CMake FetchContent Difficulties

[TheFloatingBrain]

Im trying to use Ogre-Next with CMake Fetch Content, I have attached my CMakeLists.txt.
I am using windows with msbuild generator (one of my dependencies tried to pass $(TargetConfiguration) or something like that to ninja).

Presently I am noticing some issues, the first one is that it seems to be pulling an extremely out of date LibRaw Datastream which still contained the infamous deprecated std::auto_ptr which because it detracted is causing compiler errors.

The second, which may be caused by the first is I am getting something wrong when following the shaderc.rule, first it tells me Error D8040 error creating or communicating with child process
Which is followed by

Error MSB8066 Custom build for 'REDACT\out\build\x64-debug\CMakeFiles\REDACT\shaderc-build.rule;
.. REDACT\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets	254

Followed by two

Error C1083 Cannot open compiler generated file: '': Invalid argument REDACT\out\build\x64-debug\_deps\ogre-next-deps-src\src\vulkan\shaderc\src\third_party\spirv-tools\source\reduce\conditional_branch_to_simple_conditional_branch_reduction_opportunity.cpp

shaderc appears to be a dpendancy in ogre-next-deps that something fails in which may or may not be related to the error in LibRaw Datastream which appears to need a 1 in front of its version number instead of a 0.

I'd like to avoid the .bat scripts (because I just want to keep everything working with FetchContent) but I did reference them when composing this CMakeLists.txt file

Anyone have any idea what is going on or how I can fix it? I have a feeling something is getting misinterpreted like a version number or something unusual is happening causing a bug with the version number of LibRaw Datastream or something. Not sure.

Thanks!

• TFB

[darksylinc]

Hi!

I have no experience with the fetch command so I cannot help much.

Anyone have any idea what is going on or how I can fix it? I have a feeling something is getting misinterpreted like a version number or something unusual is happening causing a bug with the version number of LibRaw Datastream or something. Not sure.

Try using ExternalProject_Add instead which will let you run CMake like if it were a *.bat script.

We do that for SDL whose CMake scripts were so complex it was impossible to add them the regular way without breaking something.

I'd like to avoid the .bat scripts (because I just want to keep everything working with FetchContent)

This is my personal opinion and it will feel hypocrite considering how insanely complex OgreNext CMake scripts are (which is mostly because of historical reasons as were one of the first projects to adopt CMake), but CMake is a horrible language that is great at doing its job.

You'll get the best bang for your buck if you keep your CMake script as simple as possible (basically as close as a "Hello World" as possible where you define the headers, the source files, include headers, linked libraries, and the compiler settings. That's it). Then everything else (like downloading repository dependencies and setting them up) is handled by a better script language like Python or even *.bat / bash scripts.

This will also make your iteration times faster as tying dependency fetching to your CMake scripts means CMake must reparse them every time you need to rebuild.

[TheFloatingBrain]

Hey thank you, I have gotten to about the same place however I'm still getting include errors for Freeimage.h, even when I try to manually specify the include directory

cmake_minimum_required(VERSION 3.28)
project(PhysicsBlockGame CXX)
set(CMAKE_CXX_STANDARD 23)
include(FetchContent)
include(ExternalProject)

if(WIN32)
	set(CMAKE_GENERATOR "Visual Studio 17 2022")
endif()

set(OGRE_CONFIG_THREAD_PROVIDER 0)
set(OGRE_CONFIG_THREADS 0)
set(OGRE_BUILD_COMPONENT_SCENE_FORMAT 1)
set(OGRE_BUILD_SAMPLES2 0)
set(OGRE_BUILD_TESTS 0)
set(OGRE_NEXT_PREFIX "C:\\Libraries")
set(OGRE_DEPENDENCIES_DIR OGRE_NEXT_PREFIX/src/Ogre-Next-Deps-build/ogredeps)
include_directories(${OGRE_DEPENDENCIES_DIR} ${OGRE_DEPENDENCIES_DIR}/src/Ogre-Next-Deps/src/FreeImage/Source)
message("Fetched Ogre-Next-Deps")
make_directory(${OgreNextDepsSourceDir}/build)

ExternalProject_Add(
	"Ogre-Next-Deps"
	GIT_REPOSITORY "https://github.com/OGRECave/ogre-next-deps"
	GIT_TAG "master"
	GIT_PROGRESS TRUE
	GIT_SUBMODULES_RECURSE TRUE
	GIT_SHALLOW TRUE
	PREFIX ${OGRE_NEXT_PREFIX}
	#SOURCE_DIR ${OgreNextDepsSourceDir}
)

ExternalProject_Add(
	"Ogre-Next"
	GIT_REPOSITORY "https://github.com/OGRECave/ogre-next"
	GIT_TAG "master"
	GIT_PROGRESS TRUE
	PREFIX ${OGRE_NEXT_PREFIX}
)

file(GLOB SCRATCHPAD_SOURCE scratchpad/*.cpp)
add_executable(scratchpad ${SCRATCHPAD_SOURCE})
set_property(TARGET scratchpad PROPERTY CXX_STANDARD 23)