On 12/08/2016 04:01 PM, Robert Dailey wrote:
When I define my targets (custom, library, executable), does the order
of their declaration matter when it comes to using those targets in
dependencies? It's difficult to explain, so I'll show an example:
add_executable(foo main1.cpp)
target_link_libraries(foo abc)
add_library(abc main2.cpp)
In the example above, the add_library() happens after
target_link_libraries() for the executable. I've seen this work, but I
was using static libraries. Would this work for shared libraries too?
Yes, that is fine.
Does CMake do a multi-pass parse so that all targets are known prior
to them being referenced?
The link-dependencies are evaluated at generation time after your cmake
code has been fully parsed.
At that time all targets are known.
The target_link_libraries() [1] documentation states:
"The named target must be created by add_library() within the project
or as an IMPORTED library. If it is created within the project an
ordering dependency will automatically be added in the build system to
make sure the named library target is up-to-date before the <target>
links."
I'm not sure what "up-to-date" here means, or if this specific
documentation is talking about compile-time dependencies or cmake
dependencies.
It means CMake makes sure the generated build system fully builds "abc"
before it starts building "foo" (which isn't always strictly required
but how it is currently implemented).
e.g. if "abc" has custom commands that generate header files that "foo"
also depends on this will make sure they are created/updated before
"foo" makes use of them.
And more obviously "abc"'s library output is created/updated before
"foo" tries to link to it.
Nils
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