Hi all, n00b here. I'm trying to compile the examples used by the book Beginning C++20 (by Horton and Van Weert) but the "import <iostream>;" part gives me errors. I've done some searching, and found out that I need a non-default version of gcc (10 or 11) with support for Modules. I've installed gcc-11 as indicated on the Wiki page (https://gcc.gnu.org/wiki/cxx-modules) and the example code there works fine. Now when I use g++ -fmodules-ts Ex1_01.cpp I get the following error: In module imported at Ex1_01.cpp:3:1: /usr/local/include/c++/11.0.0/iostream: error: failed to read compiled module: No such file or directory /usr/local/include/c++/11.0.0/iostream: note: compiled module file is ‘gcm.cache/./usr/local/include/c++/11.0.0/iostream.gcm’ /usr/local/include/c++/11.0.0/iostream: note: imports must be built before being imported /usr/local/include/c++/11.0.0/iostream: fatal error: returning to the gate for a mechanical issue compilation terminated. THIS IS AN IN-DEVELOPMENT COMPILER, it ate something that didn't agree with it See <https://gcc.gnu.org/wiki/cxx-modules#Bugs>, WHICH IS NOT THE USUAL REPORTING MECHANISM! After some more searching I've found this website: https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Modules.html which says the following: The Standard Library is not provided as importable header units. If you want to import such units, you must explicitly build them first. So, my problem/question is: How do I do this? The only thing I can find is that the -fmodule-header flag should be used, but not howto build a Header unit. Patrick
