https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123989
Bug ID: 123989
Summary: Postfix-expression should be sequenced before each
expression in the expression-list
Product: gcc
Version: 15.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: drippy_carnation182 at simplelogin dot com
Target Milestone: ---
Please see
https://stackoverflow.com/questions/79882580/lambda-argument-that-steals-unique-ptr-used-to-do-the-call/79882716?noredirect=1#comment140971274_79882716
This program
```c++
#include <iostream>
#include <memory>
struct A {
A() { std::cout << "A::A(), this: " << this << std::endl; }
void call(auto lambda) const {
std::cout << "A::call() this: " << this << std::endl;
lambda();
}
};
int main() {
auto p{std::make_unique<A>()};
p->call([p2 = std::move(p)] { std::cout << "From lambda" << std::endl; });
return 0;
}
```
Prints out
```
A::A(), this: 0x53aa2b0
A::call() this: 0x53aa2b0
>From lambda
```
while in this changed form using deducing this
```
#include <iostream>
#include <memory>
struct A {
A() { std::cout << "A::A(), this: " << this << std::endl; }
void call(this const auto& self, auto lambda) {
std::cout << "A::call() this: " << &self << std::endl;
lambda();
}
};
int main() {
auto p{std::make_unique<A>()};
p->call([p2 = std::move(p)] { std::cout << "From lambda" << std::endl; });
return 0;
}
```
it prints (see https://godbolt.org/z/qxjnf5KGq)
```
A::A(), this: 0x3fe662b0
A::call() this: 0
>From lambda
```
It should not print `A::call() this: 0` by
https://timsong-cpp.github.io/cppwp/n4659/expr.call#5
> The postfix-expression is sequenced before each expression in the
> expression-list and any default argument.
