[LLVMdev] Disabling rtti on default build - could it be reverted/re-enabled?

Pekka Jääskeläinen pekka.jaaskelainen at tut.fi
Thu Feb 18 15:42:56 PST 2010

Chris Lattner wrote:
>> Mainly this is about a nuisance to need to ask users of TCE to recompile 
>> LLVM (which might be even installed from a precompiled binary for their
>> distro) to be able to compile TCE.
> I'm dubious that doing that would actually work anyway.  Since LLVM doesn't
> provide a stable API, being able to reuse a previously installed version of
> llvm is not very likely to work.

Yes, we as an external project using LLVM as a library are painfully
familiar with the unstable API by now :)

Anyhow, people might have LLVM (a supported version) installed (compiled
with the default compilation flags or installed from a binary package
of their distro) for other reasons than compiling TCE.

 From now on these users need to recompile LLVM from sources with non-default
flags to make TCE (or other external projects using both LLVM and RTTI) to
be able to link with it. I think this should matter something in comparison to
a 5% disk size reduction which can be still achieved with disabling RTTI
when compiling LLVM for low disk space devices or during LLVM development
that requires frequent recompiles.

As far as I understood, enabling RTTI by default does not break any
clients, but disabling does. So I guess it's a matter how much value
the LLVM project gives to external projects using LLVM as a library.

How much is the compile time speedup BTW, has it been measured?


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