c++/modules: inline namespace abi_tag streaming [PR110730]

The unreduced testcase from PR110730 crashes at runtime ultimately
because we don't stream the abi_tag attribute on inline namespaces and
so the filesystem::current_path() call resolves to the non-C++11 ABI
version even though the C++11 ABI is active, leading to a crash when
destroying the path temporary (which contains an std::string member).
Similar story for the PR105512 testcase.

While we do stream the DECL_ATTRIBUTES of all decls that go through
the generic tree streaming routines, it seems namespaces are streamed
separately from other decls and we don't use the generic routines for
them.  So this patch makes us stream the abi_tag manually for (inline)
namespaces.

	PR c++/110730
	PR c++/105512

gcc/cp/ChangeLog:

	* module.cc (module_state::write_namespaces): Stream the
	abi_tag attribute of an inline namespace.
	(module_state::read_namespaces): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/hello-2_a.C: New test.
	* g++.dg/modules/hello-2_b.C: New test.
	* g++.dg/modules/namespace-6_a.H: New test.
	* g++.dg/modules/namespace-6_b.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

5 files changed, 66 insertions, 0 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index f7e8b35..d52db76 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -15276,6 +15276,19 @@ module_state::write_namespaces (elf_out *to, vec<depset *> spaces,
 
       sec.u (flags);
       write_location (sec, DECL_SOURCE_LOCATION (ns));
+
+      if (DECL_NAMESPACE_INLINE_P (ns))
+	{
+	  if (tree attr = lookup_attribute ("abi_tag", DECL_ATTRIBUTES (ns)))
+	    {
+	      tree tags = TREE_VALUE (attr);
+	      sec.u (list_length (tags));
+	      for (tree tag = tags; tag; tag = TREE_CHAIN (tag))
+		sec.str (TREE_STRING_POINTER (TREE_VALUE (tag)));
+	    }
+	  else
+	    sec.u (0);
+	}
     }
 
   sec.end (to, to->name (MOD_SNAME_PFX ".nms"), crc_p);
@@ -15306,11 +15319,22 @@ module_state::read_namespaces (unsigned num)
       /* See comment in write_namespace about why not bits.  */
       unsigned flags = sec.u ();
       location_t src_loc = read_location (sec);
+      unsigned tags_count = (flags & 2) ? sec.u () : 0;
 
       if (entity_index >= entity_num
 	  || !parent
 	  || (flags & 0xc) == 0x8)
 	sec.set_overrun ();
+
+      tree tags = NULL_TREE;
+      while (tags_count--)
+	{
+	  size_t len;
+	  const char *str = sec.str (&len);
+	  tags = tree_cons (NULL_TREE, build_string (len + 1, str), tags);
+	  tags = nreverse (tags);
+	}
+
       if (sec.get_overrun ())
 	break;
 
@@ -15342,6 +15366,10 @@ module_state::read_namespaces (unsigned num)
 	    DECL_MODULE_EXPORT_P (inner) = true;
 	}
 
+      if (tags)
+	DECL_ATTRIBUTES (inner)
+	  = tree_cons (get_identifier ("abi_tag"), tags, DECL_ATTRIBUTES (inner));
+
       /* Install the namespace.  */
       (*entity_ary)[entity_lwm + entity_index] = inner;
       if (DECL_MODULE_IMPORT_P (inner))
diff --git a/gcc/testsuite/g++.dg/modules/hello-2_a.C b/gcc/testsuite/g++.dg/modules/hello-2_a.C
new file mode 100644
index 0000000..a8f8b81
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/hello-2_a.C
@@ -0,0 +1,11 @@
+// PR c++/105512
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi Hello2 }
+
+module;
+#include <string>
+export module Hello2;
+
+export std::string tester() {
+  return "hello world\n";
+}
diff --git a/gcc/testsuite/g++.dg/modules/hello-2_b.C b/gcc/testsuite/g++.dg/modules/hello-2_b.C
new file mode 100644
index 0000000..dafd3c2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/hello-2_b.C
@@ -0,0 +1,10 @@
+// PR c++/105512
+// { dg-additional-options -fmodules-ts }
+// { dg-module-do run }
+
+#include <iostream>
+import Hello2;
+
+int main() {
+  std::cout << tester();
+}
diff --git a/gcc/testsuite/g++.dg/modules/namespace-6_a.H b/gcc/testsuite/g++.dg/modules/namespace-6_a.H
new file mode 100644
index 0000000..b412cbe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/namespace-6_a.H
@@ -0,0 +1,10 @@
+// PR c++/110730
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+namespace std::filesystem {
+  inline namespace __cxx11 __attribute__((__abi_tag__("cxx11", "foo"))) {
+    struct path { };
+  }
+  inline path current_path() { return {}; };
+}
diff --git a/gcc/testsuite/g++.dg/modules/namespace-6_b.C b/gcc/testsuite/g++.dg/modules/namespace-6_b.C
new file mode 100644
index 0000000..2ce41c7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/namespace-6_b.C
@@ -0,0 +1,7 @@
+// PR c++/110730
+// { dg-additional-options -fmodules-ts }
+
+import "namespace-6_a.H";
+
+int main() { std::filesystem::current_path(); }
+// { dg-final { scan-assembler _ZNSt10filesystem12current_pathB5cxx11B3fooEv } }