We've been seeing (rare) crashes from both
`CPlusPlusLanguage::SymbolNameFitsToLanguage` and
`ObjCLanguage::SymbolNameFitsToLanguage` when we try to read contents of
the `ConstString`s of the `Mangled` parameter. I'm not entirely sure how
that can happen (current theory is corrupted stack somehow which
overwrites `ConstString::m_string` to an invalid pointer) but I'm not
able to confirm that.
One thing these crashes had in common is that they operate on the
`Mangled` object we copied into `SymbolNameFitsToLanguage` by value.
While I can't see off the top why that would cause it to contain
unintiailized/corrupt `ConstString`s, the class is sufficiently large
enough to probably pass it by `const &` anyway. This is what this patch
does.
rdar://164519648
0f4dc93608