[PATCH] D123420: [demangler] Rust demangler buffer reuse

[Tomasz Miąsko via Phabricator via llvm-commits]

tmiasko added a comment.

The API thus far was intended to match that of `__cxa_demangle`, where the caller retains the ownership of the provided buffer when demangling fails. This is no longer the case in the new implementation. I would rather avoid divering from `__cxa_demangle` in such a subtle way.

The Itanium demangler gets away with the direct use of the buffer because it separates fallible parsing from infallible printing.

> the length of the incoming buffer will have come from a previous call, which was the length of the demangled string

I think this is a bug in the implementation. The *N should have been updated to reflect allocated memory size. From Demangler API in Itanium C++ ABI:

> In either case, the new buffer size will be stored in *n.


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  https://reviews.llvm.org/D123420/new/

https://reviews.llvm.org/D123420