On 29-Jan-16 01:17, Stephen Kelly wrote:
Pau Garcia i Quiles wrote:
add_subdirectory(pugixml/scripts)
add_subdirectory(QtZeroConf)
add_subdirectory(QtDropBox)
add_subdirectory(websocketpp)
This is an easy way to work with third-party dependences.
Unfortunately this is 'easy, obvious and wrong'.
This is wrong because of CMake limitations. Actually I was thinking
about "namespacing" subdirectories too. From my point of view we can add
namespace prefix every time when command 'project' called.
Project Foo:
== standalone ==
project(Foo)
add_library(foo ...) # add target foo
== as a subdirectory ==
project(Boo)
add_subdirectory(Foo)
# target Foo::foo
Since regular variables has different scope there is no need to do any
updates for them, we need only to do something with globals: targets,
cache variables, global properties (?).
My problem comes from the fact several of these third-party libraries use
common variable names, e. g. BUILD_SHARED, BUILD_TESTS, etc).
And indeed this is why.
Has some kind of namespacing been considered for add_subdirectory?
E. g.
add_subdirectory(QtZeroConf NAMESPACE QTZEROCONF)
And what if someone builds your project with -DBUILD_SHARED=ON? Are you
going to use
set(QTZEROCONF_BUILD_SHARED ${BUILD_SHARED})
add_subdirectory(QtZeroConf NAMESPACE QTZEROCONF)
for every variable you're wrapping? Or do you want cmake to do that for
every variable in scope when the directory is added? How would cmake decide
which variables to namespace?
I think this can be solved by adding extra suboptions to
add_subdirectory command.
You should use ExternalProject instead, or fork the buildsystem of those
projects to integrate them into your project. Not that I recommend the
latter for you though :). That's what cmake does when integrating 3rd party
code.
As far as I understand `add_subdirectory(3rdParty/package)` approach
used in CMake sources:
* zlib:
https://github.com/Kitware/CMake/blob/5335d275527d4f58e4f2992d307c1c62cd94dd3c/CMakeLists.txt#L306
* curl:
https://github.com/Kitware/CMake/blob/5335d275527d4f58e4f2992d307c1c62cd94dd3c/CMakeLists.txt#L337
* bzip2:
https://github.com/Kitware/CMake/blob/5335d275527d4f58e4f2992d307c1c62cd94dd3c/CMakeLists.txt#L355
Ruslo
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