template_arg *,struct a_template_param *,struct a_source_position *,int,int *,struct a_ctws_state *) (Unknown Source:0)
cpptools-srv.exe!copy_template_class_reference_with_substitution() (Unknown Source:0)
cpptools-srv.exe!copy_type_with_substitution(struct a_type *,struct a_template_arg *,struct a_template_param *,struct a_source_position *,int,int *,struct a_ctws_state *) (Unknown Source:0)
cpptools-srv.exe!copy_parent_type_with_substitution(struct a_symbol *,struct a_type *,struct a_template_arg *,struct a_template_param *,struct a_source_position *,int,struct a_type * *,int,int *,struct a_ctws_state *) (Unknown Source:0)
cpptools-srv.exe!symbol_for_template_param_unknown_entity_con_after_substitution(struct a_constant *,struct a_template_arg *,struct a_template_param *,struct a_source_position *,struct a_ctws_state *,int) (Unknown Source:0)
cpptools-srv.exe!make_operand_for_rescanned_identifier() (Unknown Source:0)
cpptools-srv.exe!rescan_expr_with_substitution_internal(struct an_expr_node *,struct a_rescan_control_block *,int,struct an_operand *,struct an_operand *,int) (Unknown Source:0)
cpptools-srv.exe!make_rescan_operand_full(struct an_expr_node *,struct a_rescan_control_block *,int,struct an_operand *,struct an_operand *) (Unknown Source:0)
cpptools-srv.exe!scan_function_call() (Unknown Source:0)
cpptools-srv.exe!rescan_expr_with_substitution_internal(struct an_expr_node *,struct a_rescan_control_block *,int,struct an_operand *,struct an_operand *,int) (Unknown Source:0)
cpptools-srv.exe!rescan_expr_with_substitution(struct an_expr_node *,struct a_type *,struct a_rescan_control_block *,struct a_constant *) (Unknown Source:0)
cpptools-srv.exe!copy_template_param_expr(struct an_expr_node *,struct a_template_arg *,struct a_template_param *,struct a_type *,struct a_source_position *,int,int *,struct a_ctws_state *,struct a_constant *,struct a_constant * *) (Unknown Source:0)
cpptools-srv.exe!create_transformed_deduction_guide_for_alias_template(struct a_symbol *,struct a_symbol *) (Unknown Source:0)
cpptools-srv.exe!create_deduction_guides_for_alias_template() (Unknown Source:0)
cpptools-srv.exe!update_implicit_deduction_guides(struct a_symbol *) (Unknown Source:0)
cpptools-srv.exe!deduce_class_template_args(struct a_type *,int,int,int,struct an_init_component *,struct a_source_position *,struct a_type * *,int *) (Unknown Source:0)
cpptools-srv.exe!deduce_placeholder_type() (Unknown Source:0)
cpptools-srv.exe!prescan_initializer_for_auto_type_deduction(struct a_decl_parse_state *,int) (Unknown Source:0)
cpptools-srv.exe!scan_functional_notation_type_conversion() (Unknown Source:0)Additional context
I've prepared a minimal reproducable example attached here for use with CMake-Tools providing the intellisense configuration. All compilers I've tested resulted in a crash (msvc-17.14.19, gcc15-msys2-ucrt, clang21-msys2-ucrt)