failed recompaction: Permission denied

[Selviniahh]

I only get this error failed recompaction: Permission denied if I want to force running cmake twice. Here's my minimal cmake file and the minimal project itself

untitled.zip

project(untitled)
set(CMAKE_CXX_STANDARD 20)

# Increment counter
file(READ "${CMAKE_SOURCE_DIR}/Counter.txt" COUNTER)
MATH(EXPR COUNTER "${COUNTER}+1")
file(WRITE "${CMAKE_SOURCE_DIR}/Counter.txt" "${COUNTER}")

add_executable(untitled main.cpp)
# Create a custom target to run CMake again
add_custom_command(TARGET untitled POST_BUILD
        COMMAND cmake CMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} CMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
        CMAKE_C_COMPILER=${CMAKE_C_COMPILER} CMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -G "${CMAKE_GENERATOR}"
        -S ${CMAKE_SOURCE_DIR} -B ${CMAKE_BINARY_DIR})

message(${CMAKE_COMMAND})

ninja's output with -v note that, with MinGW and native ninja on windows, it's same.

FAILED: untitled.exe 
C:\WINDOWS\system32\cmd.exe /C "cd . && C:\msys64\clang64\bin\clang++.exe -g  CMakeFiles/untitled.dir/main.cpp.obj -o untitled.exe -Wl,--out-implib,libuntitled.dll.a -Wl,--major-image-version,0,--minor-image-version,0  -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 && C:\WINDOWS\system32\cmd.exe /C "cd /D C:\Users\xqwys\CLionProjects\untitled\cmake-build-debug-mingw-clang && C:\Users\xqwys\AppData\Local\Programs\CLion\bin\cmake\win\x64\bin\cmake.exe -G Ninja -S C:/Users/xqwys/CLionProjects/untitled -B C:/Users/xqwys/CLionProjects/untitled/cmake-build-debug-mingw-clang""
C:/Users/xqwys/AppData/Local/Programs/CLion/bin/cmake/win/x64/bin/cmake.exe
-- Configuring done (0.2s)
-- Generating done (0.0s)
CMake Error:
  Running

   'C:/msys64/mingw64/bin/ninja.exe' '-C' 'C:/Users/xqwys/CLionProjects/untitled/cmake-build-debug-mingw-clang' '-t' 'recompact'

  failed with:

   ninja: error: failed recompaction: Permission denied



CMake Error:
  Running

   'C:/msys64/mingw64/bin/ninja.exe' '-C' 'C:/Users/xqwys/CLionProjects/untitled/cmake-build-debug-mingw-clang' '-t' 'restat' 'build.ninja'

  failed with:

   ninja: error: failed recompaction: Permission denied



CMake Generate step failed.  Build files cannot be regenerated correctly.
ninja: build stopped: subcommand failed.```

[Selviniahh]

Today I just realized every time I get the same error at first try and when I just try to build the intermediates again WITHOUT DOING ANYTHING it just works, yeah that's all It's just works.

I made a video: https://www.youtube.com/watch?v=weA4eTKaESU

[digit-google]

Let me get this straight: your CMakeList.txt generates a Ninja build plan which contains a build rule/action that invokes CMake during the build (i.e. while Ninja is running). This CMake invocation is calling Ninja with -t recompact. The process tree should look like:

cmake --build <build_dir>
   |
   |____ ninja -C <build_dir>
             |
             |__ cmake -B <build_dir>
                    |
                    |___ ninja -C <build_dir> -t recompact

The recompact operation is trying to remove or truncate the build log (to replace it with new content), but this fails because the top-level ninja process still has an opened handle on that file.

On Windows, it is not possible to delete a file if another process still has a handle on it (it is possible on Posix).
This is why your are seeing a permission issue here.

I am curious to know why you would need to run CMake at build time, since Ninja already supports re-running the generator (CMake here) when needed. But what you see is not a Ninja issue, rather that neither Ninja nor CMake are designed to support this use case.

[Selviniahh]

@digit-google Hi, thanks for reply. I made profile guided optimization with clang with -fprofile-instr-generate option, this will generate profraw files and I have to manually merge and then recompile cmake with using the merged profile file. I wanted to automate this process however I need a way to make CMake somehow act like a file has changed so it can rerun the script without clearing the build system. Since CMake doesn't care changes in binary build folder, I have to manually add a file in source dir or change something in my source.

The solution was just write this

    file(GLOB_RECURSE MYFILE LIST_DIRECTORIES true CONFIGURE_DEPENDS ${CMAKE_BINARY_DIR}/bin/*)

However, there's no mention of this solution anywhere on the internet, nor did AI help. I had to read the documentation. I should open a thread in the CMake forum and mentioned this solution. Let's not close this issue as it could be helpful in the future.