# On Windows CHECK\_CXX\_SOURCE\_RUNS is calling check\_source\_runs

**URL:** https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065
**Category:** Code
**Tags:** os:windows
**Created:** [October 24, 2020, 12:30pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065 "2020-10-24T12:30:28Z")
**Posts on this page:** 13
**Page:** 1

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 24, 2020, 12:30pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/1 "2020-10-24T12:30:28Z")

</div>

I have a very simple project that indicate that when in Windows (Linux) CMAKE\_CXX\_SOURCE\_RUNS is calling (is not calling) my macro check\_source\_runs. The commands

```
mkdir build
cd build
cmake ..

```

run fine on Linux and exit with an error in Windows. The error is the FATAL\_ERROR in the check\_soruce\_runs macro. I am using a Visual Studio 2019 command shell to run cmake on windows.

Here is my CMakeLIsts.txt file:

```
PROJECT(test)
CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
INCLUDE(CheckCXXSourceRuns)
INCLUDE( check_source_runs.cmake )
SET(source_code "
int main(void)
{ return 0; 
}")
CHECK_CXX_SOURCE_RUNS( "${source_code}" flag )

```

Here is my file check\_source\_runs.cmake

```
MACRO( check_source_runs )
    MESSAGE(FATAL_ERROR "The check_source_runs macro is being called by CHECK_CXX_SOURCE_RUNS")
ENDMACRO( check_source_runs )
```

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 24, 2020, 9:37pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/2 "2020-10-24T21:37:14Z")

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Cc: @robert.maynard

Can you confirm the CMake version that gets invoked on Windows and on Linux? Have your project actually print it by adding the following line:

```cmake
message("CMake version = ${CMAKE_VERSION}")

```

I can’t think of a reason why the behavior would be different between platforms (assuming no subtle bug to do with case sensitivity of the file system making a difference).

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 24, 2020, 9:40pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/3 "2020-10-24T21:40:22Z")

</div>

As an aside, the `cmake_minimum_required()` command should come before the call to `project()`. The `cmake_minimum_required()` command sets some policies that will/should affect the call to `project()`.

---

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 24, 2020, 10:10pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/4 "2020-10-24T22:10:29Z")

</div>

I kept CMakeLists.txt and check\_source\_runs.cmake the same, I just added a request for the cmake version on the command line. Here is the verbose output on Linux:  
if [-e build]  
then  
rm -r build  
fi  
mkdir build  
cd build  
cmake --version  
cmake version 3.14.5

```
CMake suite maintained and supported by Kitware (kitware.com/cmake).
cmake ..
-- The C compiler identification is GNU 9.2.1
-- The CXX compiler identification is GNU 9.2.1
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test flag
-- Performing Test flag - Success
-- Configuring done
-- Generating done
-- Build files have been written to: /home/bradbell/trash/cmake_bug/build
cd ..
rm -r build
#
echo 'run.sh: OK'
run.sh: OK
exit 0

```

Here is the verbose output on Windows:  
C:\msys64\home\bradl\trash\cmake\_bug\>IF EXIST build RMDIR /S /Q build  
C:\msys64\home\bradl\trash\cmake\_bug\>MKDIR build  
C:\msys64\home\bradl\trash\cmake\_bug\>CD build  
C:\msys64\home\bradl\trash\cmake\_bug\build\>cmake --version  
cmake version 3.19.0-rc1  
CMake suite maintained and supported by Kitware ([kitware.com/cmake](http://kitware.com/cmake)).  
C:\msys64\home\bradl\trash\cmake\_bug\build\>cmake …  
– Building for: Visual Studio 16 2019  
– Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.18363.  
– The C compiler identification is MSVC 19.27.29112.0  
– The CXX compiler identification is MSVC 19.27.29112.0  
– Detecting C compiler ABI info  
– Detecting C compiler ABI info - done  
– Check for working C compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.27.29110/bin/Hostx64/x64/cl.exe - skipped  
– Detecting C compile features  
– Detecting C compile features - done  
– Detecting CXX compiler ABI info  
– Detecting CXX compiler ABI info - done  
– Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Community/VC/Tools/MSVC/14.27.29110/bin/Hostx64/x64/cl.exe - skipped  
– Detecting CXX compile features  
– Detecting CXX compile features - done  
CMake Error at check\_source\_runs.cmake:2 (MESSAGE):  
The check\_source\_runs macro is being called by CHECK\_CXX\_SOURCE\_RUNS  
Call Stack (most recent call first):  
C:/Program Files/CMake/share/cmake-3.19/Modules/CheckCXXSourceRuns.cmake:71 (check\_source\_runs)  
CMakeLists.txt:9 (CHECK\_CXX\_SOURCE\_RUNS)

```
-- Configuring incomplete, errors occurred!
See also "C:/msys64/home/bradl/trash/cmake_bug/build/CMakeFiles/CMakeOutput.log".
C:\msys64\home\bradl\trash\cmake_bug\build>cd .. 
C:\msys64\home\bradl\trash\cmake_bug>RMDIR /S /Q build 
C:\msys64\home\bradl\trash\cmake_bug>REM
C:\msys64\home\bradl\trash\cmake_bug>ECHO 'run.bat: OK' 
'run,bat: OK'
```

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 24, 2020, 10:24pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/5 "2020-10-24T22:24:43Z")

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You are using different CMake versions on the two different platforms. The 3.19 release is the first one where `check_cxx_source_runs()` forwards to `check_source_runs()`. This is why you are not seeing your `check_source_runs()` macro being invoked on Linux, since you are only running 3.14 there. I [posted just yesterday](https://discourse.cmake.org/t/cleaning-up-check-lang-sourcecompiles-module-docs/2063) about updating the 3.19 docs for these modules, which I suspect would make situations like this a bit clearer.

---

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 24, 2020, 11:07pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/6 "2020-10-24T23:07:40Z")

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So this is a change to to API for check\_cxx\_source\_runs; i.e., it is not backward compatible ?

I would expect the major version of cmake to change when the API was no longer backward compatible. Are there at least release notes that list all of these sort of changes ?

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 25, 2020, 1:33am UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/7 "2020-10-25T01:33:59Z")

</div>

No it is not an API change. The original API of the commands from the various `Check<Lang>SourceRuns` modules should still be honoured. What seems to be the case here is you are trying to use an implementation detail of the new module introduced in CMake 3.19 and expect it to work with an older CMake version. You should also not be trying to hijack the `check_source_runs()` command by replacing it with your own.

---

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 25, 2020, 2:22am UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/8 "2020-10-25T02:22:08Z")

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I am not trying to use the implementation detail. My original check\_source\_runs macro was a wrapper for CHECK\_CXX\_SOURCE\_RUNS. I do not see any mention in  
[https://cmake.org/cmake/help/latest/module/CheckCXXSourceRuns.html](https://cmake.org/cmake/help/latest/module/CheckCXXSourceRuns.html)  
of the fact that the name check\_source\_runs cannot be used for such a purpose.

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [October 25, 2020, 2:30am UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/9 "2020-10-25T02:30:38Z")

</div>

Ok if it was a command that you were already using before CMake 3.19, then that is relevant. @robert.maynard Do we have a way to handle this scenario?

---

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 25, 2020, 10:33am UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/10 "2020-10-25T10:33:25Z")

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Yes. I have changed its name from check\_source\_runs to run\_source\_test.

When I do something like this in my software, I put an **API Change** notice in my release notes and identify the exact version where it changed.

---

<div class="post-metadata">

### Author: ![bradbell](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/e95f7d/32.png) [@bradbell](https://discourse.cmake.org/u/bradbell)
#### Post date: [October 25, 2020, 10:51am UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/11 "2020-10-25T10:51:57Z")

</div>

By the way, all my old release of my software will no longer install with cmake at or after version 3.19.

---

<div class="post-metadata">

### Author: ![robert.maynard](https://discourse.cmake.org/user_avatar/discourse.cmake.org/robert.maynard/32/4_2.png) [@robert.maynard](https://discourse.cmake.org/u/robert.maynard)
#### Post date: [October 25, 2020, 12:50pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/13 "2020-10-25T12:50:07Z")

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I agree that automatic capture of the `check_source_runs` names without explicit opt-in by including the name `CheckSourceRuns` module shouldn’t happen.

I think that we can do is move the implementation to `cmake_check_source_runs` and only have that exposed when including files such as `CheckCXXSourceRuns`. This will better preserve backwards compatibility as CMake reserves all functions starting with `cmake_`.

I should have time this week to open a merge request to fix this.

---

<div class="post-metadata">

### Author: ![robert.maynard](https://discourse.cmake.org/user_avatar/discourse.cmake.org/robert.maynard/32/4_2.png) [@robert.maynard](https://discourse.cmake.org/u/robert.maynard)
#### Post date: [October 25, 2020, 8:09pm UTC](https://discourse.cmake.org/t/on-windows-check-cxx-source-runs-is-calling-check-source-runs/2065/14 "2020-10-25T20:09:59Z")

</div>

@bradbell

You can track the progress on correcting this regression at:  
[https://gitlab.kitware.com/cmake/cmake/-/issues/21359](https://gitlab.kitware.com/cmake/cmake/-/issues/21359)