https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105985
Bug ID: 105985
Summary: The case of "indirectly" exported by the primary
module interface unit is not accepted
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: xmh970252187 at gmail dot com
Target Milestone: ---
// translation unit C
export module M :C;
// translation unit U
export module M :U;
import :C;
// translation unit T
export module M;
export import :U; // #1
[module.unit] says
> All module partitions of a module that are module interface units shall be
> directly or indirectly exported by the primary module interface unit
> ([module.import]). No diagnostic is required for a violation of these rules.
[module.import] p7 says
> When a module-import-declaration imports a translation unit T, it also
> imports all translation units imported by exported module-import-declarations
> in T; such translation units are said to be exported by T. Additionally, when
> a module-import-declaration in a module unit of some module M imports another
> module unit U of M, it also imports all translation units imported by
> non-exported module-import-declarations in the module unit purview of U.
> These rules can in turn lead to the importation of yet more translation units.
It is clear that "U" is exported by "T" since an exported
module-import-declaration at #1 imports "U" in "T", which is exactly said in
the first part of [module.import] p7.
Since "T" and "U" are both module units of "M", the second part of
[module.import] p7 should apply to the "module-import-declaration" at #1, since
the "non-exported module-import-declaration"("import :C;") appears in U, the
module-import-declaration at #1 should also import "C". So, "C" is arguably
said that it is indirectly exported by "T". All partition module interface
units of M are exported by the primary module interface unit of M. There is no
violation here.
However, If we compile the example through GCC, it reports an error that:
> interface partition is not exported
