Make NVTX CMake relocatable.

[bdice]

This resolves #113.

I added a config and targets file, using the existing logic in CMakeLists.txt and nvtxImportedTargets.cmake. I tried to modify these files in a way that wouldn't break existing uses of the CMake code (which apparently only works via add_subdirectory).

I tested these changes with:

mkdir -p /tmp/nvtx-install
mkdir -p c/build

pushd c/build
rm -rf * && rm -rf /tmp/nvtx-install/* && cmake .. -DCMAKE_INSTALL_PREFIX=/tmp/nvtx-install && cmake --build . && cmake --install .
popd

mkdir -p c/examples/build

pushd c/examples/build
rm -rf * && cmake .. -DCMAKE_PREFIX_PATH=/tmp/nvtx-install && cmake --build .
popd

I think the NVTX relocatable install in /tmp/nvtx-install looks like it should work, based on my knowledge of how rapids-cmake works (https://github.com/rapidsai/rapids-cmake/blob/branch-25.04/rapids-cmake/cpm/nvtx3.cmake). The example code builds and runs with the appropriate include directories.

To move this PR forward, this may need some or all of the following:

• Better CMake test code in CI, perhaps this can be done in a separate PR prior to merging this PR. The current code in c/examples should probably be in a directory of CMake tests somewhere.
• Some kind of documentation changes? The NVTX docs appear to live in several places.
• Review from two of the RAPIDS CMake folks: @robertmaynard, @vyasr, @KyleFromNVIDIA
• Review from NVTX maintainers

[robertmaynard]

All the install rules should be guarded behind a check that looks like:

set(NVTX3_IS_ROOT_PROJECT .....)
option(NVTX3_INSTALL ${NVTX3_IS_ROOT_PROJECT})
if(NVTX3_INSTALL)
....
endif()

That way existing projects don't start installing nvtx3 where previously they didn't.

[bdice]

I guessed that the ..... was supposed to be this condition:

set(NVTX3_IS_ROOT_PROJECT "${CMAKE_SOURCE_DIR}" STREQUAL "${PROJECT_SOURCE_DIR}")

If that's correct, I think this is fixed.

[robertmaynard]

You can use PROJECT_IS_TOP_LEVEL https://cmake.org/cmake/help/latest/variable/PROJECT_IS_TOP_LEVEL.html

If we can rely on CMake 3.21 otherwise you generally check CMAKE_PROJECT_NAME matches our project name ( PROJECT_NAME )

[evanramos-nvidia]

@bdice: Thanks for taking this on.

@robertmaynard: Thanks for giving feedback.

We may need to adjust tests/CMakeLists.txt based on your improvements so that our CI passes. I'm not sure if there are ways that file and directory should make more idiomatic use of CMake. The one thing I want to avoid is users building the tests by mistake when they just want to use NVTX in their own project.

[dominik-wojt-2311446]

I was half way trying to do the same at my end. The lack of proper cmake scripts for find_package is really annoying.

Your work is really appreciated.

You might want to add this snippet to README.md:

## Use installed version of NVTX

If NVTX is installed in your system, you can use it with a standard `find_package` procedure.

```cmake
find_package(nvtx3 REQUIRED)

add_executable(some_c_program main.c)
target_link_libraries(some_c_program PRIVATE nvtx3::nvtx3-c)

add_executable(some_cpp_program main.cpp)
target_link_libraries(some_cpp_program PRIVATE nvtx3::nvtx3-cpp)
```

[dominik-wojt-2311446]

I am afraid cmake will not accept the if syntax with set. At least version 3.22.1 I tried it with did not.
This fixed the issue at my end:

if("${CMAKE_SOURCE_DIR}" STREQUAL "${PROJECT_SOURCE_DIR}")
    set(NVTX3_IS_ROOT_PROJECT TRUE)
else()
    set(NVTX3_IS_ROOT_PROJECT FALSE)
endif()

[robertmaynard]

You are correct. CMake doesn't support the original syntax.

I would use:

set(NVTX3_IS_ROOT_PROJECT FALSE)
if("${CMAKE_SOURCE_DIR}" STREQUAL "${PROJECT_SOURCE_DIR}")
    set(NVTX3_IS_ROOT_PROJECT TRUE)
endif()

[dominik-wojt-2311446]

I think this line should be moved to CMakeLists.txt and protected with NVTX3_INSTALL.
It fails when OPTIONALLY_IMPORTED is IMPORTED.

[BwL1289]

@bdice thank you for working on this. We currently can't properly use nvtx in downstream packages (like torch) without this PR.

[bdice]

@dominik-wojt-2311446 @BwL1289 Thanks! I will finish this up shortly.