CWG2597 Replaceable allocation and deallocation functions in the global module

[jensmaurer]

Subclause 10.1 [module.unit paragraph 7] implicitly attaches the replaceable global allocation or deallocation functions to the global module. Now that extern "C++" can be used to introduce declarations in the global module, even when in the purview of a named module, the provision seems superfluous.

https://cplusplus.github.io/CWG/issues/2597.html

Example:

module M;
void * operator new(std::size_t);  // before: well-formed; after: ill-formed because attachment conflict with the predeclared version
extern "C++" void * operator new(std::size_t);   // well-formed before and after

This is a user-visible design change, imposing a small ergonomic cost for a rare case in exchange for the removal of a special case, and thus should have EWG approval.

[ChuanqiXu9]

Should we change the suggested wording into the following?

and should be attached to the global module, otherwise the program is ill-formed.

Otherwise, I might recognize the example is well-formed personally.

module M;
void * operator new(std::size_t);

[jensmaurer]

Note that this github paper tracker is for administration only, not for technical discussion.

(In your example, your declaration of "operator new" is attached to M, which conflicts with the attachment of the predeclared "operator new". And that's ill-formed.)

[erichkeane]

This was discussed during the July 7th, 2022 EWG Telecon. The following Poll was taken:

EWG agrees with the resolution of CWG2597 as proposed.

SF	F	N	A	SA
4	6	0	0	0

Result: Consensus

Consensus was strong, and discussion didn't result in any one having concerns, so forwarding without Electronic Polling was ruled acceptable.

[jensmaurer]

CWG telecon 2022-07-15: Approved.

[tkoeppe]

This has been applied.