[PATCH] D62112: [ORC] fix use-after-move. NFC

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

In D62112#1511074 <https://reviews.llvm.org/D62112#1511074>, @nickdesaulniers wrote:

> > because is it a string reference? (that might be invalidated by the move), a return by value (that then means it's reference extending, which is best avoided unless really needed),
>
> Do you have links or more info to these problems? I've never heard the term "reference extending" before.


Here's some info on reference lifetime extension: https://abseil.io/tips/107

As for string reference invalidation, I was picturing something like this:

  struct foo { std::string s; const std::string &get_foo() { return s; } }; //struct isn't necessary, but to make it closer to the example
  void func(foo f) {
    const std::string &ref = f.get_foo();
    foo g = std::move(f);
    /* do things with 'ref' here */
  }

but at the last line there, the string inside 'f' has been moved into 'g', so the reference refers to the std::string in 'f' which is now in a valid but unspecified state (could contain the original string data (probably does if it's short enougH), or could point to a zero-length/empty string (if the data was too long and was dynamically allocated, and thus the allocation was moved over to the string in 'g' instead))


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