C++ PATCH: fix PR 28687
Fri Aug 11 21:29:00 GMT 2006
Gabriel Dos Reis wrote:
> Benjamin Smedberg <email@example.com> writes:
> | Previously the construct dynamic_cast<void*> worked even when RTTI was
> | disabled, and was useful in Mozilla logging code. PR10891 changed this
> | behavior so that dynamic_cast is forbidden unconditionally when -fno-rtti is
> | used.
> That assertion is untrue. The documentation for -fno-rtti is clear
> about the dynamic_cast. If -fno-rtti, you can't meaningfully do
Which one? That it worked previously is a statement of fact, not really
disputable. Mozilla logging code would be a shambles if this were not the case.
That it continues to work is a matter of logic and code examination. The
code in question is in build_headof() in rtti.c: the offset from a pointer
to the most-derived class pointer is contained in the vtable in position -2.
No RTTI symbol lookups are performed during this process.
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