How can I check if a move constructor is being generated implicitly?

Question

I have several classes for which I wish to check whether a default move constructor is being generated. Is there a way to check this (be it a compile-time assertion, or parsing

Answer 1

1. disable inlining (-fno-inline)
2. either
   • make sure a move constructor can be used by the code, or (better)
   • temporarily add a call to std::move(MyStruct) anywhere in the compiled code to meet the odr-used requirement
3. either
   • make sure that MyStruct has at least one parent class or a non-static member (recursively), with a non-trivial move constructor (e.g. an std::string would suffice), or (easier)
   • temporarily add an std::string member to your class
4. compile/link and run the resultant object file through nm -C ... | grep 'MyStruct.*&&'

The result will imply whether the move constructor was generated or not.

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As discussed in the question itself, this method didn't seem to work reliably, but after fixing the two issues that made it unreliable: inlining and triviality of the move constructor, it turned out to be a working method.

Whether the generated move constructor is implicitly or explicitly defaulted plays no role—whether the default is trivial or not is relevant: a trivial move (and copy) constructor will simply perform a byte-wise copy of the object.