When using the boost MPL library, one can set a define to increase
the limit of how many variadic elements should be supported. The
default for BOOST_MPL_LIMIT_VECTOR_SIZE is 20:
http://www.boost.org/doc/libs/1_36_0/libs/mpl/doc/refmanual/limit-vector-size.html
If the foo library requires that to be set to 30, and the independent
bar library requires it to be set to 40, consumers of both need to set
it to 40.
add_library(foo INTERFACE)
set_property(TARGET foo PROPERTY INTERFACE_boost_mpl_vector_size 30)
set_property(TARGET foo PROPERTY COMPATIBLE_INTERFACE_NUMBER_MAX boost_mpl_vector_size)
target_compile_definitions(foo INTERFACE BOOST_MPL_LIMIT_VECTOR_SIZE=$<TARGET_PROPERTY:boost_mpl_vector_size>)
add_library(bar INTERFACE)
set_property(TARGET bar PROPERTY INTERFACE_boost_mpl_vector_size 40)
# Technically the next two lines are redundant, but as foo and bar are
# independent, they both set these interfaces.
set_property(TARGET bar PROPERTY COMPATIBLE_INTERFACE_NUMBER_MAX boost_mpl_vector_size)
target_compile_definitions(bar INTERFACE BOOST_MPL_LIMIT_VECTOR_SIZE=$<TARGET_PROPERTY:boost_mpl_vector_size>)
add_executable(user)
target_link_libraries(user foo bar)
Because the TARGET_PROPERTY reads the boost_mpl_vector_size property
from the HEAD of the dependency graph (the user target), and because
that property appears in the COMPATIBLE_INTERFACE_NUMBER_MAX of
the dependencies of the user target, the maximum value for it is
chosen for the compile definition, ie, 40.
There are also use-cases for choosing the minimum value of a number.
In Qt, deprecated API can be disabled by version. Setting the
definition QT_DISABLE_DEPRECATED_BEFORE=0 disables no deprecated
API. Setting it to 0x501000 disables API which was deprecated before
Qt 5.1 etc.
If two dependencies require the use of API which was deprecated in
different Qt versions, then COMPATIBLE_INTERFACE_NUMBER_MIN can be
used to ensure that both can compile.
If you think about adding a new testcase then here is a small checklist you
can run through to find a proper place for it. Go through the list from the
beginning and stop once you find something that matches your tests needs,
i.e. if you will test a module and only need the configure mode use the
instructions from section 2, not 3.
1. Your testcase can run in CMake script mode, i.e. "cmake -P something"
Put your test in Tests/CMakeTests/ directory as a .cmake.in file. It will be
put into the test binary directory by configure_file(... @ONLY) and run from
there. Use the AddCMakeTest() macro in Tests/CMakeTests/CMakeLists.txt to add
your test to the test runs.
2. Your test needs CMake to run in configure mode, but will not build anything
This includes tests that will build something using try_compile() and friends,
but nothing that expects add_executable(), add_library(), or add_test() to run.
If the test configures the project only once and it must succeed then put it
into the Tests/CMakeOnly/ directory. Create a subdirectory named like your
test and write the CMakeLists.txt you need into that subdirectory. Use the
add_CMakeOnly_test() macro from Tests/CMakeOnly/CMakeLists.txt to add your
test to the test runs.
If the test configures the project with multiple variations and verifies
success or failure each time then put it into the Tests/RunCMake/ directory.
Read the instructions in Tests/RunCMake/CMakeLists.txt to add a test.
3. If you are testing something from the Modules directory
Put your test in the Tests/Modules/ directory. Create a subdirectory there
named after your test. Use the ADD_TEST_MACRO macro from Tests/CMakeLists.txt
to add your test to the test run. If you have put your stuff in
Tests/Modules/Foo then you call it using ADD_TEST_MACRO(Module.Foo Foo).
4. You are doing other stuff.
Find a good place ;) In doubt mail to cmake-developers@cmake.org and ask for
advise.
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