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.
This target type only contains INTERFACE_* properties, so it can be
used as a structural node. The target-specific commands enforce
that they may only be used with the INTERFACE keyword when used
with INTERFACE_LIBRARY targets. The old-style target properties
matching LINK_INTERFACE_LIBRARIES_<CONFIG> are always ignored for
this target type.
The name of the INTERFACE_LIBRARY must match a validity generator
expression. The validity is similar to that of an ALIAS target,
but with the additional restriction that it may not contain
double colons. Double colons will carry the meaning of IMPORTED
or ALIAS targets in CMake 2.8.13.
An ALIAS target may be created for an INTERFACE library.
At this point it can not be exported and does not appear in the
buildsystem and project files are not created for them. That may
be added as a feature in a later commit.
The generators need some changes to handle the INTERFACE_LIBRARY
targets returned by cmComputeLinkInterface::GetItems. The Ninja
generator does not use that API, so it doesn't require changes
related to that.
These interface-related link-libraries properties are used to determine
the value of the other INTERFACE properties, so we were getting infinite
recursion and segfaults otherwise.
Stephen Kelly
Andreas Mohr