1.24.3+: clang-format 20.1.0 fails for .c files if a .clang-format file uses "Language: Cpp" instead of "Language: C"

[MaJerle]

Environment

Version: 1.98.2 (user setup)
Commit: ddc367ed5c8936efe395cffeec279b04ffd7db78
Date: 2025-03-12T13:32:45.399Z
Electron: 34.2.0
ElectronBuildId: 11161602
Chromium: 132.0.6834.196
Node.js: 20.18.2
V8: 13.2.152.36-electron.0
OS: Windows_NT x64 10.0.26100

C/C++

Name: C/C++
Id: ms-vscode.cpptools
Description: C/C++ IntelliSense, debugging, and code browsing.
Version: 1.24.3
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools

Bug Summary and Steps to Reproduce

With the latest vscode & C/C++ update, I noticed that formatting does not work anymore. I use the formatOnSave with file parameter. The .clang-format exists and it is properly detected.

In the Output/C/C++ window I get this:

Formatting failed:
c:\my\path\.vscode\extensions\ms-vscode.cpptools-1.24.3-win32-x64/bin/../LLVM/bin/clang-format.exe --style=file --fallback-style=LLVM --Wno-error=unknown --assume-filename=D:\my\path\main.c D:\MY\PATH\MAIN.C
Configuration file(s) do(es) not support C: D:\my\path\.clang-format, D:\myroot\.clang-format

Clang format I use for very long time

---
Language: Cpp
# BasedOnStyle:  LLVM
AccessModifierOffset: -2
AlignAfterOpenBracket: Align
AlignArrayOfStructures: None
AlignConsecutiveMacros:
  Enabled: true
  AcrossEmptyLines: true
  AcrossComments: true
AlignConsecutiveAssignments: None
AlignConsecutiveBitFields:
  Enabled: true
  AcrossEmptyLines: true
  AcrossComments: true
AlignConsecutiveDeclarations: None
AlignEscapedNewlines: Right
AlignOperands: Align
SortIncludes: true
InsertBraces: true # Control statements must have curly brackets
AlignTrailingComments: true
AllowAllArgumentsOnNextLine: true
AllowAllParametersOfDeclarationOnNextLine: true
AllowShortEnumsOnASingleLine: true
AllowShortBlocksOnASingleLine: Empty
AllowShortCaseLabelsOnASingleLine: true
AllowShortFunctionsOnASingleLine: All
AllowShortLambdasOnASingleLine: All
AllowShortIfStatementsOnASingleLine: Never
AllowShortLoopsOnASingleLine: false
AlwaysBreakAfterDefinitionReturnType: None
AlwaysBreakAfterReturnType: AllDefinitions
AlwaysBreakBeforeMultilineStrings: false
AlwaysBreakTemplateDeclarations: Yes
AttributeMacros:
  - __capability
BinPackArguments: true
BinPackParameters: true
BraceWrapping:
  AfterCaseLabel: false
  AfterClass: false
  AfterControlStatement: Never
  AfterEnum: false
  AfterFunction: false
  AfterNamespace: false
  AfterObjCDeclaration: false
  AfterStruct: false
  AfterUnion: false
  AfterExternBlock: false
  BeforeCatch: false
  BeforeElse: false
  BeforeLambdaBody: false
  BeforeWhile: false
  IndentBraces: false
  SplitEmptyFunction: true
  SplitEmptyRecord: true
  SplitEmptyNamespace: true
BreakBeforeBinaryOperators: NonAssignment
BreakBeforeConceptDeclarations: true
BreakBeforeBraces: Attach
BreakBeforeInheritanceComma: false
BreakInheritanceList: BeforeColon
BreakBeforeTernaryOperators: true
BreakConstructorInitializersBeforeComma: false
BreakConstructorInitializers: BeforeColon
BreakAfterJavaFieldAnnotations: false
BreakStringLiterals: true
ColumnLimit: 120
CommentPragmas: "^ IWYU pragma:"
QualifierAlignment: Leave
CompactNamespaces: false
ConstructorInitializerIndentWidth: 4
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DeriveLineEnding: true
DerivePointerAlignment: false
DisableFormat: false
EmptyLineAfterAccessModifier: Never
EmptyLineBeforeAccessModifier: LogicalBlock
ExperimentalAutoDetectBinPacking: false
PackConstructorInitializers: BinPack
BasedOnStyle: ""
ConstructorInitializerAllOnOneLineOrOnePerLine: false
AllowAllConstructorInitializersOnNextLine: true
FixNamespaceComments: true
ForEachMacros:
  - foreach
  - Q_FOREACH
  - BOOST_FOREACH
IfMacros:
  - KJ_IF_MAYBE
IncludeBlocks: Preserve
IncludeCategories:
  - Regex: "^<(.*)>"
    Priority: 0
  - Regex: '^"(.*)"'
    Priority: 1
  - Regex: "(.*)"
    Priority: 2
IncludeIsMainRegex: "(Test)?$"
IncludeIsMainSourceRegex: ""
IndentAccessModifiers: false
IndentCaseLabels: true
IndentCaseBlocks: false
IndentGotoLabels: true
IndentPPDirectives: None
IndentExternBlock: AfterExternBlock
IndentRequires: true
IndentWidth: 4
IndentWrappedFunctionNames: false
InsertTrailingCommas: None
JavaScriptQuotes: Leave
JavaScriptWrapImports: true
KeepEmptyLinesAtTheStartOfBlocks: true
LambdaBodyIndentation: Signature
MacroBlockBegin: ""
MacroBlockEnd: ""
MaxEmptyLinesToKeep: 1
NamespaceIndentation: None
ObjCBinPackProtocolList: Auto
ObjCBlockIndentWidth: 2
ObjCBreakBeforeNestedBlockParam: true
ObjCSpaceAfterProperty: false
ObjCSpaceBeforeProtocolList: true
PenaltyBreakAssignment: 2
PenaltyBreakBeforeFirstCallParameter: 19
PenaltyBreakComment: 300
PenaltyBreakFirstLessLess: 120
PenaltyBreakOpenParenthesis: 0
PenaltyBreakString: 1000
PenaltyBreakTemplateDeclaration: 10
PenaltyExcessCharacter: 1000000
PenaltyReturnTypeOnItsOwnLine: 60
PenaltyIndentedWhitespace: 0
PointerAlignment: Left
PPIndentWidth: -1
ReferenceAlignment: Pointer
ReflowComments: false
RemoveBracesLLVM: false
SeparateDefinitionBlocks: Always
ShortNamespaceLines: 1
SortJavaStaticImport: Before
SortUsingDeclarations: true
SpaceAfterCStyleCast: false
SpaceAfterLogicalNot: false
SpaceAfterTemplateKeyword: true
SpaceBeforeAssignmentOperators: true
SpaceBeforeCaseColon: false
SpaceBeforeParens: ControlStatements
SpaceBeforeParensOptions:
  AfterControlStatements: true
  AfterForeachMacros: true
  AfterFunctionDefinitionName: false
  AfterFunctionDeclarationName: false
  AfterIfMacros: true
  AfterOverloadedOperator: false
  BeforeNonEmptyParentheses: false
SpaceAroundPointerQualifiers: Default
SpaceBeforeRangeBasedForLoopColon: true
SpaceInEmptyBlock: false
SpaceInEmptyParentheses: false
SpacesBeforeTrailingComments: 1
SpacesInAngles: Never
SpacesInConditionalStatement: false
SpacesInContainerLiterals: true
SpacesInCStyleCastParentheses: false
SpacesInLineCommentPrefix:
  Minimum: 1
  Maximum: -1
SpacesInParentheses: false
SpacesInSquareBrackets: false
SpaceBeforeSquareBrackets: false
BitFieldColonSpacing: Both
Standard: Latest
StatementAttributeLikeMacros:
  - Q_EMIT
StatementMacros:
  - Q_UNUSED
  - QT_REQUIRE_VERSION
TabWidth: 8
UseCRLF: false
UseTab: Never
WhitespaceSensitiveMacros:
  - STRINGIZE
  - PP_STRINGIZE
  - BOOST_PP_STRINGIZE
  - NS_SWIFT_NAME
  - CF_SWIFT_NAME
SpaceBeforeCpp11BracedList: false
SpaceBeforeCtorInitializerColon: true
SpaceBeforeInheritanceColon: true
---

Configuration and Logs

-------- Diagnostics - 3/23/2025, 8:38:40 AM
Version: 1.24.3
Current Configuration:
{
    "name": "Win32",
    "intelliSenseMode": "windows-gcc-x64",
    "configurationProvider": "ms-vscode.cmake-tools",
    "compilerPathIsExplicit": false,
    "cStandardIsExplicit": false,
    "cppStandardIsExplicit": false,
    "intelliSenseModeIsExplicit": false,
    "configurationProviderInCppPropertiesJson": "ms-vscode.cmake-tools",
    "includePath": [],
    "cStandard": "c17",
    "cppStandard": "gnu++17",
    "mergeConfigurations": false,
    "compilerPath": "C:\\msys64\\mingw64\\bin\\gcc.exe",
    "browse": {
        "limitSymbolsToIncludedHeaders": true
    }
}
Modified Settings:
{
    "C_Cpp.codeAnalysis.clangTidy.codeAction.formatFixes": false,
    "C_Cpp.codeAnalysis.clangTidy.enabled": true,
    "C_Cpp.codeAnalysis.clangTidy.useBuildPath": true,
    "C_Cpp.addNodeAddonIncludePaths": true
}
Additional Tracked Settings:
{
    "editorTabSize": 4,
    "editorInsertSpaces": true,
    "editorAutoClosingBrackets": "languageDefined",
    "filesEncoding": "utf8",
    "filesAssociations": {
        "*.lcdjson": "json",
        "string.h": "c",
        "compare": "c",
        "bitset": "c",
        "stdio.h": "c",
        "test.h": "c"
    },
    "filesExclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": true,
        "**/.DS_Store": true,
        "**/Thumbs.db": true
    },
    "filesAutoSaveAfterDelay": false,
    "editorInlayHintsEnabled": true,
    "editorParameterHintsEnabled": true,
    "searchExclude": {
        "**/node_modules": true,
        "**/bower_components": true,
        "**/*.code-search": true
    },
    "workbenchSettingsEditor": "ui"
}
Custom browse configuration: 
{
    "browsePath": [
        "d:/my/path/dev",
        "d:/my/path/tests",
    ],
    "compilerPath": "c:/msys64/mingw32/bin/i686-w64-mingw32-gcc.exe",
    "compilerArgs": [],
    "compilerFragments": [
        "-g",
        "-Wall",
        "-Wextra",
        "-Wpedantic"
    ]
}
cpptools version (native): 1.24.3.0
Current database path: C:\MY\PATH\APPDATA\LOCAL\MICROSOFT\VSCODE-CPPTOOLS\8717E89F3C1315DC5262EF171675A49B\.BROWSE.VC.DB
Translation Unit Mappings:
[ D:\my\path\src\file.c - source TU]:
Translation Unit Configurations:
[ D:\my\path\src\file.c ]
    Process ID: 24128
    Memory Usage: 54 MB
    Compiler Path: C:\msys64\mingw32\bin\i686-w64-mingw32-gcc.exe
    Include paths:
        include: D:\my\path\src\include
        system include: C:\msys64\mingw32\lib\gcc\i686-w64-mingw32\14.1.0\include
        system include: C:\msys64\mingw32\include
        system include: C:\msys64\mingw32\lib\gcc\i686-w64-mingw32\14.1.0\include-fixed
    Defines:
        CONSOLE
        WIN32
        _DEBUG
    Standard Version: c17
    IntelliSense Mode: windows-gcc-x86
    Other Flags:
        --gcc
        --gnu_version=140100
Total Memory Usage: 54 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 10103

Other Extensions

No response

Additional context

No response

[sean-mcmanus]

@MaJerle It's a regression with 1.24.3. You can downgrade to 1.24.2 as a workaround until we release a fix in 1.24.4.

[sean-mcmanus]

@MaJerle Actually, this appears to be caused by your .clang-format having a Cpp language and clang-format 20.1.0 has changed the behavior such that it fails when run on a .c file that it interprets as C and not C++, i.e. it works when setting the C_Cpp.clang_format_path to a 19.1.7 clang-format.

Can you change your .clang-format file to use Language: C instead or add an additional section for C?

[sean-mcmanus]

We could potentially detect if the .c file is actually associated with C++ and change the --assume-filename extension path to match the file association.

[MaJerle]

It works if I move to C from Cpp but I am now forced to do the 2 identical configs.

What is the point of assume filename parameter? What are we solving with this?

[bobbrow]

I am now forced to do the 2 configs.

What is the point of assume filename parameter? What are we solving with this?

assume filename is required because we support formatting of unsaved changes to your files. This means that the C++ extension sends the current file contents to clang-format instead of having clang-format read the outdated version from disk.

[MaJerle]

Can this be an optional parameter in the settings instead? It breaks many things from the past, and I assume I am not the only one here.

[bobbrow]

I'm pretty sure if we pass main.c to clang-format and have it read from disk you'll have the exact same problem with clang-format assuming it's a C file. For now, I think we'll downgrade back to clang-format 19.1.7 and try to convince the LLVM folks to keep the old behavior.