[CMake] Passthrough variables for packages to subbuilds #107611
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These packaged are imported by LLVMConfig.cmake and so we should be passing through the necessary variables from the parent build into the subbuilds. We use `CMAKE_CACHE_DEFAULT_ARGS` so subbuilds can override these variables if needed.
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Do you happen to know which order CMake passes in the -C arg for CMAKE_CACHE_DEFAULT_ARGS vs. the arguments inside CMAKE_ARGS? If the -C goes before CMAKE_ARGS (which I suspect), there's a potential interaction with https://reviews.llvm.org/D158791; if you want to use that mechanism to override any of these variables, you'll have to specify FORCE. That's fine, just something that came to mind.
| get_property(is_value_set CACHE ${variable} PROPERTY VALUE SET) | ||
| if(${is_value_set}) | ||
| get_property(value CACHE ${variable} PROPERTY VALUE) | ||
| list(APPEND CMAKE_CACHE_DEFAULT_ARGS "-D${variable}:STRING=${value}") |
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Do we not need to replace ; with | to have list variables be passed through correctly? The documentation isn't clear on whether LIST_SEPARATOR applies to CMAKE_CACHE_DEFAULT_ARGS.
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That's what I read as well but I wasn't sure if it's needed or not so I tested and it looks like it's not required.
The following example:
ExternalProject_Add(test
SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/test
CMAKE_ARGS -Done=a|b|c
CMAKE_CACHE_ARGS -Dtwo:STRING=a;b;c
CMAKE_CACHE_DEFAULT_ARGS -Dthree:STRING=a|b|c
LIST_SEPARATOR |
)produces the following cache file:
set(two "a;b;c" CACHE STRING "Initial cache" FORCE)
set(three "a;b;c" CACHE STRING "Initial cache" )
It looks like the |
These packaged are imported by LLVMConfig.cmake and so we should be passing through the necessary variables from the parent build into the subbuilds.
We use
CMAKE_CACHE_DEFAULT_ARGSso subbuilds can override these variables if needed.