[cfe-dev] Clang 3.5 Release Pre-Pre-Pre-Announcement

[Rafael Espíndola]

> I don't think maintaining import/export annotations in the source code is
> viable in LLVM.
>
> We'd be looking at hundreds of macros like EXPORT_IF_HAVE_CLANG and
> IMPORT_IF_MODULAR_BUILD, EXPORT_IF_NOT_MONOLITHIC_LLVMCLANG attached to
> functions and classes throughout LLVM. Yuck :-(

Well, we can always start with the most conservative case, no? Just a
LLVM_EXPORT that gets added if the symbol is needed in *any*
configuration. That would be better than what we have now for ELF and
would make it possible to get dll builds on windows.

> Excessive exports would prevent optimisations and inlining without any clear
> way to prune them as the code changes. LTO would have to export all these
> functions just in case something might be using them.

That is the current situation on ELF/MachO :-(

> The only way to detect when new exports are needed would be to observe build
> bot breakage and add them incrementally until the bots turn green. Or to
> keep a shared build matching the DLL configuration.
>
> It's really burdensome to have to modify the original *definition* every
> time you want to use a class or function. You'll no longer be able to
> develop and test a local clang branch against upstream LLVM, which will
> discourage people from developing against ToT.
>
> And finally, the risk of breaking the build will be high enough to tip the
> balance in favour of copy-and-pasting the necessary code from LLVM core into
> clang in order to use it. It's not like we don't already have a
> copy-and-paste problem and this would legitimise the practice.
>
> TLDR; We _really_ want to calculate these dependencies at build time with
> LLVMBuild instead of annotating the source.

Is there a convenient way to feed this to link.exe?

Cheers,
Rafael