[cfe-dev] typeinfo visibility for pointer to incomplete type

[Vedant Kumar via cfe-dev]

What version of clang are you using?

I tried referring to the typeid of SomeClass* from two different compilation
units and ended up with just one copy of __ZTSP9SomeClass in my binary. The
symbol is marked as 'linkonce_odr constant' in LLVM IR, which checks out.

$ nm -m t | grep ZTSP9SomeClass       
0000000100001f60 (__TEXT,__const) weak external __ZTSP9SomeClass

best,
vedant

> On Jan 20, 2017, at 5:15 AM, Douwe Gelling via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> 
> Hi all,
> 
> When taking the typeinfo of a pointer to incomplete type, clang++ emits type info for the pointer in the resulting binary, but makes that typeinfo non-external (on osx at least). Is this intended? I'd have expected it to be weak external so that when the type is defined in other compilation units, the typeinfo isn't defined multiple times.
> 
> sample code:
> 
> #include <typeinfo>
> #include <iostream>
> class SomeClass;
> 
> int main()
> {
>   std::cout << typeid(SomeClass*).name() << std::endl;
> }
> 
> when running nm -m on the resulting binary, it contains:
> 
> 0000000000000414 (__TEXT,__const) non-external __ZTSP9SomeClass
> 
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