[Bug c++/114990] Compiler errors in <type_traits> compiling a module-based app

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114990

--- Comment #12 from cqwrteur <unlvsur at live dot com> ---
(In reply to Jason Merrill from comment #10)
> (In reply to cqwrteur from comment #9)
> > (In reply to Jason Merrill from comment #8)
> > > bar.cppm:4:20: error: conflicting declaration of ‘void foo()’ in module ‘bar’
> > >     4 | export inline void foo() noexcept;
> > >       |                    ^~~
> > > In file included from bar.cppm:2:
> > > someheader.hpp:1:13: note: previously declared in global module
> > 
> > That is my problem. This just breaks header only libraries right?
> 
> No, you just need to #include the library header before the "export module"
> line.  Or better yet, use import <header> instead of #include.
> 
> > This is the same.
> > 
> > import std;
> > #include<aheaderonlylibrary> //it uses std features.
> > 
> > This is absolutely the standard bug.
> 
> This is a GCC bug, as described in comment #1.  If you
> 
> import <aheaderonlylibrary>;
> 
> instead, it should work fine.  Naturally, that requires that you first
> 
> g++ -fmodules-ts -c -x c++-system-header aheaderonlylibrary

std is actually just one example. It applies to any library that have the same
dependency issue.