[cfe-dev] Disallow rtti

David Chisnall via cfe-dev cfe-dev at lists.llvm.org
Wed Oct 25 01:25:07 PDT 2017

On 24 Oct 2017, at 18:48, Martin J. O'Riordan via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> I have not found the overhead of RTTI to be a significant burden (even for embedded with a 128KB memory size constraint)

With only 128KB of ROM, you’re going to find it hard to fit a C++ runtime library (though if you rip out the demangler you’ll save quite a lot), so even if you compile with RTTI, you won’t be able to use it or throw exceptions.  A stack unwinder plus the C++ personality function can easily add up to more than the ROM on such devices.  It’s possible to fit just enough support for dynamic_cast on such a system, but it’s somewhat awkward to have dynamic_cast working but exceptions not working.


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