Empty `flags` list crashes server with no explanation

[Svalorzen]

Issue Prelude

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the brackets) before filing your issue:

• I have read and understood YCM's [CONTRIBUTING][cont] document.
• I have read and understood YCM's [CODE_OF_CONDUCT][code] document.
• I have read and understood YCM's [README][readme], especially the
  [Frequently Asked Questions][faq] section.
• I have searched YCM's issue tracker to find issues similar to the one I'm
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• If filing a bug report, I have included the output of vim --version.
• If filing a bug report, I have included the output of :YcmDebugInfo.
• If filing a bug report, I have attached the contents of the logfiles using
  the :YcmToggleLogs command.
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  version) I am using.
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  my issue, using vim -Nu /path/to/YCM/vimrc_ycm_minimal, including what I
  expected to happen and what actually happened.
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  of install.py (or cmake/make/ninja) including its invocation
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Issue Details

Provide a clear description of the problem, including the following key
questions:

In a maybe misconfigured .ycm_extra_conf.py, YCM reports that Server is initializing, even though actually the server crashed and clangd closed in response to a failed pipe.

• What did you do?

Include steps to reproduce here.

Have something like:

def Settings(**kwargs):
    return {
        'flags': [],
        'compilation_database_folder': 'build'
    }

as .ycm_extra_conf.py. The empty flags is the important part (removing it solves the problem).

• What did you expect to happen?

If that configuration value was not acceptable, server should have just told me to either remove it or add at least one flag.

• What actually happened?

Any code interaction with YCM replies that the server is initializing. :YcmDebugInfo reports that clangd is not running, as well as the server is dead.

Diagnostic data

Output of vim --version

VIM - Vi IMproved 9.1 (2024 Jan 02, compiled Sep 05 2025 19:44:46)
Included patches: 1-16, 647, 678, 697
Modified by team+vim@tracker.debian.org
Compiled by team+vim@tracker.debian.org
Huge version with GTK3 GUI.  Features included (+) or not (-):
+acl               +file_in_path      +mouse_urxvt       -tag_any_white
+arabic            +find_in_path      +mouse_xterm       +tcl
+autocmd           +float             +multi_byte        +termguicolors
+autochdir         +folding           +multi_lang        +terminal
-autoservername    -footer            -mzscheme          +terminfo
+balloon_eval      +fork()            +netbeans_intg     +termresponse
+balloon_eval_term +gettext           +num64             +textobjects
+browse            -hangul_input      +packages          +textprop
++builtin_terms    +iconv             +path_extra        +timers
+byte_offset       +insert_expand     +perl              +title
+channel           +ipv6              +persistent_undo   +toolbar
+cindent           +job               +popupwin          +user_commands
+clientserver      +jumplist          +postscript        +vartabs
+clipboard         +keymap            +printer           +vertsplit
+cmdline_compl     +lambda            +profile           +vim9script
+cmdline_hist      +langmap           -python            +viminfo
+cmdline_info      +libcall           +python3           +virtualedit
+comments          +linebreak         +quickfix          +visual
+conceal           +lispindent        +reltime           +visualextra
+cryptv            +listcmds          +rightleft         +vreplace
+cscope            +localmap          +ruby              +wildignore
+cursorbind        +lua               +scrollbind        +wildmenu
+cursorshape       +menu              +signs             +windows
+dialog_con_gui    +mksession         +smartindent       +writebackup
+diff              +modify_fname      +sodium            +X11
+digraphs          +mouse             +sound             +xattr
+dnd               +mouseshape        +spell             -xfontset
-ebcdic            +mouse_dec         +startuptime       +xim
+emacs_tags        +mouse_gpm         +statusline        -xpm
+eval              -mouse_jsbterm     -sun_workshop      +xsmp_interact
+ex_extra          +mouse_netterm     +syntax            +xterm_clipboard
+extra_search      +mouse_sgr         +tag_binary        -xterm_save
-farsi             -mouse_sysmouse    -tag_old_static    
   system vimrc file: "/etc/vim/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "/etc/vim/gvimrc"
    user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
    system menu file: "$VIMRUNTIME/menu.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK -I/usr/include/gtk-3.0 -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/libmount -I/usr/include/blkid -I/usr/include/fribidi -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/x86_64-linux-gnu -I/usr/include/webp -I/usr/include/gio-unix-2.0 -I/usr/include/atk-1.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/at-spi-2.0 -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -pthread -Wdate-time -g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/build/vim-xEtJBd/vim-9.1.0016=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/build/vim-xEtJBd/vim-9.1.0016=/usr/src/vim-2:9.1.0016-1ubuntu7.9 -DSYS_VIMRC_FILE=\"/etc/vim/vimrc\" -DSYS_GVIMRC_FILE=\"/etc/vim/gvimrc\" -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 
Linking: gcc -Wl,-E -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro -Wl,-z,now -Wl,--as-needed -o vim -lgtk-3 -lgdk-3 -lz -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -latk-1.0 -lcairo-gobject -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lSM -lICE -lXt -lX11 -lXdmcp -lSM -lICE -lm -ltinfo -lselinux -lcanberra -lsodium -lacl -lattr -lgpm -L/usr/lib -llua5.1 -Wl,-E -fstack-protector-strong -L/usr/local/lib -L/usr/lib/x86_64-linux-gnu/perl/5.38/CORE -lperl -ldl -lm -lpthread -lcrypt -L/usr/lib/python3.12/config-3.12-x86_64-linux-gnu -lpython3.12 -ldl -lm -L/usr/lib/x86_64-linux-gnu -ltcl8.6 -ldl -lz -lpthread -lm -lruby-3.2 -lm -lpthread -L/usr/lib 

Output of YcmDebugInfo

Printing YouCompleteMe debug information...
-- Resolve completions: Never
-- Client logfile: /tmp/ycm_546smr6j.log
-- Server Python interpreter: /usr/bin/python3
-- Server Python version: 3.12.3
-- Server has Clang support compiled in: True
-- Clang version: clang version 21.1.3 (https://github.com/ycm-core/llvm 6d06e83ae7dcd53babc43b60d3c6e998b4606314)
-- Extra configuration file found and loaded
-- Extra configuration path: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin/.ycm_extra_conf.py
-- C-family completer debug information:
--   Clangd not running
--   Clangd executable: ['/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd', '--header-insertion=never', '-header-insertion-decorators=0', '-resource-dir=/home/svalorzen/.vim/bundle/YouCompl
eteMe/third_party/ycmd/third_party/clang/lib/clang/21.1.3', '-limit-results=500']
--   Clangd logfiles:
--     /tmp/clangd_stderr8cy11e9e.log
--   Clangd Server State: Dead
--   Clangd Project Directory: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin
--   Clangd Open Workspaces: {'/home/svalorzen/Projects/SoundRadix/AddSynth/plugin'}
--   Clangd Settings: {}
--   Clangd Compilation Command: False
-- Server running at: http://127.0.0.1:38627
-- Server process ID: 24347
-- Server logfiles:
--   /tmp/ycmd_38627_stdout_jox3q57e.log
--   /tmp/ycmd_38627_stderr_whunlpau.log
-- Semantic highlighting supported: True
-- Virtual text supported: True
-- Popup windows supported: True

Server error logfile

The problem is likely the second set of errors, where there is an IndexError.

2025-11-27 10:29:13,109 - INFO - Completion config: 50, detailing 0 candiates
2025-11-27 10:29:13,109 - INFO - Completion config: 50, detailing 0 candiates
2025-11-27 10:29:13,109 - INFO - Completion config: 50, detailing 0 candiates
2025-11-27 10:29:13,109 - INFO - Completion config: 50, detailing 0 candiates
127.0.0.1 - - [27/Nov/2025 10:29:13] "GET /ready HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:29:13] "GET /signature_help_available?subserver=gitignore HTTP/1.1" 200 18
2025-11-27 10:29:13,212 - ERROR - Semantic completion not available for ['gitignore']
Traceback (most recent call last):
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 111, in FiletypeCompletionAvailable
    self.GetFiletypeCompleter( filetypes )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 96, in GetFiletypeCompleter
    raise ValueError(
ValueError: No semantic completer exists for filetypes: ['gitignore']
2025-11-27 10:29:13,216 - INFO - Adding buffer identifiers for file: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin/.gitignore
127.0.0.1 - - [27/Nov/2025 10:29:13] "POST /event_notification HTTP/1.1" 200 2
127.0.0.1 - - [27/Nov/2025 10:29:13] "POST /receive_messages HTTP/1.1" 200 5
2025-11-27 10:29:13,286 - ERROR - Semantic completion not available for ['gitignore']
Traceback (most recent call last):
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 111, in FiletypeCompletionAvailable
    self.GetFiletypeCompleter( filetypes )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 96, in GetFiletypeCompleter
    raise ValueError(
ValueError: No semantic completer exists for filetypes: ['gitignore']
127.0.0.1 - - [27/Nov/2025 10:29:13] "POST /event_notification HTTP/1.1" 200 2
2025-11-27 10:29:13,314 - ERROR - Semantic completion not available for ['gitignore']
Traceback (most recent call last):
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 111, in FiletypeCompletionAvailable
    self.GetFiletypeCompleter( filetypes )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 96, in GetFiletypeCompleter
    raise ValueError(
ValueError: No semantic completer exists for filetypes: ['gitignore']
127.0.0.1 - - [27/Nov/2025 10:29:13] "POST /semantic_completion_available HTTP/1.1" 200 5
2025-11-27 10:29:16,786 - ERROR - Semantic completion not available for ['gitignore']
Traceback (most recent call last):
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 111, in FiletypeCompletionAvailable
    self.GetFiletypeCompleter( filetypes )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/server_state.py", line 96, in GetFiletypeCompleter
    raise ValueError(
ValueError: No semantic completer exists for filetypes: ['gitignore']
127.0.0.1 - - [27/Nov/2025 10:29:16] "POST /event_notification HTTP/1.1" 200 2
2025-11-27 10:29:16,818 - INFO - Clangd executable found at /home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin and up to date
2025-11-27 10:29:16,818 - INFO - Using Clangd from /home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd
2025-11-27 10:29:16,818 - INFO - Computed Clangd command: ['/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd', '--header-insertion=never', '-header-insertion-decorators=0', '-resource-dir=/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clang/lib/clang/21.1.3', '-limit-results=500']
2025-11-27 10:29:16,818 - INFO - Completion config: 50, detailing 0 candiates
2025-11-27 10:29:16,818 - INFO - Returning cached Clangd command: ['/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd', '--header-insertion=never', '-header-insertion-decorators=0', '-resource-dir=/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clang/lib/clang/21.1.3', '-limit-results=500']
127.0.0.1 - - [27/Nov/2025 10:29:16] "GET /signature_help_available?subserver=cpp HTTP/1.1" 200 23
127.0.0.1 - - [27/Nov/2025 10:29:16] "POST /event_notification HTTP/1.1" 200 2
2025-11-27 10:29:16,828 - INFO - Adding buffer identifiers for file: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin/Tests/UITest.cpp
2025-11-27 10:29:16,831 - INFO - Starting Clangd: ['/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd', '--header-insertion=never', '-header-insertion-decorators=0', '-resource-dir=/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clang/lib/clang/21.1.3', '-limit-results=500']
2025-11-27 10:29:16,832 - INFO - Clangd started with PID 24448
127.0.0.1 - - [27/Nov/2025 10:29:16] "POST /event_notification HTTP/1.1" 200 2
2025-11-27 10:29:16,840 - INFO - cfamily: Language server does not require resolve request
2025-11-27 10:29:16,840 - INFO - cfamily: Language server requires sync type of Incremental
2025-11-27 10:29:16,840 - INFO - cfamily: Using characters for signature triggers: (,),{,},<,>,,
2025-11-27 10:29:16,841 - ERROR - The language server communication channel closed unexpectedly. Issue a RestartServer command to recover.
Traceback (most recent call last):
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 368, in run
    self._ReadMessages()
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 523, in _ReadMessages
    self._DispatchMessage( lsp.Parse( content ) )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 653, in _DispatchMessage
    self._responses[ message_id ].ResponseReceived( message )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 195, in ResponseReceived
    self._response_callback( self, message )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 2403, in response_handler
    self._HandleInitializeInPollThread( message )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/language_server/language_server_completer.py", line 2544, in _HandleInitializeInPollThread
    handler( self )
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/cpp/clangd_completer.py", line 225, in <lambda>
    lambda self, request_data: self._SendFlagsFromExtraConf( request_data )
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/cpp/clangd_completer.py", line 407, in _SendFlagsFromExtraConf
    flags = BuildCompilationCommand( settings[ 'flags' ], filepath )
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/cpp/clangd_completer.py", line 202, in BuildCompilationCommand
    flags = RemoveUnusedFlags( flags, filepath, enable_windows_style_flags )
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/ycmd/completers/cpp/flags.py", line 410, in RemoveUnusedFlags
    current_flag = flags[ 0 ]
                   ~~~~~^^^^^
IndexError: list index out of range
127.0.0.1 - - [27/Nov/2025 10:29:16] "POST /semantic_completion_available HTTP/1.1" 200 4
2025-11-27 10:29:17,641 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:29:17,641 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:29:17,641 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:29:17,641 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:29:17,641 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:29:17,641 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:29:17,641 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:29:17,641 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:29:17,641 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:29:17,641 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:29:17,641 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:29:17,641 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:29:17,641 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:29:17,641 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:29:17,641 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GetType for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:29:17,642 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:29:17] "POST /defined_subcommands HTTP/1.1" 200 414
2025-11-27 10:29:17,645 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:29:17,645 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:29:17,645 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:29:17,645 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:29:17,645 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:29:17,645 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:29:17,645 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:29:17,645 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:29:17,645 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:29:17,645 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:29:17,646 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:29:17,646 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GetType for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:29:17,646 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:29:17] "POST /run_completer_command HTTP/1.1" 500 1998
127.0.0.1 - - [27/Nov/2025 10:29:19] "POST /debug_info HTTP/1.1" 200 1100
2025-11-27 10:29:26,446 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:29:26,446 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:29:26,446 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:29:26,446 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:29:26,446 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:29:26,446 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:29:26,447 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:29:26,447 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:29:26,447 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:29:26,447 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:29:26,447 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:29:26,447 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GetType for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:29:26,447 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:29:26] "POST /run_completer_command HTTP/1.1" 500 1998
127.0.0.1 - - [27/Nov/2025 10:29:26] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:29:36] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:29:42] "POST /debug_info HTTP/1.1" 200 1100
127.0.0.1 - - [27/Nov/2025 10:29:47] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:29:57] "POST /receive_messages HTTP/1.1" 200 4
2025-11-27 10:30:01,332 - INFO - Adding buffer identifiers for file: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin/Tests/UITest.cpp
127.0.0.1 - - [27/Nov/2025 10:30:01] "POST /event_notification HTTP/1.1" 200 2
2025-11-27 10:30:02,109 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:30:02,109 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:30:02,109 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:30:02,109 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:30:02,109 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:30:02,109 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:30:02,109 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:30:02,109 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:30:02,109 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:30:02,109 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:30:02,109 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:30:02,109 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting GetType for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:30:02,109 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:30:02,110 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:30:02] "POST /run_completer_command HTTP/1.1" 500 1998
127.0.0.1 - - [27/Nov/2025 10:30:08] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:30:18] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:30:28] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:30:38] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:30:49] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:30:59] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:09] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:19] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:23] "POST /debug_info HTTP/1.1" 200 1100
127.0.0.1 - - [27/Nov/2025 10:31:29] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:39] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:49] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:31:59] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:09] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:19] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:29] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:39] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:49] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:32:59] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:33:09] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:33:19] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:33:29] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:33:40] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:33:50] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:00] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:10] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:20] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:30] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:30] "POST /debug_info HTTP/1.1" 200 1100
127.0.0.1 - - [27/Nov/2025 10:34:40] "POST /receive_messages HTTP/1.1" 200 4
2025-11-27 10:34:40,566 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:34:40,567 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:34:40,567 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:34:40,567 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:34:40,567 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:34:40,567 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:34:40,567 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:34:40,567 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:34:40,567 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:34:40,567 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:34:40,567 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:34:40,567 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GetType for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:34:40,567 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:34:40] "POST /run_completer_command HTTP/1.1" 500 1998
127.0.0.1 - - [27/Nov/2025 10:34:50] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:34:58] "POST /debug_info HTTP/1.1" 200 1100
127.0.0.1 - - [27/Nov/2025 10:35:00] "POST /receive_messages HTTP/1.1" 200 4
127.0.0.1 - - [27/Nov/2025 10:35:01] "POST /receive_messages HTTP/1.1" 200 5
2025-11-27 10:35:01,802 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:35:01,802 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:35:01,802 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:35:01,802 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:35:01,802 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:35:01,802 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:35:01,802 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:35:01,802 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:35:01,802 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:35:01,802 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:35:01,802 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:35:01,802 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GetType for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:35:01,803 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:35:01] "POST /run_completer_command HTTP/1.1" 500 1998
2025-11-27 10:35:03,485 - INFO - Found executeCommandProvider support for command ExecuteCommand in cfamily
2025-11-27 10:35:03,485 - INFO - Found codeActionProvider support for command FixIt in cfamily
2025-11-27 10:35:03,485 - INFO - Found definitionProvider support for command GoToDefinition in cfamily
2025-11-27 10:35:03,485 - INFO - Found declarationProvider support for command GoToDeclaration in cfamily
2025-11-27 10:35:03,485 - INFO - Found ('definitionProvider', 'declarationProvider') support for command GoTo in cfamily
2025-11-27 10:35:03,485 - INFO - Found typeDefinitionProvider support for command GoToType in cfamily
2025-11-27 10:35:03,485 - INFO - Found implementationProvider support for command GoToImplementation in cfamily
2025-11-27 10:35:03,485 - INFO - Found referencesProvider support for command GoToReferences in cfamily
2025-11-27 10:35:03,485 - INFO - Found renameProvider support for command RefactorRename in cfamily
2025-11-27 10:35:03,485 - INFO - Found documentFormattingProvider support for command Format in cfamily
2025-11-27 10:35:03,485 - INFO - Found workspaceSymbolProvider support for command GoToSymbol in cfamily
2025-11-27 10:35:03,485 - INFO - Found documentSymbolProvider support for command GoToDocumentOutline in cfamily
2025-11-27 10:35:03,485 - INFO - Always supporting StopServer for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting RestartServer for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GetDoc for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GetType for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting TypeHierarchy for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting ResolveTypeHierarchyItem for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GoToCallees for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GoToCallers for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting CallHierarchy for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting ResolveCallHierarchyItem for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GetTypeImprecise for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GoToImprecise for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GoToInclude for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GetDocImprecise for cfamily
2025-11-27 10:35:03,486 - INFO - Always supporting GoToAlternateFile for cfamily
127.0.0.1 - - [27/Nov/2025 10:35:03] "POST /run_completer_command HTTP/1.1" 500 1998
127.0.0.1 - - [27/Nov/2025 10:35:10] "POST /receive_messages HTTP/1.1" 200 4

Clangd logfile

I[10:29:16.838] clangd version 21.1.3 (https://github.com/ycm-core/llvm 6d06e83ae7dcd53babc43b60d3c6e998b4606314)
I[10:29:16.838] Features: linux
I[10:29:16.838] PID: 24448
I[10:29:16.838] Working directory: /home/svalorzen/Projects/SoundRadix/AddSynth/plugin
I[10:29:16.838] argv[0]: /home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clangd/output/bin/clangd
I[10:29:16.838] argv[1]: --header-insertion=never
I[10:29:16.838] argv[2]: -header-insertion-decorators=0
I[10:29:16.838] argv[3]: -resource-dir=/home/svalorzen/.vim/bundle/YouCompleteMe/third_party/ycmd/third_party/clang/lib/clang/21.1.3
I[10:29:16.838] argv[4]: -limit-results=500
I[10:29:16.838] Starting LSP over stdin/stdout
I[10:29:16.838] <-- initialize(1)
I[10:29:16.839] --> reply:initialize(1) 1 ms
I[10:29:16.841] <-- initialized
I[10:29:16.841] <-- workspace/didChangeConfiguration
E[10:29:16.843] Transport error: Input/output error
I[10:29:16.843] LSP finished, exiting with status 1

Output of YcmDiags

No warnings or errors detected.

Output of git rev-parse HEAD in YouCompleteMe installation directory

d11e24d618f672333d788ec6c582c8f25b0b0092

[puremourning]

You're not going to get very far with an empty flags list for every file, so while I admit it's annoying that we have a bug here, I'm not going to spend time to fix it. If you want to raise a PR for it with a regression test, then we'd probably merge it.