> On Apr 26, 2025, at 10:22, Federico Kircheis via Std-Discussion <std-discussion_at_[hidden]> wrote:
>
> On 26/04/2025 4:05 pm, mauro russo wrote:
>>
>
>> > * if different function can have the same address, the class if
>> > broken, (the lifetime of the previous object did not end correctly)
>> This should be something never happening. It cannot make sense
>> to have different functions at the same address.
>
> IMHO it makes sense that
>
> void foo(){}
> void bar(){}
>
> can have the same address, similarly to how identical string literals can have the same address; I was not sure if such optimization was allowed.

I think it's forbidden by expr.eq p3.2-3.3 (https://eel.is/c++draft/expr.eq#3.2). Two function pointers compare equal if and only if they "point to the same function". I think it's clear that foo() and bar() are not "the same function", even if they perform the same behavior.

String literals have an explicit exemption from this rule per intro.object p9 (https://eel.is/c++draft/intro.object#9).

Somewhat related, clang does a "controversial" optimization where, if a function would unconditionally cause UB if called, the compiler emits a label for it but no code, not even a return instruction. As such, the next function compiled can end up at the same address. See https://godbolt.org/z/775s6e4vv for an example. This does seem like a clear violation of expr.eq p3, but it's been unfixed for a long time.

So if the situation for lambdas is different, it must be something specific to them.