[PATCH] D113676: WIP: [clang][lex] Fix search path usage remark with modules

Jan Svoboda via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Fri Nov 12 03:44:06 PST 2021

jansvoboda11 added a comment.

Thanks for the feedback, I'll try to clean this up a bit.

Comment at: clang/lib/Lex/HeaderSearch.cpp:94
+      // Module map parsing initiated by header search.
+      if (HS.CurrentSearchPathIdx != ~0U)
+        HS.ModuleToSearchDirIdx[M] = HS.CurrentSearchPathIdx;
ahoppen wrote:
> When would the `moduleMapModuleCreated` be called while `CurrentSearchPathIdx == ~0U`? Could this be an `assert` instead?
This happens whenever any of the `ModuleMap` member functions that create new `Module` instances are called outside of `HeaderSearch`.

The `MMCallback` callback is basically "global" (present for the whole lifetime of `ModuleMap`), so that we don't have to repeatedly register/deregister it in `HeaderSearch::lookupModule`.

Comment at: clang/lib/Lex/HeaderSearch.cpp:264
+  if (Module || !AllowSearch || !HSOpts->ImplicitModuleMaps) {
+    noteModuleLookupUsage(Module, ImportLoc);
     return Module;
ahoppen wrote:
> Just a thought: Could we move `noteModuleLookupUsage` into `findModule`? IIUC that would guarantee that we’re catching all cases and we wouldn’t need to call `noteModuleLookupUsage ` from both overloads of `lookupModule`.
That would clean up `HeaderSearch` nicely. I'll look into creating new `HeaderSearch::findModule` function that would wrap `ModuleMap::findModule` and note usage.

Comment at: clang/lib/Lex/ModuleMap.cpp:851
       new Module("<private>", Loc, Parent, /*IsFramework*/ false,
                  /*IsExplicit*/ true, NumCreatedModules++);
   Result->Kind = Module::PrivateModuleFragment;
ahoppen wrote:
> Maybe a stupid question but why don’t we need to call the callback e.g. here (or on the other `new Module`) calls in this file?
This is related to C++20 modules, so it wasn't necessary for the test case I had in mind.

But I agree we should handle this as well. I think more robust solution would be to add factory function to `ModuleMap` through which all `Module` instances get created, and invoke the callback there.

  rG LLVM Github Monorepo



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