[llvm] r337366 - [CMake] Export the LLVM_LINK_LLVM_DYLIB setting

[Philip Pfaffe via llvm-commits]

I haven't tried it yet, but wouldn't that give me duplicate symbols/cl
options when linking against libLLVM _and_ a clang library linked
statically?

On Tue, Jul 24, 2018 at 1:33 PM Pavel Labath <labath at google.com> wrote:

> I don't think I know all the implications of this, but would it be
> possible to export LLVM_**BUILD**_LLVM_DYLIB instead of this option?
> That way, the external projects will still be able to determine
> whether the library exists at all, but they will have the option to
> independently control whether they want to link to it or not?
> On Tue, 24 Jul 2018 at 11:55, Philip Pfaffe <philip.pfaffe at gmail.com>
> wrote:
> >
> > I can reproduce the not-linking-with-dylib bit, but it doesn't fail
> during linking for me. That's why I missed this in testing. Sorry!
> >
> > Is this serious enough to revert to unbreak you?
> >
> > Alternatively there's two quick fixes for this:
> > - Make LLVM_LINK_LLVM_DYLIB an option() in LLVMConfig.cmake. Then it'll
> show up in the GUI and respects configurations.
> > - Wrap the set() in an if().
> >
> > I'd prefer going the option() route. Adding a CLANG_LINK_LLVM_DYLIB
> additionally is worth considering, I'd prefer doing that as a seperate
> change though.
> >
> > Cheers,
> > Philip
> >
> > On Tue, Jul 24, 2018 at 1:30 AM Justin Bogner <mail at justinbogner.com>
> wrote:
> >>
> >> Philip Pfaffe via llvm-commits <llvm-commits at lists.llvm.org> writes:
> >> > Author: pfaffe
> >> > Date: Wed Jul 18 01:53:31 2018
> >> > New Revision: 337366
> >> >
> >> > URL: http://llvm.org/viewvc/llvm-project?rev=337366&view=rev
> >> > Log:
> >> > [CMake] Export the LLVM_LINK_LLVM_DYLIB setting
> >> >
> >> > Summary:
> >> > When building out-of-tree tools, there are several macros available to
> >> > automate linking against llvm. An examples is `add_llvm_executable`,
> or
> >> > the clang variant of this.
> >> >
> >> > These macros use the LLVM_LINK_LLVM_DYLIB option to decide whether to
> >> > link against libraries defined by setting LLVM_LINK_COMPONENTS or to
> >> > link against libLLVM instead. Currently this is problematic in
> >> > out-of-tree targets, because they cannot identify whether this option
> is
> >> > required or even available. If the option was enabled in LLVM's own
> >> > build, the clang libraries are built against libLLVM, so a client
> >> > linking against those must link against it too. On the other hand the
> >> > client can't just always link against it, because it might not be
> >> > available.
> >>
> >> I'm not sure I understand the problem this is solving, but it breaks the
> >> case where an out-of-tree target tries to link the dylib when the
> >> in-tree build does not. Specifically, if I build llvm with
> >> LLVM_LINK_LLVM_DYLIB=Off (but LLVM_BUILD_LLVM_DYLIB=On), and then I try
> >> to build clang against this with LLVM_LINK_LLVM_DYLIB=On, clang's
> >> setting of the variable seems to be ignored and I get link errors as it
> >> looks for static libraries.
> >>
> >> Can this be made to respect externally setting the variable? Maybe it
> >> should only show up if set, for example? Alternatively, do external
> >> projects need to implement their own version of the variable, like a
> >> CLANG_LINK_LLVM_DYLIB?
> >>
> >> > This is related to D44391, but that change assumed the client knew
> >> > whether they wanted the dylib or not.
> >> >
> >> > Reviewers: mgorny, beanz, labath
> >> >
> >> > Reviewed By: mgorny
> >> >
> >> > Subscribers: bollu, llvm-commits
> >> >
> >> > Differential Revision: https://reviews.llvm.org/D49193
> >> >
> >> > Modified:
> >> >     llvm/trunk/cmake/modules/LLVMConfig.cmake.in
> >> >
> >> > Modified: llvm/trunk/cmake/modules/LLVMConfig.cmake.in
> >> > URL:
> >> >
> http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/modules/LLVMConfig.cmake.in?rev=337366&r1=337365&r2=337366&view=diff
> >> >
> ==============================================================================
> >> >
> >> > --- llvm/trunk/cmake/modules/LLVMConfig.cmake.in (original)
> >> > +++ llvm/trunk/cmake/modules/LLVMConfig.cmake.in Wed Jul 18 01:53:31
> 2018
> >> > @@ -13,6 +13,8 @@ set(LLVM_COMMON_DEPENDS @LLVM_COMMON_DEP
> >> >
> >> >  set(LLVM_AVAILABLE_LIBS @LLVM_AVAILABLE_LIBS@)
> >> >
> >> > +set(LLVM_LINK_LLVM_DYLIB @LLVM_LINK_LLVM_DYLIB@)
> >> > +
> >> >  set(LLVM_DYLIB_COMPONENTS @LLVM_DYLIB_COMPONENTS@)
> >> >
> >> >  set(LLVM_ALL_TARGETS @LLVM_ALL_TARGETS@)
> >> >
> >> >
> >> > _______________________________________________
> >> > llvm-commits mailing list
> >> > llvm-commits at lists.llvm.org
> >> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180724/c58c1bee/attachment.html>