https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115190
--- Comment #3 from huangqinjin at gmail dot com ---
(In reply to Peter Damianov from comment #2)
> I could only reproduce this on MSYS2's gcc packages. On w64devkit, I
> couldn't reproduce it. Nor with a gcc 15 I built myself.
>
Oh yes, I made another test, but the error message is different.
$ printf 'test test.gcm\r\n' > a.modmap
$ echo 'export module test;' > test.cpp
$ g++ -std=c++20 -fmodules-ts -fmodule-mapper=a.modmap -c test.cpp
test.cpp:1:8: error: unknown Compiled Module Interface: no such module
1 | export module test;
| ^~~~~~
test.cpp:1:8: warning: not writing module 'test' due to errors
