[PATCH] D136953: [C++20] Diagnose invalid and reserved module names

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/lib/Sema/SemaModule.cpp:282
+  StringRef FirstComponentName = Path[0].first->getName();
+  if (!getSourceManager().isInSystemHeader(Path[0].second) &&
+      (FirstComponentName == "std" ||
----------------
ChuanqiXu wrote:
> cor3ntin wrote:
> > ChuanqiXu wrote:
> > > std modules should be irreverent with system headers; The intuition of the wording should be that the users can't declare modules like `std` or `std.compat` to avoid possible conflicting. The approach I imaged may be add a new compilation flags (call it `-fstd-modules`) now. And if the compiler found a `std` module declaration without `-fstd-modules`, emit an error.  
> > > 
> > > For now, I think we can skip the check for `-fstd-modules` and add it back when we starts to support std modules actually.
> > The idea is that standard modules are built from system directories... it seems a better heuristic than adding a flag for the purpose of 1 diagnostics ( maybe some other system library could in theory export std with no warning, but I'm not super worried about that being a concern in practice)
> > The idea is that standard modules are built from system directories...
> 
> This is not true. For example, if someday libc++ supports std modules, then we need to build the std modules in our working directory, which is not system directories. And **ideally**, we would distribute and install module file in the system directories. But it is irreverent with the path of the source file.
> then we need to build the std modules in our working directory, which is not system directories.

`-isystem`, pragmas, and linemarkers are all ways around that -- I don't think we need a feature flag for this, unless I'm misunderstanding something.


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  https://reviews.llvm.org/D136953/new/

https://reviews.llvm.org/D136953