[19.1.0] clangd crashes while running boost-use-ranges clang-tidy check

[xb284524239]

My Environment：

OS: Windows 10
LLVM Version: 19.1.0 (include clangd、clang-tidy、clang++, etc.)
CMake Version: 3.30.3 
IDE: VSCode

Problem Description: I have found after multiple attempts that when I configure the .clang-tidy file in the root directory of my project, the Clang Language Server frequently crashes to the point of being completely unusable. However, when I delete the .clang-tidy file, everything returns to normal.

The .clang-tidy file:

Checks: "
        *,
        -llvmlibc-*,
        -fuchsia-*,
"

[EugeneZelenko]

@xb284524239: Could you please try to run Clang-tidy standalone? Just to narrow down source of problem.

[xb284524239]

@xb284524239: Could you please try to run Clang-tidy standalone? Just to narrow down source of problem.

PS C:\Users\paul> clang-tidy --version
LLVM (http://llvm.org/):
  LLVM version 19.1.0
  Optimized build.
PS C:\Users\paul>

@EugeneZelenko Hello, I usually use it via VSCode. Could you please tell me how to use Clang-tidy standalone?

[EugeneZelenko]

See https://clang.llvm.org/extra/clang-tidy/. There is also run-clang-tidy script to run on compile database (could be generated by CMake).

[EugeneZelenko]

run-clang-tidy deals with compile database.

[xb284524239]

I would like to add that a few days ago, when I was using version 18.1.8 of LLVM, the Clang Language Server did not crash. The frequent crashes only started after I upgraded LLVM to version 19.1.0. Perhaps this information could be helpful in troubleshooting the problem.

run-clang-tidy:

PS C:\Workspace\VSCode_Workspace\Test004> python "C:\Program Files\LLVM\bin\run-clang-tidy" -p "./build"
Enabled checks:
    abseil-cleanup-ctad
    abseil-duration-addition
    abseil-duration-comparison
    abseil-duration-conversion-cast
    abseil-duration-division
    abseil-duration-factory-float
    abseil-duration-factory-scale
    abseil-duration-subtraction
    abseil-duration-unnecessary-conversion
    abseil-faster-strsplit-delimiter
    abseil-no-internal-dependencies
    abseil-no-namespace
    abseil-redundant-strcat-calls
    abseil-str-cat-append
    abseil-string-find-startswith
    abseil-string-find-str-contains
    abseil-time-comparison
    abseil-time-subtraction
    abseil-upgrade-duration-conversions
    altera-id-dependent-backward-branch
    altera-kernel-name-restriction
    altera-single-work-item-barrier
    altera-struct-pack-align
    altera-unroll-loops
    android-cloexec-accept
    android-cloexec-accept4
    android-cloexec-creat
    android-cloexec-dup
    android-cloexec-epoll-create
    android-cloexec-epoll-create1
    android-cloexec-fopen
    android-cloexec-inotify-init
    android-cloexec-inotify-init1
    android-cloexec-memfd-create
    android-cloexec-open
    android-cloexec-pipe
    android-cloexec-pipe2
    android-cloexec-socket
    android-comparison-in-temp-failure-retry
    boost-use-ranges
    boost-use-to-string
    bugprone-argument-comment
    bugprone-assert-side-effect
    bugprone-assignment-in-if-condition
    bugprone-bad-signal-to-kill-thread
    bugprone-bool-pointer-implicit-conversion
    bugprone-branch-clone
    bugprone-casting-through-void
    bugprone-chained-comparison
    bugprone-compare-pointer-to-member-virtual-function
    bugprone-copy-constructor-init
    bugprone-crtp-constructor-accessibility
    bugprone-dangling-handle
    bugprone-dynamic-static-initializers
    bugprone-easily-swappable-parameters
    bugprone-empty-catch
    bugprone-exception-escape
    bugprone-fold-init-type
    bugprone-forward-declaration-namespace
    bugprone-forwarding-reference-overload
    bugprone-implicit-widening-of-multiplication-result
    bugprone-inaccurate-erase
    bugprone-inc-dec-in-conditions
    bugprone-incorrect-enable-if
    bugprone-incorrect-roundings
    bugprone-infinite-loop
    bugprone-integer-division
    bugprone-lambda-function-name
    bugprone-macro-parentheses
    bugprone-macro-repeated-side-effects
    bugprone-misplaced-operator-in-strlen-in-alloc
    bugprone-misplaced-pointer-arithmetic-in-alloc
    bugprone-misplaced-widening-cast
    bugprone-move-forwarding-reference
    bugprone-multi-level-implicit-pointer-conversion
    bugprone-multiple-new-in-one-expression
    bugprone-multiple-statement-macro
    bugprone-narrowing-conversions
    bugprone-no-escape
    bugprone-non-zero-enum-to-bool-conversion
    bugprone-not-null-terminated-result
    bugprone-optional-value-conversion
    bugprone-parent-virtual-call
    bugprone-pointer-arithmetic-on-polymorphic-object
    bugprone-posix-return
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    bugprone-shared-ptr-array-mismatch
    bugprone-signal-handler
    bugprone-signed-char-misuse
    bugprone-sizeof-container
    bugprone-sizeof-expression
    bugprone-spuriously-wake-up-functions
    bugprone-standalone-empty
    bugprone-string-constructor
    bugprone-string-integer-assignment
    bugprone-string-literal-with-embedded-nul
    bugprone-stringview-nullptr
    bugprone-suspicious-enum-usage
    bugprone-suspicious-include
    bugprone-suspicious-memory-comparison
    bugprone-suspicious-memset-usage
    bugprone-suspicious-missing-comma
    bugprone-suspicious-realloc-usage
    bugprone-suspicious-semicolon
    bugprone-suspicious-string-compare
    bugprone-suspicious-stringview-data-usage
    bugprone-swapped-arguments
    bugprone-switch-missing-default-case
    bugprone-terminating-continue
    bugprone-throw-keyword-missing
    bugprone-too-small-loop-variable
    bugprone-unchecked-optional-access
    bugprone-undefined-memory-manipulation
    bugprone-undelegated-constructor
    bugprone-unhandled-exception-at-new
    bugprone-unhandled-self-assignment
    bugprone-unique-ptr-array-mismatch
    bugprone-unsafe-functions
    bugprone-unused-local-non-trivial-variable
    bugprone-unused-raii
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    bugprone-use-after-move
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    clang-analyzer-optin.mpi.MPI-Checker
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    clang-analyzer-optin.performance.GCDAntipattern
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    clang-analyzer-optin.portability.UnixAPI
    clang-analyzer-optin.taint.TaintedAlloc
    clang-analyzer-osx.API
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    clang-analyzer-osx.NSOrCFErrorDerefChecker
    clang-analyzer-osx.NumberObjectConversion
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    clang-analyzer-osx.ObjCProperty
    clang-analyzer-osx.SecKeychainAPI
    clang-analyzer-osx.cocoa.AtSync
    clang-analyzer-osx.cocoa.AutoreleaseWrite
    clang-analyzer-osx.cocoa.ClassRelease
    clang-analyzer-osx.cocoa.Dealloc
    clang-analyzer-osx.cocoa.IncompatibleMethodTypes
    clang-analyzer-osx.cocoa.Loops
    clang-analyzer-osx.cocoa.MissingSuperCall
    clang-analyzer-osx.cocoa.NSAutoreleasePool
    clang-analyzer-osx.cocoa.NSError
    clang-analyzer-osx.cocoa.NilArg
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    clang-analyzer-osx.cocoa.SelfInit
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    clang-analyzer-osx.coreFoundation.CFError
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    clang-analyzer-osx.coreFoundation.containers.OutOfBounds
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    clang-analyzer-security.FloatLoopCounter
    clang-analyzer-security.PutenvStackArray
    clang-analyzer-security.SetgidSetuidOrder
    clang-analyzer-security.cert.env.InvalidPtr
    clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling
    clang-analyzer-security.insecureAPI.SecuritySyntaxChecker
    clang-analyzer-security.insecureAPI.UncheckedReturn
    clang-analyzer-security.insecureAPI.bcmp
    clang-analyzer-security.insecureAPI.bcopy
    clang-analyzer-security.insecureAPI.bzero
    clang-analyzer-security.insecureAPI.decodeValueOfObjCType
    clang-analyzer-security.insecureAPI.getpw
    clang-analyzer-security.insecureAPI.gets
    clang-analyzer-security.insecureAPI.mkstemp
    clang-analyzer-security.insecureAPI.mktemp
    clang-analyzer-security.insecureAPI.rand
    clang-analyzer-security.insecureAPI.strcpy
    clang-analyzer-security.insecureAPI.vfork
    clang-analyzer-unix.API
    clang-analyzer-unix.BlockInCriticalSection
    clang-analyzer-unix.DynamicMemoryModeling
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    clang-analyzer-unix.StdCLibraryFunctions
    clang-analyzer-unix.Stream
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    clang-analyzer-unix.cstring.BadSizeArg
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    clang-analyzer-webkit.NoUncountedMemberChecker
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    clang-analyzer-webkit.UncountedLambdaCapturesChecker
    concurrency-mt-unsafe
    concurrency-thread-canceltype-asynchronous
    cppcoreguidelines-avoid-c-arrays
    cppcoreguidelines-avoid-capturing-lambda-coroutines
    cppcoreguidelines-avoid-const-or-ref-data-members
    cppcoreguidelines-avoid-do-while
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    cppcoreguidelines-avoid-reference-coroutine-parameters
    cppcoreguidelines-c-copy-assignment-signature
    cppcoreguidelines-explicit-virtual-functions
    cppcoreguidelines-init-variables
    cppcoreguidelines-interfaces-global-init
    cppcoreguidelines-macro-to-enum
    cppcoreguidelines-macro-usage
    cppcoreguidelines-misleading-capture-default-by-value
    cppcoreguidelines-missing-std-forward
    cppcoreguidelines-narrowing-conversions
    cppcoreguidelines-no-malloc
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    cppcoreguidelines-noexcept-destructor
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    cppcoreguidelines-owning-memory
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    cppcoreguidelines-pro-bounds-array-to-pointer-decay
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    cppcoreguidelines-pro-type-const-cast
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    cppcoreguidelines-pro-type-reinterpret-cast
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    cppcoreguidelines-rvalue-reference-param-not-moved
    cppcoreguidelines-slicing
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    google-readability-avoid-underscore-in-googletest-name
    google-readability-braces-around-statements
    google-readability-casting
    google-readability-function-size
    google-readability-namespace-comments
    google-readability-todo
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    google-runtime-operator
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    modernize-macro-to-enum
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    readability-suspicious-call-argument
    readability-uniqueptr-delete-release
    readability-uppercase-literal-suffix
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Running clang-tidy for 2 files out of 2 in compilation database ...
[1/2][0.1s] C:\Program Files\LLVM\bin\clang-tidy.EXE -p=./build C:\Workspace\VSCode_Workspace\Test004\main.cpp
C:\Workspace\VSCode_Workspace\Test004\main.cpp:23:5: warning: use a trailing return type for this function [modernize-use-trailing-return-type]
   23 | int main(int argc, char** argv) {
      | ~~~ ^
      | auto                            -> int
C:\Workspace\VSCode_Workspace\Test004\main.cpp:23:14: warning: parameter 'argc' is unused [misc-unused-parameters]
   23 | int main(int argc, char** argv) {
      |              ^~~~
      |               /*argc*/
C:\Workspace\VSCode_Workspace\Test004\main.cpp:23:27: warning: parameter 'argv' is unused [misc-unused-parameters]
   23 | int main(int argc, char** argv) {
      |                           ^~~~
      |                            /*argv*/
4 warnings generated.
Suppressed 1 warnings (1 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

[2/2][18.4s] C:\Program Files\LLVM\bin\clang-tidy.EXE -p=./build C:\Workspace\VSCode_Workspace\Test004\test.cpp
93662 warnings generated.
Suppressed 93662 warnings (93662 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

PS C:\Workspace\VSCode_Workspace\Test004>

[xb284524239]

@EugeneZelenko Hello Sir,

After multiple tests, I have finally identified the cause of the Clang Language Server crashes. The specific reasons are as follows:

1. The following .clang-tidy configuration file causes the Clang Language Server to crash:

Checks: "
        *
"

2. The following .clang-tidy configuration file does not cause the Clang Language Server to crash:

   Checks: "
       *,
       -boost-use-ranges
   "

The only difference between the two configuration files is that the second one includes an additional -boost-use-ranges configuration. Therefore, I suspect that there is a bug in clang-tidy.exe when handling the boost-use-ranges check, which leads to the Clang Language Server crashing.

By the way, my project is a very simple Hello-World-level demo and does not use the Boost library. If needed, I can send you my demo code (for testing purposes).

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Paul Xu (xb284524239)

``` My Environment： OS: Windows 10 LLVM Version: 19.1.0 (include clangd、clang-tidy、clang++, etc.) CMake Version: 3.30.3 IDE: VSCode ``` Problem Description: I have found after multiple attempts that when I configure the `.clang-tidy` file in the root directory of my project, the Clang Language Server frequently crashes to the point of being completely unusable. However, when I delete the `.clang-tidy` file, everything returns to normal. The `.clang-tidy` file: ``` Checks: " *, -llvmlibc-*, -fuchsia-*, " ```  

[EugeneZelenko]

@xb284524239: Please provide reproducer. https://godbolt.org should be helpful.

[xb284524239]

@EugeneZelenko

Hello, here is my demo code, and I have recorded a video to reproduce the issue. In my video, there is only one check item in the .clang-tidy file: boost-use-ranges. If I delete this check item or modify it to -boost-use-ranges, then the Clang Language Server will not crash.

# CMakeLists.txt

cmake_minimum_required(VERSION 3.30)
project(Test006 VERSION 0.1.0 LANGUAGES C CXX)
add_executable(Test006 main.cpp test.cpp)

// main.cpp

#include "test.h"
int main(int, char **) { test(); }

// test.h

#pragma once
void test();

// test.cpp

#include "test.h"
#include <iostream>
void test() {
  std::cout << "Hello, I'm only use for testing clang-tidy!" << std::endl;
}

// .clang-tidy

Checks: "boost-use-ranges"

https://github.com/user-attachments/assets/8d2afcb4-fab5-468c-b126-b18d36fbf154

[HighCommander4]

Thank you @xb284524239 for the reduced code example. I can reproduce the crash using this example.

The crash occurs when opening test.cpp, but interestingly, it seems to only happen if test.h has been opened previously.

I have not been able to reproduce the crash with clangd --check=test.cpp, or with clang-tidy on the command line, which suggests that even though the crash is in a clang-tidy checker, it may only occur when the checker is run via clangd.

[llvmbot]

@llvm/issue-subscribers-clangd

Author: Paul Xu (xb284524239)

``` My Environment： OS: Windows 10 LLVM Version: 19.1.0 (include clangd、clang-tidy、clang++, etc.) CMake Version: 3.30.3 IDE: VSCode ``` Problem Description: I have found after multiple attempts that when I configure the `.clang-tidy` file in the root directory of my project, the Clang Language Server frequently crashes to the point of being completely unusable. However, when I delete the `.clang-tidy` file, everything returns to normal. The `.clang-tidy` file: ``` Checks: " *, -llvmlibc-*, -fuchsia-*, " ```  

[HighCommander4]

The reason for the crash is that UseRangesCheck::getReplacerMap() is capturing the local variable Results in the static lambda AddFrom. Since the lambda is static, when the function is called a second time, the lambda still references and uses the Result variable from the first invocation, which has been destroyed by that point. (Credit to @hia3 for spotting this here.)

To trigger the crash, it's sufficient to just open any two files in clangd with this checker enabled, even if the contents are empty, since each time a file is opened clangd will call into this function when registering the matchers for the checker.

The function does get called once for each source file with clang-tidy as well (e.g. with clang-tidy source1.cpp source2.cpp it will get called twice), but since the calls occur in sequence on the same thread, in my local testing the crash is avoided because the local variable has the same address each time. (It's still undefined behaviour, of course.) Clangd on the other hand will handle each file on its own thread, and thus with local variables stored in a different region on the stack, and the crash occurs fairly readily.

[HighCommander4]

Proposed fix: https://github.com/llvm/llvm-project/pull/111282

[xb284524239]

The reason for the crash is that UseRangesCheck::getReplacerMap() is capturing the local variable Results in the static lambda AddFrom. Since the lambda is static, when the function is called a second time, the lambda still references and uses the Result variable from the first invocation, which has been destroyed by that point. (Credit to @hia3 for spotting this here.)

To trigger the crash, it's sufficient to just open any two files in clangd with this checker enabled, even if the contents are empty, since each time a file is opened clangd will call into this function when registering the matchers for the checker.

The function does get called once for each source file with clang-tidy as well (e.g. with clang-tidy source1.cpp source2.cpp it will get called twice), but since the calls occur in sequence on the same thread, in my local testing the crash is avoided because the local variable has the same address each time. (It's still undefined behaviour, of course.) Clangd on the other hand will handle each file on its own thread, and thus with local variables stored in a different region on the stack, and the crash occurs fairly readily.

@HighCommander4 Thank you for telling me the reason.