[PATCH] c++/modules: Remember that header units have CMIs

[Nathaniel Shead <nathanieloshead@gmail.com>]

Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?

-- >8 --

This appears to be an oversight in the definition of module_has_cmi_p;
this comes up transitively in other functions used for e.g. determining
whether a name could potentially be accessed in a different translation
unit.

This change will allow us to use the function directly in more places
that need to additional work only if generating a module CMI in the
future.

gcc/cp/ChangeLog:

	* cp-tree.h (module_has_cmi_p): Also true for header units.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/linkage-3_a.H: New test.
	* g++.dg/modules/linkage-3_b.C: New test.
	* g++.dg/modules/linkage-3_c.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/cp-tree.h                           |  2 +-
 gcc/testsuite/g++.dg/modules/linkage-3_a.H | 19 +++++++++++++++++++
 gcc/testsuite/g++.dg/modules/linkage-3_b.C |  9 +++++++++
 gcc/testsuite/g++.dg/modules/linkage-3_c.C | 10 ++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/linkage-3_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/linkage-3_b.C
 create mode 100644 gcc/testsuite/g++.dg/modules/linkage-3_c.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index db098c32f2d..609904918ba 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7379,7 +7379,7 @@ inline bool module_interface_p ()
 inline bool module_partition_p ()
 { return module_kind & MK_PARTITION; }
 inline bool module_has_cmi_p ()
-{ return module_kind & (MK_INTERFACE | MK_PARTITION); }
+{ return module_kind & (MK_INTERFACE | MK_PARTITION | MK_HEADER); }
 
 inline bool module_purview_p ()
 { return module_kind & MK_PURVIEW; }
diff --git a/gcc/testsuite/g++.dg/modules/linkage-3_a.H b/gcc/testsuite/g++.dg/modules/linkage-3_a.H
new file mode 100644
index 00000000000..1e0ebd927e2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/linkage-3_a.H
@@ -0,0 +1,19 @@
+// { dg-additional-options "-fmodule-header -Wno-error=c++20-extensions" }
+// { dg-module-cmi {} }
+
+// Like linkage-1, but for header units.
+
+// External linkage definitions must be declared as 'inline' to satisfy
+// [module.import] p6, so we don't need to care about voldemort types in
+// function definitions.
+
+// Strictly speaking this is not required to be supported:
+// [module.import] p5 says that when two different TUs import header-names
+// identifying the same header or source file, it is unspecified whether
+// they import the same header unit, and thus 's' could be a different entity
+// in each TU.  But with out current implementation this seems to reasonable to
+// allow (and it does currently work).
+
+struct { int y; } s;
+decltype(s) f();  // { dg-warning "used but not defined" "" { target c++17_down } }
+inline auto x = f();
diff --git a/gcc/testsuite/g++.dg/modules/linkage-3_b.C b/gcc/testsuite/g++.dg/modules/linkage-3_b.C
new file mode 100644
index 00000000000..935ef6150ec
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/linkage-3_b.C
@@ -0,0 +1,9 @@
+// { dg-additional-options "-fmodules-ts" }
+
+struct {} unrelated;
+
+import "linkage-3_a.H";
+
+decltype(s) f() {
+  return { 123 };
+}
diff --git a/gcc/testsuite/g++.dg/modules/linkage-3_c.C b/gcc/testsuite/g++.dg/modules/linkage-3_c.C
new file mode 100644
index 00000000000..be527ff552d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/linkage-3_c.C
@@ -0,0 +1,10 @@
+// { dg-module-do run }
+// { dg-additional-options "-fmodules-ts" }
+
+import "linkage-3_a.H";
+
+int main() {
+  auto a = x.y;
+  if (a != 123)
+    __builtin_abort();
+}
-- 
2.43.2