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authorRafael Espindola <rafael.espindola@gmail.com>2013-09-03 21:05:13 +0000
committerRafael Espindola <rafael.espindola@gmail.com>2013-09-03 21:05:13 +0000
commitee6aa0c62e8b9bc7fc63efe0abf78f0918d12808 (patch)
treede2a483004e571695b18c2f8605fe553c7398cd4 /clang/lib/CodeGen/CodeGenModule.cpp
parentf58070baed3a05c90e5d5fb969c612472eea4e3d (diff)
downloadbcm5719-llvm-ee6aa0c62e8b9bc7fc63efe0abf78f0918d12808.tar.gz
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Don't emit an available_externally vtable pointing to linkonce_odr funcs.
This fixes pr13124. From the discussion at http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-June/022606.html we know that we cannot make funcions in a weak_odr vtable also weak_odr. They should remain linkonce_odr. The side effect is that we cannot emit a available_externally vtable unless we also emit a copy of the function. This also has an issue: If codegen is going to output a function, sema has to mark it used. Given llvm.org/pr9114, it looks like sema cannot be more aggressive at marking functions used because of vtables. This leaves us with a few unpleasant options: * Marking functions in vtables used if possible. This sounds a bit sloppy, so we should avoid it. * Producing available_externally vtables only when all the functions in it are already used or weak_odr. This would cover cases like -------------------- struct foo { virtual ~foo(); }; struct bar : public foo { virtual void zed(); }; void f() { foo *x(new bar); delete x; } void g(bar *x) { x->~bar(); // force the destructor to be used } -------------------------- and ---------------------------------- template<typename T> struct bar { virtual ~bar(); }; template<typename T> bar<T>::~bar() { } // make the destructor weak_odr instead of linkonce_odr extern template class bar<int>; void f() { bar<int> *x(new bar<int>); delete x; } ---------------------------- These look like corner cases, so it is unclear if it is worth it. * And finally: Just nuke this optimization. That is what this patch implements. llvm-svn: 189852
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