Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Elizabeth A. Fischer]

Well, I tried upstreaming the new build scripts to some projects and it
didn’t go well.
Some of the reasons I’ve heard of:

> I installed CMake 2.8.6 five years ago and I don’t want to update yet
> again!  People relying on old versions is quite common and any attempt
> to raise the min version will be frowned upon (see the discussion in
> the LLVM mailing lists for example).

Spack is really good at installing dependencies, and makes this a LOT
easier.  In your Spack recipe, you just tell it which version of CMake
your package needs.  If Spack hasn't already built that
version, it will download and install it for you.  Building packages by
hand, and configuring their dependencies, needs to go the way of stone
spears.

> We prefer to use autotools and don’t want to have to learn CMake.
> That’s fair. But also, no one likes to build an autotools backed
> project for Android or iOS.

I suppose it's fair.  But a Google search of "convert CMake to
Autotools" results in 9:1 stories of people abandoning Autotools for
CMake.  Except for the fact that it works well for users, I can't say
enough evil things about Autotools.

Part of the benefit of Autotools is it "just works" without
requiring the user to install anything.  This benefit is of little
value once you move to an auto-builder like Spack.  The days when
you can get any interesting software to work without installing
a zillion dependencies first are long gone.

> I’ve never heard of Spack before. It looks better than other solutions
> I’ve seen before.

The great and unique thing about Spack is it can install a zillion versions
of each package.  For example... if Package B uses MPI, I can build B-1.7
two (or more) times --- once with OpenMPI and once with MPICH.  And I can
install them side-by-side.  If you change any of the dependencies of a
package, Spack will see that as a new and separate version.  Most
auto-builders let you build one software distro, with only one build of
each package (or sometimes one build per numerical version of the package
or compiler or something).  Spack's versioning is a lot more powerful.

> But you still have to manage all the options from your build script

Not sure what you mean by this.  True, there is some redundancy building
code.  First you put the options and dependencies in a package's CMake
build.  And then you put them into the Spack build again.  Some things
could be simplified if we assumed our CMake-based packages would only ever
be built with Spack.  But we still need to create CMake-based software that
can be installed by hand.  Hence the redundancy between the CMake build
scripts and the Spack package.  In practice, this has not been the
end of the world.

Another nice thing about Spack is there is no difference between your
libraries and Third-party libraries.

> and publish the binaries somewhere.

In its original incarnation, Spack builds from source.  It does not publish
or install from binary distros (because the build you asked for, with all
its dependency variants, is likely not a build that's ever been built
before).  There's currently work on a project to use Spack to produce
binary RPMs, and maybe other forms of binary distribution.

> Then you need to teach your build scripts to get the right version.

Your build scripts know nothing about Spack.  Spack is an auto-builder that
sits ON TOP of your build scripts.

> I won’t trade my builds from source for a set of prebuilt binaries
anytime soon I think :)

Spack builds from source, it is not prebuilt binaries.

> > I don't think CMake is the best place to do it,
> Can you provide any details? I personally think that CMake is a
> natural and the only place where it should be done.

The most important reason here is because there are combinatorially
many versions of a package you COULD install, depending on what
versions of its dependencies you link with, and CMake provides nothing
to address that issue.  See here for an overview of how Spack
addresses the combinatorial versioning issue (which no other
auto-builder does, to the best of my knowledge):

http://hpcugent.github.io/easybuild/files/SC14_BoF_Spack.pdf

Once you've built something, it's nice to be able to re-use it.  If I
have a top-level CMake project that automatically builds three
dependencies, will other projects be able to make use of those
dependencies I've built?  Or do they become private?  If libraries
cannot be shared between applications, you will get a LOT of library
bloat, especially among the low-level libraries that get repeated
numerous times.  Admittedly, this may not be such an issue in some
environments where people are really only focused on building one
thing.

If you make a project, you might see it as a "top-level" project.  But
someone else might want to build something bigger on top of your work.  You
can never assume that "this package is top-level and no one will ever
depend on it."

Another obvious problem with using CMake for everything is that not
all packages c

Re: [CMake] Private dependencies of static libraries exported as targets

[Nicholas Braden]

Ah, I misunderstood what you were asking about. It would be pretty
weird if CMake didn't know that static libraries always need all their
dependencies linked regardless of privacy, but I agree it should at
least be mentioned somewhere. My bad.

As for include path bloat, I cannot replicate this in my test project
- CMake will link all the dependencies as required but will NOT
violate "PRIVATE" for other things like include directories. Could you
give an example where you are seeing a static library's private
dependency's include path being added when linking the static library?

On Tue, Aug 16, 2016 at 7:44 PM, Ivan Shapovalov  wrote:
> TBH, I do not see the "PRIVATE dependencies are made PUBLIC for the
> purposes of linking when the dependent is static library" there.
>
> --
> Ivan Shapovalov / intelfx /
>
>
> On 2016-08-16 at 02:35 -0500, Nicholas Braden wrote:
>> Yes, the behavior is documented in several places, the most prominent
>> being here:
>> https://cmake.org/cmake/help/latest/manual/cmake-buildsystem.7.html#t
>> ransitive-usage-requirements
>>
>>
>> On Mon, Aug 15, 2016 at 9:22 PM, Ivan Shapovalov > e> wrote:
>> >
>> > On 2016-08-15 at 21:46 -0400, Guillaume Dumont wrote:
>> > >
>> > > As far as I know the PRIVATE
>> > > keyword
>> > > should have no effect on transitive linking when foo is static
>> > > and we
>> > > call:
>> > >
>> > > target_link_libraries(foo PRIVATE bar)
>> > >
>> > > Hope this helps.
>> >
>> > Wow. I did not know that. Should've tested on sample project.
>> > It does not solve include path bloat though, but that's a minor
>> > issue.
>> >
>> > One question remains... is this behavior documented somewhere?
>> >
>> > Anyway, huge thanks,
>> > --
>> Ivan Shapovalov / intelfx /
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Re: [CMake] Private dependencies of static libraries exported as targets

[Ivan Shapovalov]

TBH, I do not see the "PRIVATE dependencies are made PUBLIC for the
purposes of linking when the dependent is static library" there.

-- 
Ivan Shapovalov / intelfx /


On 2016-08-16 at 02:35 -0500, Nicholas Braden wrote:
> Yes, the behavior is documented in several places, the most prominent
> being here:
> https://cmake.org/cmake/help/latest/manual/cmake-buildsystem.7.html#t
> ransitive-usage-requirements
> 
> 
> On Mon, Aug 15, 2016 at 9:22 PM, Ivan Shapovalov  e> wrote:
> > 
> > On 2016-08-15 at 21:46 -0400, Guillaume Dumont wrote:
> > > 
> > > As far as I know the PRIVATE
> > > keyword
> > > should have no effect on transitive linking when foo is static
> > > and we
> > > call:
> > > 
> > > target_link_libraries(foo PRIVATE bar)
> > > 
> > > Hope this helps.
> > 
> > Wow. I did not know that. Should've tested on sample project.
> > It does not solve include path bloat though, but that's a minor
> > issue.
> > 
> > One question remains... is this behavior documented somewhere?
> > 
> > Anyway, huge thanks,
> > --
> Ivan Shapovalov / intelfx /

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Re: [CMake] Need ideas/opinions on third party library management

[Daniel Schepler]

For what it's worth, what I've done here is to create binary packages of each 
third-party library for each supported platform (i.e. .deb packages for Ubuntu, 
.rpm packages for RHEL/CentOS, Chocolatey packages for Windows).  Except for 
cases where the system already provided sufficient versions of some of the 
libraries.  At the bottom of the internal dependency chain is a base package 
which sets up the infrastructure (e.g. an /etc/profile.d file to add a shell 
function to add entries to CMAKE_PREFIX_PATH, LD_LIBRARY_PATH, etc.) and at the 
top is a set of dependency metapackages, one for each product we have to build. 
 And yes, the middle layer has a combination of large packages like Qt and 
Boost with smaller packages like Expat and SQLite.

Pluses:
- Extremely convenient for an internal developer to just follow a few 
instructions to add our internal repository, then run "apt-get install 
anchorage-exata-deps".
- Similarly convenient for customers developing custom code on top of our code 
if we provide an archive of the required packages, then they can point 
apt/yum/chocolatey to a file: URL.
- It's not too difficult to support installing multiple parallel versions of 
the development environment for different versions of the product - just have 
each one install to a different location, and then the developer selects what 
to use by running the appropriate shell function.
- Greatly simplifies the CMake files for our code, since you just use the 
standard find_package() command (possibly requiring us to write a Find*.cmake 
module).
- Flexibility of being able to easily experiment with a new or custom-compiled 
version of one of the dependencies.
- If an internal developer happens to prefer working on a platform which we 
don't officially support (e.g. Debian testing or Mint), it's generally easy to 
git clone my packaging repositories and build packages for yourself.

Minuses:
- Duplicate packaging work for each different packaging tool when adding a new 
third-party library.
- I haven't yet automated the process of building binary packages and uploading 
to our repository; so when updating any package to a new version (or adding a 
local patch) there's a lot of manual work to do.  (dupload and reprepro help a 
bit for the Ubuntu builds, and nuget has a built-in facility to upload to our 
server; but I haven't found anything similar for the RPM builds.)
- When we do a release and then need to "fork" the repository to a new 
location, it requires a rebuild of all packages at least on Linux.

Overall, most of the pluses apply to everybody, whereas the minuses are just a 
burden on me (or a future maintainer of the repository).  So overall, it's been 
a big improvement over what we used to do, which was to try to maintain binary 
builds of the third-party libraries in SVN.
--
Daniel Schepler
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Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Ruslan Baratov via CMake]

On 16-Aug-16 16:37, Florent Castelli wrote:
Well, I tried upstreaming the new build scripts to some projects and 
it didn’t go well.

Some of the reasons I’ve heard of:
- Windows developpers don’t use CMake, they have project files on the 
repository.

  The CMake files for Windows will never be updated.
They can coexists, it's easier then maintaining forks. If only C++ code 
changed you got new version "for free".


- I installed CMake 2.8.6 five years ago and I don’t want to update 
yet again!
  People relying on old versions is quite common and any attempt to 
raise the min
  version will be frowned upon (see the discussion in the LLVM mailing 
lists for example).
You can add `if(CMAKE_VERSION VERSION_LESS ...)` condition. It's hard to 
support such hairy configuration but anyway.



- We prefer to use autotools and don’t want to have to learn CMake.
  That’s fair. But also, no one likes to build an autotools backed 
project for Android or iOS.
Just for your info Hunter use build scheme for autotools project: 
https://github.com/ruslo/hunter/blob/b4c370e32798cc3da74c37e4156c3bfc77add379/cmake/modules/hunter_autotools_project.cmake
It can create universal iOS libraries and works for Android. There are a 
lot of efforts made by Alexandre Pretyman so this can be possible, it 
has some peculiarities. I guess he can clarify anything if you need details.


Ruslo
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Re: [CMake] Need ideas/opinions on third party library management

[Ruslan Baratov via CMake]

On 13-Aug-16 03:12, Elizabeth A. Fischer wrote:
I don't think CMake is the best place to do it, for a number of 
reasons.  I would not try to re-invent the wheel here.


Can you provide any details? I personally think that CMake is a natural 
and the only place where it should be done.



On 16-Aug-16 15:52, Elizabeth A. Fischer wrote:
But any approach that requires every build to be ported to CMake will 
be difficult and labor-prone to scale.  Writing a meta-build recipe is 
usually much easier.


It is difficult indeed but it's the only way to reach the goal. I have 
kind of a meta-build recipe for the Boost, it was the first non-cmake 
recipe I've added and it's almost 3 year of improvements behind but it's 
still far from what I get in CMake from the box (of course it's not 3 
years of development of just this recipe, but anyway). Just take a look 
at this code:


  add_executable(foo foo.cpp)
  add_library(boo boo.cpp)

With CMake:

   No options: you got executable and static library on host
   BUILD_SHARED_LIBS: you got shared library
   CMAKE_MACOSX_BUNDLE: you got bundle instead of executable
   CMAKE_TOOLCHAIN_FILE=android.cmake: you got library for Android
   CMAKE_TOOLCHAIN_FILE=ios.cmake: you got armv7 library for iOS
   CMAKE_TOOLCHAIN_FILE=ios.cmake + CMAKE_IOS_INSTALL_COMBINED: you got
   armv7 + arm64 + i386 + x86_64 universal library
   /* your toolchain file here */: ...
   Debug: you compile with -O0 for *nix or /Od for MSVC
   MinSizeRel: you compile with -Os for *nix or /O1
   /* your custom build type here */: ...
   Any usage requirements? Propagated AUTOMATICALLY to any project that
   use your library: compiler flags, definitions, dependent libraries, etc.
   Optional dependencies? No problems, usage requirements propagated
   too. Same code! No changes needed.
   Usage requirements change from one version to another? Again, no
   problems.

So I choose to add CMakeLists.txt almost in all cases when new package 
needed. Exceptions are big libraries with a lot of components such as Qt 
or Boost, it's unmaintainable approach, inevitable evil :(


Ruslo

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Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Ruslan Baratov via CMake]

On 16-Aug-16 17:04, Florent Castelli wrote:


On 16 Aug 2016, at 15:29, Ruslan Baratov > wrote:


On 16-Aug-16 13:52, Florent Castelli wrote:
For example, Boost is used by 5 platforms: Windows, OSX, Linux, 
Android and iOS.

Each platform has a different CPU target (or many 32/64bit, x86/ARM).
Each platform has many compilers.
Some platforms have instrumentation options (Debug / Release, ASan, 
MSan…) and really need

to be compiled properly, otherwise you’ll end up with false positives.
The matrix of builds is REALLY hard to track. Each time we update 
Boost, we had to update

a lot of things.

Not a problem for Hunter.

Linux, OSX, Windows, iOS 9.3, iOS 8.2, Android, GCC, Clang, ASan, 
LeakSan, ThreadSan, Static Analyzer,  libstdc++, libc++, MinGW, 
Visual Studio 2008-2015:

* https://travis-ci.org/ingenue/hunter/builds/140317830
* https://ci.appveyor.com/project/ingenue/hunter/build/1.0.665

This list is not even full, I guess I can add more toolchains in 
future (GCC variations and C++ standards).


To test all matrix I need to push one commit to pkg.boost branch, to 
upload binaries to server I need to push one commit to upload.boost 
branch (upload ALL toolchains at one shot). To reuse all updates 
users just need to set new URL/SHA1 of HunterGate module: 
https://github.com/ruslo/hunter/releases


Overall, building boost takes 10s on our developers’ machines. The 
sources aren’t changed often,

so the cost is pretty low.
What kind of hardware do they have? And what libraries you mean? It 
takes about 20 seconds on my Linux machine just to unpack 80 MB of 
Boost release archive. It's even worse on Windows, it takes several 
minutes for some strange reason even on SSD + Core i7. Using binaries 
in such cases is a huge time saver because there is no need to 
compile anything and there is no a lot of junk that they put into 
release archive (if you remove docs and tests 80 MB became 15 MB).


I consider the time to download Boost isn’t part of the build.
I'm not counting that. It takes 20 seconds just to unpack archive that 
already downloaded. Anyway I'm just wondering what is possible to do 
with Boost for 10 seconds. Install header-only libraries? Build 1-2 
libraries? All of them? :)


The Boost source download is cached outside of the build directory in 
a unique folder.

So it’s effectively only done once for all platforms and then reused.
This is true for local machines and for custom build servers like your 
personal Jenkins. For Travis/AppVeyor you have to create root folder 
with 3rd parties from scratch for each build (at least for free public 
accounts).




You’ll also have symbols and the sources available for debugging 
properly, and they’re

not always available with a binary distribution.
Just to clarify: with Hunter you're creating binaries from sources, so 
everything you install with `cmake --build _builds --target install` (or 
`./b2 install` for Boost) is available.





Of course building from source is not an option for such monsters 
like Qt or OpenCV. Ready-to-use binaries is something critical for 
real life applications. There is no way to test everything on 
Travis/AppVeyor without this feature.


Well, you don’t have to use Travis or AppVeyor.
It's the most powerful and easy to setup services I know. If you know 
any better solutions please share.



Spotify isn’t at the same scale as most
projects hosted there and we have different requirements and resources.
Admittedly, Spotify doesn’t use Qt anymore, so this isn’t a problem 
for us.
It's not about Qt, it's about expandability. Use 20 of smaller libraries 
and you will have quite the same issues.




Note that by integrating everything in the same project, you also have 
proper dependencies
and you will only build what you need. You may save some time by doing 
that.

And caching is important, when done in the right way!
With Hunter you're installing only what you need too, it does respect 
options like FOO_WITH_OPENSSL or FOO_WITH_QT, it download only binaries 
for toolchain you're currently working on, etc.


Don't want to make a discussion too broad. You said that it's hard to 
manage binaries for a lot of configuration, I'm saying that it's 
possible and is very handy.


Ruslo
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Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Ruslan Baratov via CMake]

On 16-Aug-16 13:52, Florent Castelli wrote:

For example, Boost is used by 5 platforms: Windows, OSX, Linux, Android and iOS.
Each platform has a different CPU target (or many 32/64bit, x86/ARM).
Each platform has many compilers.
Some platforms have instrumentation options (Debug / Release, ASan, MSan…) and 
really need
to be compiled properly, otherwise you’ll end up with false positives.
The matrix of builds is REALLY hard to track. Each time we update Boost, we had 
to update
a lot of things.

Not a problem for Hunter.

Linux, OSX, Windows, iOS 9.3, iOS 8.2, Android, GCC, Clang, ASan, 
LeakSan, ThreadSan, Static Analyzer,  libstdc++, libc++, MinGW, Visual 
Studio 2008-2015:

* https://travis-ci.org/ingenue/hunter/builds/140317830
* https://ci.appveyor.com/project/ingenue/hunter/build/1.0.665

This list is not even full, I guess I can add more toolchains in future 
(GCC variations and C++ standards).


To test all matrix I need to push one commit to pkg.boost branch, to 
upload binaries to server I need to push one commit to upload.boost 
branch (upload ALL toolchains at one shot). To reuse all updates users 
just need to set new URL/SHA1 of HunterGate module: 
https://github.com/ruslo/hunter/releases



Overall, building boost takes 10s on our developers’ machines. The sources 
aren’t changed often,
so the cost is pretty low.
What kind of hardware do they have? And what libraries you mean? It 
takes about 20 seconds on my Linux machine just to unpack 80 MB of Boost 
release archive. It's even worse on Windows, it takes several minutes 
for some strange reason even on SSD + Core i7. Using binaries in such 
cases is a huge time saver because there is no need to compile anything 
and there is no a lot of junk that they put into release archive (if you 
remove docs and tests 80 MB became 15 MB).


Of course building from source is not an option for such monsters like 
Qt or OpenCV. Ready-to-use binaries is something critical for real life 
applications. There is no way to test everything on Travis/AppVeyor 
without this feature.


Ruslo
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Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Elizabeth A. Fischer]

CMake builds for existing libraries are certainly an interesting and useful
thing, and deserve to be posted in a GitHub repo somewhere.  They should
also serve as the basis of a campaign to get the library authors to
incorporate the CMake build directly in their repos.

But any approach that requires every build to be ported to CMake will be
difficult and labor-prone to scale.  Writing a meta-build recipe is usually
much easier.

Spack handles the combinatorial dependencies you mention in a
sophisticated, graceful way that most meta-builders do not.  Its only
problem is it does not (yet) run on Windows.  There's no fundamental reason
why not; we just need someone to get involved and start trying it on
Windows.

-- Elizabeth


On Tue, Aug 16, 2016 at 6:52 AM, Florent Castelli <
florent.caste...@gmail.com> wrote:

> At Spotify, we use CMake a lot for our large C++ library shared by all the
> clients.
> After trying to build libraries for each platform and variant, we
> basically gave up and we now
> use a super-build approach.
>
> For example, Boost is used by 5 platforms: Windows, OSX, Linux, Android
> and iOS.
> Each platform has a different CPU target (or many 32/64bit, x86/ARM).
> Each platform has many compilers.
> Some platforms have instrumentation options (Debug / Release, ASan, MSan…)
> and really need
> to be compiled properly, otherwise you’ll end up with false positives.
> The matrix of builds is REALLY hard to track. Each time we update Boost,
> we had to update
> a lot of things.
> I tried using ExternalProject and use b2 (build tool from Boost) to build
> it and instead of having
> lots of build jobs with a mirror of the flags, you end up mirroring the
> flags in your CMake files
> instead, which is still not good enough.
>
> In the end, I looked at how Boost is actually built. And for most
> libraries, it’s plain simple.
> A static library with a few files, some define, sometimes a platform
> specific source file.
> What if instead of having an external build tool, I built it from CMake
> instead?
> It would propagate all the build flags, target, instrumentation and
> compiler information from the main
> build to it and just work.
> I tried it and it worked in no time! We replaced our Boost 1.59 binary
> distribution with the source
> distribution and it’s much easier. When people build our library for a
> different target, they don’t have
> to download new binaries, they just reuse the same sources.
> Later on, we found a bug in Boost 1.59 (fixed in later versions) and
> patched it. We updated our source
> bundle and everything was smooth.
> Much later on, we wanted to use 1.61. We just updated the source bundle
> again, the list of source
> files or compilation flags for the libraries we use didn’t change. It was
> again effortless.
>
> Overall, building boost takes 10s on our developers’ machines. The sources
> aren’t changed often,
> so the cost is pretty low. It needs attention when we upgrade it, but
> that’s quite rare.
>
> We try now to use the same approach for other libraries when we add them.
> Some of them are
> already using CMake and it’s somewhat easier, but since most people still
> target version 2.8 (or 2.6...),
> we find it better to rewrite the build scripts ourselves and use modern
> features (as in, everything is
> a target that propagates requirements, we don’t propagate variables).
> It makes it also much easier to build a library for another platform that
> wasn’t targeted by the original
> project.
>
> If people are interested, I could share the CMakeLists.txt file we use for
> Boost. It doesn’t build all
> the libraries (some are hard like Context) and uses some internal macros,
> but it should be plain
> simple to tweak for your use.
>
> /Florent
>
> > On 12 Aug 2016, at 21:59, Robert Dailey 
> wrote:
> >
> > Hello,
> >
> > There is an internal C++ product at the company I work for which I
> > have written a series of CMake scripts for. This project actually has
> > dependencies on several open source libraries, such as boost,
> > freetype, openssl, etc.
> >
> > Right now what we do is build each of these third party libraries *by
> > hand*, once for every platform we support (Windows, Linux x86, Android
> > NDK). Then we stuff the includes (headers) and libraries
> > (static/shared) in a submodule and the primary code base's CMake
> > scripts pull them in as interface targets.
> >
> > This works well and is light-weight but is a pain when upgrading or
> > changing libraries. It's a pain because if I want to upgrade boost, I
> > have to build it up to 6 times (once for each platform and once for
> > each configuration).
> >
> > I've been thinking of a different approach for a while. I've done some
> > toying around with the "Super Build" concept, where I have a separate
> > CMake project that does nothing but use the ExternalProject module to
> > build libraries in real time along with our project. So the order of
> > operations would be as follows (for our automat

Re: [CMake] [cmake-developers] Need ideas/opinions on third party library management

[Benjamin Ballet via CMake]

Very interesting discussion, we have the same issues here.

Florent Castelli, how many third parties libraries do you use ? I think a
super build can be a very good solution but I'm wondering how much third
party code you have to build. Here we use OpenCV, with, boost, and poco,
and other things... So it may be too long.

I was personnaly considering having an hybrid solution : include small
libraries (like jsoncpp) and pre-build the other for each platforms.


2016-08-16 12:52 GMT+02:00 Florent Castelli :

> At Spotify, we use CMake a lot for our large C++ library shared by all the
> clients.
> After trying to build libraries for each platform and variant, we
> basically gave up and we now
> use a super-build approach.
>
> For example, Boost is used by 5 platforms: Windows, OSX, Linux, Android
> and iOS.
> Each platform has a different CPU target (or many 32/64bit, x86/ARM).
> Each platform has many compilers.
> Some platforms have instrumentation options (Debug / Release, ASan, MSan…)
> and really need
> to be compiled properly, otherwise you’ll end up with false positives.
> The matrix of builds is REALLY hard to track. Each time we update Boost,
> we had to update
> a lot of things.
> I tried using ExternalProject and use b2 (build tool from Boost) to build
> it and instead of having
> lots of build jobs with a mirror of the flags, you end up mirroring the
> flags in your CMake files
> instead, which is still not good enough.
>
> In the end, I looked at how Boost is actually built. And for most
> libraries, it’s plain simple.
> A static library with a few files, some define, sometimes a platform
> specific source file.
> What if instead of having an external build tool, I built it from CMake
> instead?
> It would propagate all the build flags, target, instrumentation and
> compiler information from the main
> build to it and just work.
> I tried it and it worked in no time! We replaced our Boost 1.59 binary
> distribution with the source
> distribution and it’s much easier. When people build our library for a
> different target, they don’t have
> to download new binaries, they just reuse the same sources.
> Later on, we found a bug in Boost 1.59 (fixed in later versions) and
> patched it. We updated our source
> bundle and everything was smooth.
> Much later on, we wanted to use 1.61. We just updated the source bundle
> again, the list of source
> files or compilation flags for the libraries we use didn’t change. It was
> again effortless.
>
> Overall, building boost takes 10s on our developers’ machines. The sources
> aren’t changed often,
> so the cost is pretty low. It needs attention when we upgrade it, but
> that’s quite rare.
>
> We try now to use the same approach for other libraries when we add them.
> Some of them are
> already using CMake and it’s somewhat easier, but since most people still
> target version 2.8 (or 2.6...),
> we find it better to rewrite the build scripts ourselves and use modern
> features (as in, everything is
> a target that propagates requirements, we don’t propagate variables).
> It makes it also much easier to build a library for another platform that
> wasn’t targeted by the original
> project.
>
> If people are interested, I could share the CMakeLists.txt file we use for
> Boost. It doesn’t build all
> the libraries (some are hard like Context) and uses some internal macros,
> but it should be plain
> simple to tweak for your use.
>
> /Florent
>
> > On 12 Aug 2016, at 21:59, Robert Dailey 
> wrote:
> >
> > Hello,
> >
> > There is an internal C++ product at the company I work for which I
> > have written a series of CMake scripts for. This project actually has
> > dependencies on several open source libraries, such as boost,
> > freetype, openssl, etc.
> >
> > Right now what we do is build each of these third party libraries *by
> > hand*, once for every platform we support (Windows, Linux x86, Android
> > NDK). Then we stuff the includes (headers) and libraries
> > (static/shared) in a submodule and the primary code base's CMake
> > scripts pull them in as interface targets.
> >
> > This works well and is light-weight but is a pain when upgrading or
> > changing libraries. It's a pain because if I want to upgrade boost, I
> > have to build it up to 6 times (once for each platform and once for
> > each configuration).
> >
> > I've been thinking of a different approach for a while. I've done some
> > toying around with the "Super Build" concept, where I have a separate
> > CMake project that does nothing but use the ExternalProject module to
> > build libraries in real time along with our project. So the order of
> > operations would be as follows (for our automated build server):
> >
> > 1. Clone our "Third Party" repository
> > 2. Use CMake to generate & build the "Super Build" project (this
> > builds boost, openssl, freetype, etc for the current platform).
> > 3. Clone the main code base's repository
> > 4. Use CMake to generate & build, using find_package() to ref

Re: [CMake] Private dependencies of static libraries exported as targets

[Nicholas Braden]

Yes, the behavior is documented in several places, the most prominent
being here:
https://cmake.org/cmake/help/latest/manual/cmake-buildsystem.7.html#transitive-usage-requirements


On Mon, Aug 15, 2016 at 9:22 PM, Ivan Shapovalov  wrote:
> On 2016-08-15 at 21:46 -0400, Guillaume Dumont wrote:
>> As far as I know the PRIVATE
>> keyword
>> should have no effect on transitive linking when foo is static and we
>> call:
>>
>> target_link_libraries(foo PRIVATE bar)
>>
>> Hope this helps.
>
> Wow. I did not know that. Should've tested on sample project.
> It does not solve include path bloat though, but that's a minor issue.
>
> One question remains... is this behavior documented somewhere?
>
> Anyway, huge thanks,
> --
> Ivan Shapovalov / intelfx /
> --
>
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information on each offering, please visit:

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