# How to prevent clang-tidy to check sources added with FetchContents?
**URL:** https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871
**Category:** Code
**Created:** [March 2, 2021, 6:26pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871 "2021-03-02T18:26:09Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [March 2, 2021, 6:26pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/1 "2021-03-02T18:26:09Z")
The example use `cxxopts` which was fetched with `CPM.cmake` using `FetchContents`:
```auto
builddriver executing: 'run-clang-tidy.py -p build/standalone -checks=-*,modernize-*,misc-*,hicpp-*,cert-*,readability-*,portability-*,performance-*,google-* standalone'
Compilation SUCCEED in 8.628576 seconds
Number of warnings: 238
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='51', severity='warning', message="declaration uses identifier 'CXXOPTS__VERSION_MAJOR', which is a reserved identifier [cert-dcl37-c,cert-dcl51-cpp]", column='9')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='52', severity='warning', message="declaration uses identifier 'CXXOPTS__VERSION_MINOR', which is a reserved identifier [cert-dcl37-c,cert-dcl51-cpp]", column='9')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='53', severity='warning', message="declaration uses identifier 'CXXOPTS__VERSION_PATCH', which is a reserved identifier [cert-dcl37-c,cert-dcl51-cpp]", column='9')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='212', severity='warning', message="use 'using' instead of 'typedef' [modernize-use-using]", column='3')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='216', severity='warning', message='use a trailing return type for this function [modernize-use-trailing-return-type]', column='3')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='223', severity='warning', message='use a trailing return type for this function [modernize-use-trailing-return-type]', column='3')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='230', severity='warning', message='use a trailing return type for this function [modernize-use-trailing-return-type]', column='3')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='230', severity='warning', message="non-const reference parameter 's', make it const or use a pointer [google-runtime-references]", column='23')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='230', severity='warning', message="the parameter 'a' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param]", column='33')
WarningErrorEntry(path='/Users/clausklein/.cache/CPM/cxxopts/d5c328043c71a6a5670c290d8646b093756db962/include/cxxopts.hpp', lineno='232', severity='warning', message='passing result of std::move() as a const reference argument; no move will actually happen [hicpp-move-const-arg,performance-move-const-arg]', column='21')
# . . .
```
### Hint: all headers included with `#include<...> ` and found with `-isystem` are suppressed by default (at least by `gcc` and `clang` compilers)
When the library is installed and used with `find_package(cxxopts)` it works fine.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [March 2, 2021, 6:26pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/2 "2021-03-02T18:26:57Z")
### This fix it temporarily:
```bash
perl -i.bak -pe 's#-I($CPM_SOURCE_CACHE)#-isystem $1#g' build/install/compile_commands.json
run-clang-tidy.py -p build/install source
# . . .
# no warnings
```
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [March 2, 2021, 6:44pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/3 "2021-03-02T18:44:28Z")
You can wrap your `FetchContent` call with:
```cmake
foreach (lang IN ITEMS C CXX)
set("CMAKE_${lang}_CLANG_TIDY_save" "${CMAKE_${lang}_CLANG_TIDY}")
set("CMAKE_${lang}_CLANG_TIDY" "")
endforeach ()
FetchContent()
foreach (lang IN ITEMS C CXX)
set("CMAKE_${lang}_CLANG_TIDY" "${CMAKE_${lang}_CLANG_TIDY_save}")
endforeach ()
```
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [March 3, 2021, 9:27am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/4 "2021-03-03T09:27:06Z")
> [@ben.boeckel](#):
>
> ```auto
> foreach (lang IN ITEMS C CXX)
> set("CMAKE_${lang}_CLANG_TIDY_save" "${CMAKE_${lang}_CLANG_TIDY}")
> set("CMAKE_${lang}_CLANG_TIDY" "")
> endforeach ()
> FetchContent_MakeAvailable(...)
> foreach (lang IN ITEMS C CXX)
> set("CMAKE_${lang}_CLANG_TIDY" "${CMAKE_${lang}_CLANG_TIDY_save}")
> endforeach ()
>
> ```
unfortunately it doesn’t help ☹
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [March 3, 2021, 9:43am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/5 "2021-03-03T09:43:19Z")
## in general, there are 2 problems to solve
### 1.) the generated build files i.e. `rules.nina`
```auto
rule CXX_COMPILER__fmt_Debug
depfile = $DEP_FILE
deps = gcc
command = /usr/local/Cellar/cmake/3.19.5/bin/cmake -E __run_co_compile --launcher=ccache --tidy="clang-tidy;--extra-arg-before=--driver-mode=g++" --source=$in -- /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ $DEFINES $INCLUDES $FLAGS -MMD -o $out -c $in
description = Building CXX object $out
```
### 2.) the compile\_commands.json file
see [How to prevent clang-tidy to check sources added with FetchContents? - #2 by ClausKlein](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/2)
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [March 3, 2021, 12:20pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/6 "2021-03-03T12:20:01Z")
@craig.scott do you have any idea about it?
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [March 3, 2021, 12:32pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/7 "2021-03-03T12:32:05Z")
I would have expected @ben.boeckel’s suggestion to work. I’m not able to dig deeper into this right now, sorry.
---
### Author:  [@Leon0402](https://discourse.cmake.org/u/Leon0402)
#### Post date: [September 1, 2021, 7:52am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/8 "2021-09-01T07:52:45Z")
Is this the same as [Disable warning on fetched projects](https://discourse.cmake.org/t/disable-warning-on-fetched-projects/1978)?
See the solution from the first post. This is what I do for every library. It works great. So if you compile your project ABC it will use isystem for your lib XYZ (gcc / clang).
I’m not quite sure about compiler warnings though. In the first run it will also compile XYZ and therefore might show some compiler warnings. I haven’t yet investigated this.
But it’s only the first time anyway, so no harm really. And it seems to be compiler warnings and not clang tidy
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 7, 2022, 9:57am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/9 "2022-10-07T09:57:44Z")
CMake 3.25 is adding a new `SYSTEM` target property. It is initialised from a corresponding `SYSTEM` directory property, and both `add_subdirectory()` and `FetchContent_Declare()` are gaining an associated `SYSTEM` keyword as well. I’m starting to wonder if we may want to disable all linters, checkers and verification tasks on targets that have their `SYSTEM` property set to true.
Maybe we could have a dedicated target property for whether checkers should be enabled in case someone wants to enable checking on a target marked `SYSTEM`. We could fall back to the `SYSTEM` property if that dedicated property isn’t set.
I haven’t thought this through, nor have an appreciation for how easy or hard it would be to implement, but it seemed worth mentioning for further discussion.
---
### Author:  [@benthevining](https://discourse.cmake.org/u/benthevining)
#### Post date: [November 7, 2022, 7:23pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/10 "2022-11-07T19:23:31Z")
+1 for this idea!!
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [November 8, 2022, 6:05am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/11 "2022-11-08T06:05:08Z")
- With this `SYSTEM` property, compiler warnings are prevented.
- For `static code analyser`, this may may be used as a workaround: [GitHub - aminya/project\_options: A general-purpose CMake library that provides functions that improve the CMake experience following the best practices.](https://github.com/aminya/project_options#disabling-static-analysis-for-external-targets)
---
### Author:  [@tvercaut](https://discourse.cmake.org/u/tvercaut)
#### Post date: [April 19, 2023, 9:22am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/12 "2023-04-19T09:22:43Z")
Apologies for reviving this thread. I thought adding the `SYSTEM` property to `FetchContent_Declare` for googletest would be silencing the clang-tidy messages arising from googletest but this was not the case. It took me a bit of time to sort it out. I hope this can help others. My workaround is now to set `CXX_CLANG_TIDY` (not `CMAKE_CXX_CLANG_TIDY`) to be empty for the `gtest` and `gmock` targets.
Here is a MWE illustrating the workaround:
```auto
cmake_minimum_required(VERSION 3.25)
project(gtest-tidy-mwe)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)
# Set up clang-tidy
find_program(CLANG_TIDY_EXE NAMES clang-tidy PATHS /opt/homebrew/opt/llvm/bin/)
if(NOT CLANG_TIDY_EXE)
message(ERROR "clang-tidy not found. Skipping corresponding checks.")
else()
set(CMAKE_CXX_CLANG_TIDY
${CLANG_TIDY_EXE};
-header-filter=.;
-checks=-*,portability-*,bugprone-*,readability-;
-warnings-as-errors=*)
endif()
# Set up googletest
include(FetchContent)
FetchContent_Declare(
googletest
GIT_REPOSITORY https://github.com/google/googletest.git
GIT_TAG 750d67d809700ae8fca6d610f7b41b71aa161808
SYSTEM
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
# Silence clang-tidy warnings from googletest
set_target_properties(gtest PROPERTIES CXX_CLANG_TIDY "")
set_target_properties(gtest_main PROPERTIES CXX_CLANG_TIDY "")
set_target_properties(gmock PROPERTIES CXX_CLANG_TIDY "")
set_target_properties(gmock_main PROPERTIES CXX_CLANG_TIDY "")
# Create dummy main
file(WRITE ${CMAKE_BINARY_DIR}/gtest-tidy-mwe.cpp
"#include \n"
"TEST(HelloTest, BasicAssertions) {\n"
" EXPECT_EQ(7 * 6, 42);\n"
"}\n"
)
add_executable(gtest-tidy-mwe
${CMAKE_BINARY_DIR}/gtest-tidy-mwe.cpp
)
target_link_libraries(gtest-tidy-mwe PRIVATE GTest::gtest GTest::gtest_main)
```
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [April 19, 2023, 7:51pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/13 "2023-04-19T19:51:53Z")
## It works, but you are expecting to much!
With this `CMakeLists.txt` you compile everything with `clang-tidy`, the **gtest** sources too!
If you build all and check your example source file only, it works as you want:
```bash
/usr/local/opt/llvm/bin/clang-tidy -p=/Users/clausklein/Workspace/cpp/test/cmake-build-test-x86_64-Debug/install /Users/clausklein/Workspace/cpp/test/cmake-build-test-x86_64-Debug/install/gtest-tidy-mwe.cpp
81565 warnings generated.
Suppressed 81622 warnings (81565 in non-user code, 57 NOLINT).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
bash-3.2$
```
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [April 19, 2023, 7:55pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/14 "2023-04-19T19:55:11Z")
```cmake
cmake_minimum_required(VERSION 3.25...3.26)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
project(gtest-tidy-mwe LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)
# Set up clang-tidy
find_program(CLANG_TIDY_EXE NAMES clang-tidy PATHS /opt/homebrew/opt/llvm/bin/)
if(NOT CLANG_TIDY_EXE)
message(ERROR "clang-tidy not found. Skipping corresponding checks.")
else()
set(CLANG_TIDY_CMD_LINE ${CLANG_TIDY_EXE}; -header-filter=.;
-checks=-*,modernize-*,bugprone-*,hicpp-*,performance-*,portability-*,readability-;
-warnings-as-errors=*
)
endif()
# Enable clang-tidy for target
macro(target_enable_clang_tidy TARGET)
set_target_properties(${TARGET} PROPERTIES C_CLANG_TIDY "${CLANG_TIDY_CMD_LINE}")
set_target_properties(${TARGET} PROPERTIES CXX_CLANG_TIDY "${CLANG_TIDY_CMD_LINE}")
endmacro()
# Set up googletest
include(FetchContent)
FetchContent_Declare(
googletest
GIT_REPOSITORY https://github.com/google/googletest.git
GIT_TAG 750d67d809700ae8fca6d610f7b41b71aa161808
SYSTEM
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
# Create dummy main
file(WRITE ${CMAKE_BINARY_DIR}/gtest-tidy-mwe.cpp
"#include \n" "TEST(HelloTest, BasicAssertions) {\n"
" EXPECT_EQ(7 * 6, 42);\n" "}\n"
)
add_executable(gtest-tidy-mwe ${CMAKE_BINARY_DIR}/gtest-tidy-mwe.cpp)
target_link_libraries(gtest-tidy-mwe PRIVATE GTest::gtest GTest::gtest_main)
# enable clang-tidy for my target only!
target_enable_clang_tidy(gtest-tidy-mwe)
enable_testing()
add_test(NAME gtest-tidy-mwe COMMAND gtest-tidy-mwe)
install(TARGETS gtest-tidy-mwe)
include(cpack)
```
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [April 19, 2023, 7:57pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/15 "2023-04-19T19:57:31Z")
P.S: I never set
> [@ClausKlein](#):
>
> `CMAKE_CXX_CLANG_TIDY`
I always set
> [@ClausKlein](#):
>
> ```auto
> set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
>
> ```
---
### Author:  [@tvercaut](https://discourse.cmake.org/u/tvercaut)
#### Post date: [April 19, 2023, 8:17pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/16 "2023-04-19T20:17:22Z")
Many thanks! I figured it out at the same time and edited my previous post.
---
### Author:  [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [April 20, 2023, 12:03am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/17 "2023-04-20T00:03:52Z")
In my [earlier comment](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/9), I only suggested that the `SYSTEM` property could be made to apply to linters, checkers and verification tasks as well, but to my knowledge, there hasn’t been a formal proposal or anyone working on it yet.
---
### Author:  [@anthonya](https://discourse.cmake.org/u/anthonya)
#### Post date: [May 1, 2024, 3:39am UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/18 "2024-05-01T03:39:25Z")
I’ve recently tried this, and I’m pretty sure `run-clang-tidy` is not respecting it. I have multiple projects imported via FetchContent and even with `SYSTEM` they still show up in my clang-tidy run.
---
### Author:  [@ClausKlein](https://discourse.cmake.org/u/ClausKlein)
#### Post date: [May 2, 2024, 5:25pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/19 "2024-05-02T17:25:06Z")
> [@ClausKlein](#):
>
> ```auto
> # Enable clang-tidy for target
> macro(target_enable_clang_tidy TARGET)
> set_target_properties(${TARGET} PROPERTIES C_CLANG_TIDY "${CLANG_TIDY_CMD_LINE}")
> set_target_properties(${TARGET} PROPERTIES CXX_CLANG_TIDY "${CLANG_TIDY_CMD_LINE}")
> endmacro()
>
> ```
If you mean this, than you are right, That is only to prevent the `pre-compile-step`!
---
### Author:  [@anthonya](https://discourse.cmake.org/u/anthonya)
#### Post date: [May 2, 2024, 6:19pm UTC](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871/20 "2024-05-02T18:19:07Z")
Ah, shame, so that means this won’t work with `run-clang-tidy`?
[Next page](https://discourse.cmake.org/t/how-to-prevent-clang-tidy-to-check-sources-added-with-fetchcontents/2871.md?page=2)