[gcc r13-3299] c++ modules: ICE with dynamic_cast [PR106304]

[Patrick Palka <ppalka@gcc.gnu.org>]

https://gcc.gnu.org/g:d6a488f243acfac4bdbbb0eefbee3ae916159cf5

commit r13-3299-gd6a488f243acfac4bdbbb0eefbee3ae916159cf5
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Oct 14 09:07:01 2022 -0400

    c++ modules: ICE with dynamic_cast [PR106304]
    
    The FUNCTION_DECL we build for __dynamic_cast has an empty DECL_CONTEXT
    but trees_out::tree_node expects FUNCTION_DECLs to have non-empty
    DECL_CONTEXT, thus we crash when streaming out the dynamic_cast in the
    below testcase.
    
    This patch naively fixes this by setting DECL_CONTEXT for __dynamic_cast
    appropriately.  I suppose we should push it into the namespace too, like
    we do for __cxa_atexit which is similarly lazily declared.
    
            PR c++/106304
    
    gcc/cp/ChangeLog:
    
            * constexpr.cc (cxx_dynamic_cast_fn_p): Check for abi_node
            instead of global_namespace.
            * rtti.cc (build_dynamic_cast_1): Set DECL_CONTEXT and
            DECL_SOURCE_LOCATION when building dynamic_cast_node.  Push
            it into the namespace.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/pr106304_a.C: New test.
            * g++.dg/modules/pr106304_b.C: New test.

Diff:
---
 gcc/cp/constexpr.cc                       |  2 +-
 gcc/cp/rtti.cc                            |  4 ++++
 gcc/testsuite/g++.dg/modules/pr106304_a.C | 12 ++++++++++++
 gcc/testsuite/g++.dg/modules/pr106304_b.C |  8 ++++++++
 4 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index fb171a2784f..03663961bb8 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2088,7 +2088,7 @@ cxx_dynamic_cast_fn_p (tree fndecl)
 {
   return (cxx_dialect >= cxx20
 	  && id_equal (DECL_NAME (fndecl), "__dynamic_cast")
-	  && CP_DECL_CONTEXT (fndecl) == global_namespace);
+	  && CP_DECL_CONTEXT (fndecl) == abi_node);
 }
 
 /* Often, we have an expression in the form of address + offset, e.g.
diff --git a/gcc/cp/rtti.cc b/gcc/cp/rtti.cc
index f5b43ec0fb2..a85c7b56409 100644
--- a/gcc/cp/rtti.cc
+++ b/gcc/cp/rtti.cc
@@ -787,6 +787,10 @@ build_dynamic_cast_1 (location_t loc, tree type, tree expr,
 			       NULL_TREE));
 	      dcast_fn = (build_library_fn_ptr
 			  (fn_name, fn_type, ECF_LEAF | ECF_PURE | ECF_NOTHROW));
+	      /* As with __cxa_atexit in get_atexit_node.  */
+	      DECL_CONTEXT (dcast_fn) = FROB_CONTEXT (current_namespace);
+	      DECL_SOURCE_LOCATION (dcast_fn) = BUILTINS_LOCATION;
+	      dcast_fn = pushdecl (dcast_fn, /*hiding=*/true);
 	      pop_abi_namespace (flags);
 	      dynamic_cast_node = dcast_fn;
 	    }
diff --git a/gcc/testsuite/g++.dg/modules/pr106304_a.C b/gcc/testsuite/g++.dg/modules/pr106304_a.C
new file mode 100644
index 00000000000..b999eeccf4a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr106304_a.C
@@ -0,0 +1,12 @@
+// PR c++/106304
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi pr106304 }
+
+export module pr106304;
+
+struct A { virtual ~A() = default; };
+struct B : A { };
+
+inline const B* as_b(const A& a) {
+  return dynamic_cast<const B*>(&a);
+}
diff --git a/gcc/testsuite/g++.dg/modules/pr106304_b.C b/gcc/testsuite/g++.dg/modules/pr106304_b.C
new file mode 100644
index 00000000000..e8333909c8d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr106304_b.C
@@ -0,0 +1,8 @@
+// PR c++/106304
+// { dg-additional-options -fmodules-ts }
+
+module pr106304;
+
+void f(A& a) {
+  as_b(a);
+}