From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Fri, 26 Sep 2025 12:10:15 +0000 (+1000)
Subject: c++/modules: Avoid ICE when redefining a type reachable via import [PR122053]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=fa6544ef5f50a824cabeda4906453d4545fbf66f;p=thirdparty%2Fgcc.git

c++/modules: Avoid ICE when redefining a type reachable via import [PR122053]

This shouldn't be an error (see PR c++/99000), but we can at least avoid
the ICE by ensuring that we load any pending type definition before
calling pushdecl, so that we error before committing to filling in the
class definition.

Something like this will probably still be helpful even for implementing
textual deduplication as we now at least ensure check_module_override is
called for this case.

	PR c++/122053

gcc/cp/ChangeLog:

	* name-lookup.cc (pushtag): Load any imported definition of type
	before calling pushdecl.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr122053_a.C: New test.
	* g++.dg/modules/pr122053_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 85c7fcc7a6e..09d16db2ead 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -8597,6 +8597,12 @@ pushtag (tree name, tree type, TAG_how how)
 	}
       else
 	{
+	  /* If an import is going to provide a definition for this tag,
+	     load it now so that we don't get confused later when processing
+	     this tag's definition.  */
+	  if (modules_p ())
+	    lazy_load_pendings (decl);
+
 	  decl = do_pushdecl_with_scope
 	    (decl, b, /*hiding=*/(how == TAG_how::HIDDEN_FRIEND));
 	  if (decl == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/modules/pr122053_a.C b/gcc/testsuite/g++.dg/modules/pr122053_a.C
new file mode 100644
index 00000000000..2a8748c6be0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr122053_a.C
@@ -0,0 +1,10 @@
+// PR c++/122053
+// { dg-additional-options "-fmodules -Wno-global-module" }
+// { dg-module-cmi M }
+
+module;
+struct mytime {
+  long a, b;
+};
+export module M;
+export mytime foo();
diff --git a/gcc/testsuite/g++.dg/modules/pr122053_b.C b/gcc/testsuite/g++.dg/modules/pr122053_b.C
new file mode 100644
index 00000000000..a7084b74040
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr122053_b.C
@@ -0,0 +1,9 @@
+// PR c++/122053
+// { dg-additional-options "-fmodules" }
+// Test we don't ICE when redefining a type coming from an import.
+
+import M;
+struct mytime {  // { dg-bogus "conflicting" "PR99000" { xfail *-*-* } }
+  long a, b;
+};
+mytime m = foo();  // { dg-bogus "" "PR99000" { xfail *-*-* } }