[class], [dcl] Some "before" should refer to "happens-before" relationship in these clauses

[xmh0511]

Full name of submitter (unless configured in github; will be published with the issue): Jim X

For example, [class.cdtor] p1 says

For an object with a non-trivial constructor, referring to any non-static member or base class of the object before the constructor begins execution results in undefined behavior.

The wording "before" in this sentence should refer to "happens-before" such that the behavior is defined in the multithread context. This is true for "after". There are many such cases in the clause [class].

In clause [dcl], for example, [dcl.fct.def.coroutine] p14

The lifetime of parameter copies ends immediately after the lifetime of the coroutine promise object ends.

[dcl.init.ref] p2

A reference cannot be changed to refer to another object after initialization.

In addition, we seem to have never defined which evaluations are considered within the lifetime of an object in [basic.life].

[safocl]

It seems to me that this is simply an attempt to replace all the words "before" with the phrase "happens-before", since the latter means precisely the relationship of actions between themselves in the order of execution, and not for use in a condition when describing behavior.

here it is not stipulated that any action is performed "before" (or "after") some other action - here it is said that if it is performed "before" (or "after") some action, then it has certain effects.

[xmh0511]

here it is not stipulated that any action is performed "before" (or "after") some other action - here it is said that if it is performed "before" (or "after") some action, then it has certain effects.

Define the "before" in your meaning.

[eisenwave]

Define the "before" in your meaning.

At least one microsecond earlier ([time]).

[xmh0511]

Define the "before" in your meaning.

At least one microsecond earlier ([time]).

The “before” in clauses [class] and [dcl] sometimes means "happens-before", and sometimes means "precedes in the position", i.e., not all of them means "happens-before".

[safocl]

The “before” in clauses [class] and [dcl] sometimes means "happens-before", and sometimes means "precedes in the position", i.e., not all of them means "happens-before".

For example, [class.cdtor] p1 says

For an object with a non-trivial constructor, referring to any non-static member or base class of the object before the constructor begins execution results in undefined behavior.

How will this sentence work if we substitute "happens before"?
here we are talking specifically about "referring to class subobject", and not about an execution dependency, since a "referring" is not an action (as I think).

in other words, we are talking about the location in the code, and not about the execution of the program (again, as I see from the text of these provisions of the standard).

[xmh0511]

The “before” in clauses [class] and [dcl] sometimes means "happens-before", and sometimes means "precedes in the position", i.e., not all of them means "happens-before".

For example, [class.cdtor] p1 says

For an object with a non-trivial constructor, referring to any non-static member or base class of the object before the constructor begins execution results in undefined behavior.

How will this sentence work if we substitute "happens before"? here we are talking specifically about "referring to class subobject", and not about an execution dependency, since a "referring" is not an action (as I think).

"referring" is produced by an evaluation. See [intro.execution] p7

Evaluation of an expression (or a subexpression) in general includes both value computations (including determining the identity of an object for glvalue evaluation and fetching a value previously assigned to an object for prvalue evaluation) and initiation of side effects.

How will this sentence work if we substitute "happens before"?

For example:

For an object with a non-trivial constructor, referring to any non-static member or base class of the object that does not happen after the constructor begins execution results in undefined behavior.

[safocl]

In my opinion, the example at [class.cdtor#example-1] quite reasonably demonstrates why everything is fine in the discussed wording of the standard.

[xmh0511]

In my opinion, the example at [class.cdtor#example-1] quite reasonably demonstrates why everything is fine in the discussed wording of the standard.

I just need to point out one problem: the comment in the example says

undefined, x is not yet constructed

So, what "x is not yet constructed" exactly means is not well-defined.

[safocl]

I just need to point out one problem: the comment in the example says

undefined, x is not yet constructed

So, what "x is not yet constructed" exactly means is not well-defined.

How, in your understanding, could replacing "before" with "happens before" help here in principle? (Although I don't see any problems at all in the examples provided in the standard.)

[xmh0511]

could replacing "before" with "happens before" help here in principle?

The standard defines what "happens before" means; instead, we don't define what "before" means in this context.

[safocl]

could replacing "before" with "happens before" help here in principle?

The standard defines what "happens before" means; instead, we don't define what "before" means in this context.

[dcl.init.ref] p2

A reference cannot be changed to refer to another object after initialization.

Can you think of even one case where such a contract was violated due to the lack of "synchronizes with" between two execution points? (Is this even possible in your opinion?)
It simply cannot be written syntactically (semantically) correctly.