[PATCH] D110215: [C++2a] [Module] Support extern C/C++ semantics

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:16155
+  if (getLangOpts().CPlusPlusModules) {
+    auto *GlobalModule =
+        PushGlobalModuleFragment(ExternLoc, /*IsImplicit=*/true);
----------------
`Module *` instead of `auto *` (the type is not spelled out in the initialization).


================
Comment at: clang/lib/Sema/SemaModule.cpp:71
   // module-private (though they do not have module linkage).
-  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
-  auto *GlobalModule = Map.createGlobalModuleFragmentForModuleUnit(ModuleLoc);
-  assert(GlobalModule && "module creation should not fail");
-
-  // Enter the scope of the global module.
-  ModuleScopes.push_back({});
-  ModuleScopes.back().BeginLoc = ModuleLoc;
-  ModuleScopes.back().Module = GlobalModule;
-  VisibleModules.setVisible(GlobalModule, ModuleLoc);
+  auto *GlobalModule =
+      PushGlobalModuleFragment(ModuleLoc, /*IsImplicit=*/false);
----------------
`Module *`


================
Comment at: clang/lib/Sema/SemaModule.cpp:707-708
+                                       bool IsImplicit) {
+  auto &Map = PP.getHeaderSearchInfo().getModuleMap();
+  auto *GlobalModule = Map.createGlobalModuleFragmentForModuleUnit(BeginLoc);
+  assert(GlobalModule && "module creation should not fail");
----------------
Please spell these out as well.


================
Comment at: clang/lib/Sema/SemaModule.cpp:712-715
+  ModuleScopes.push_back({});
+  ModuleScopes.back().BeginLoc = BeginLoc;
+  ModuleScopes.back().Module = GlobalModule;
+  ModuleScopes.back().ImplicitGlobalModuleFragment = IsImplicit;
----------------
Can we use `emplace_back()` and construct in place rather than constructing piecemeal?


================
Comment at: clang/lib/Sema/SemaModule.cpp:722-723
+void Sema::PopGlobalModuleFragment() {
+  assert(!ModuleScopes.empty() && getCurrentModule().isGlobalModule() &&
+         "left the wrong module scope, which is not global module fragment");
+  ModuleScopes.pop_back();
----------------
FWIW, this seems to be failing to compile according to the precommit CI.
```
FAILED: tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaModule.cpp.o
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/clang++ -DBUILD_EXAMPLES -DCLANG_ROUND_TRIP_CC1_ARGS=ON -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Itools/clang/lib/Sema -I/var/lib/buildkite-agent/builds/llvm-project/clang/lib/Sema -I/var/lib/buildkite-agent/builds/llvm-project/clang/include -Itools/clang/include -Iinclude -I/var/lib/buildkite-agent/builds/llvm-project/llvm/include -gmlt -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -fdiagnostics-color -ffunction-sections -fdata-sections -fno-common -Woverloaded-virtual -Wno-nested-anon-types -O3 -DNDEBUG  -fno-exceptions -fno-rtti -UNDEBUG -std=c++14 -MD -MT tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaModule.cpp.o -MF tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaModule.cpp.o.d -o tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/SemaModule.cpp.o -c /var/lib/buildkite-agent/builds/llvm-project/clang/lib/Sema/SemaModule.cpp
/var/lib/buildkite-agent/builds/llvm-project/clang/lib/Sema/SemaModule.cpp:722:53: error: member reference type 'clang::Module *' is a pointer; did you mean to use '->'?
  assert(!ModuleScopes.empty() && getCurrentModule().isGlobalModule() &&
                                  ~~~~~~~~~~~~~~~~~~^
                                                    ->
/usr/include/assert.h:93:27: note: expanded from macro 'assert'
     (static_cast <bool> (expr)                                         \
                          ^~~~
1 error generated.
```


================
Comment at: clang/test/CXX/module/module.linkage_specification/p1.cpp:1
+// RUN: %clang_cc1 -std=c++2a %s -verify
+// expected-no-diagnostics
----------------
Might as well switch all these to use `-std=c++20`.


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  https://reviews.llvm.org/D110215/new/

https://reviews.llvm.org/D110215