2012/10/9 James Bigler <jamesbig...@gmail.com>:
>
> I spent some time in the debugger to try and understand why CMake is making
> the decisions it is. It comes down to this function which loops over all
> the LinkClosures and calls AddImplicitLinkInfo for all languages that
> *don't* match the language of the target.
>
> //----------------------------------------------------------------------------
> void cmComputeLinkInformation::AddImplicitLinkInfo()
> {
> // The link closure lists all languages whose implicit info is needed.
> cmTarget::LinkClosure const*
> lc=this->Target->GetLinkClosure(this->Config);
> for(std::vector<std::string>::const_iterator li = lc->Languages.begin();
> li != lc->Languages.end(); ++li)
> {
> // Skip those of the linker language. They are implicit.
> if(*li != this->LinkLanguage)
> {
> this->AddImplicitLinkInfo(*li);
> }
> }
> }
>
>
> The LinkClosure is computed and the only language in it is CXX due to the
> CXX-ness of the input sources. I'm not sure what to think about this. I
> told CMake to link the target as if it were a C target, then it decides that
> it needs CXX libraries because it found CXX sources in my library.
>
> If I go through the trouble of specifying that I want to link the library as
> if it were C, why do the source files get to override my property?
>
> It also seems to me that the source file language should only guide the link
> language when the user didn't specify it explicitly.
I agree with you even if it looks like a feature side-effect.
It looks like if you need to
set(CMAKE_CXX_LINKER_PREFERENCE_PROPAGATES 0)
in order to make your current problem disappear (at least on Linux)
I would bet that this "feature" did not include a test with a "single
source" file.
I would also bet that Brad should answer to this:
commit fcab87c9f802965318bee033c2fa3ff27cfbfec7
Author: Brad King <brad.k...@kitware.com>
Date: Thu Jul 30 10:59:37 2009 -0400
Do not always propagate linker language preference
The commit "Consider link dependencies for link language" taught CMake
to propagate linker language preference from languages compiled into
libraries linked by a target. It turns out this should only be done for
some languages, such as C++, because normally the language of the
program entry point (main) should be used.
We introduce variable CMAKE_<LANG>_LINKER_PREFERENCE_PROPAGATES to tell
CMake whether a language should propagate its linker preference across
targets. Currently it is true only for C++.
commit fd633b33cff397b110cc69f82fd522cdf905952a
Author: Brad King <brad.k...@kitware.com>
Date: Thu Jul 30 10:59:25 2009 -0400
Refactor target linker language selection
This factors the decision logic out of cmTarget::ComputeLinkClosure into
dedicated class cmTargetSelectLinker. We replace several local
variables with a single object instance, and organize code into methods.
--
Erk
Le gouvernement représentatif n'est pas la démocratie --
http://www.le-message.org
--
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
Follow this link to subscribe/unsubscribe:
http://www.cmake.org/mailman/listinfo/cmake
