[PATCH] D103750: [analyzer][WIP] Handle std::make_unique for SmartPtrModeling

[Artem Dergachev via Phabricator via cfe-commits]

NoQ added a comment.

In D103750#2803516 <https://reviews.llvm.org/D103750#2803516>, @RedDocMD wrote:

> In D103750#2803499 <https://reviews.llvm.org/D103750#2803499>, @NoQ wrote:
>
>> Ugh, this entire `checkBind` hack was so unexpected that I didn't even recognize `evalCall`. What prevents you from doing everything in `evalCall`? No state traits, no nothing, just directly take the this-region and attach the value to it?
>
> Because in `evalCall`, I don't have access to the `ThisRegion`.

You do have access to it. That's how C++ works: the call constructs the value directly into the target this-region. In code

  auto a = std::make_unique<int>(100)

it is known even before `std::make_unique` is invoked (i.e., even in `checkPreCall`) that the this-region for the call is going to be `a`. Because it's up to the call to invoke the constructor of the external object, and you can't invoke a constructor if you don't have a `this` to pass into it. //You cannot ever have an object and not have `this`.
//
Even if it wasn't for RVO, you would have known the temporary region in which the smart pointer would originally reside.

This was the whole point of the CFG work described in https://www.youtube.com/watch?v=4n3l-ZcDJNY

You're looking in the wrong place though, as `std::make_unique` returns the structure by value (aka prvalue), so the value of the expression, even if available before the call, was never going to be `this` (which would have been the corresponding glvalue). What you're looking for is `CallEvent::getReturnValueUnderConstruction()`.


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