Discussion
Fucked C++ question:
I have a struct B, defined by me. I had the code
auto &b = bees.emplace_back(); //vector
b.value = 3;
A change *ELSEWHERE IN THE CODE* caused this to suddenly start failing with
"auto cannot be inferred"
changed the line to
B &b = bees.emplace_back();
The error became ("bees" underlined):
"initial value of reference to non-const must be an lvalue" (??)
Replaced the whole thing with
B b;
b.value = e;
bees.push_back(b);
The compiler allows this.
C++17.
wha ??? ?? ?????
@mcc Not at all sure but it sounds a bit like you clobbered the name resolution of `bees`, similar to what happens when you write `get<string>(myVariant)` in a member function (intending for it to be resolved to `std::get` via `using namespace std`) and then later add a member function called `get` to that same class
Or the incomprehensible errors you get if Windows' `near`/`far` macros clobber anything unexpected
@AminiAllight no, this is a typo in my post. The class is not named B and the vector is not named bees. I have edited the post to be more correct.
@mcc a change to B making it no longer MoveInsertable / EmplaceConstructible ?
@porglezomp Very interesting.
Do you believe my push_back implementation will have move semantics, or do you believe I have just created a copy?
@mcc I’m not confident about when copies happen in C++, I’m so frustrated that there is very little way to tell the difference, since moves silently become copies if anything is slightly odd.
My suggestion is really just from long ago experience with the types of spooky action at a distance, and looking at the cppreference documentation of emplace_back to see what requirements it imposed on the types.
@mcc typo in your replacement that might be confusing people: I assume you mean `bees.push_back(b);`