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

[Patrick Palka <ppalka@redhat.com>]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

-- >8 --

The unreduced testcase from this PR 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
destructing the call result (which contains an std::string member).

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

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/namespace-6_a.H: New test.
	* g++.dg/modules/namespace-6_b.C: New test.
---
 gcc/cp/module.cc                             | 32 ++++++++++++++++++++
 gcc/testsuite/g++.dg/modules/namespace-6_a.H | 10 ++++++
 gcc/testsuite/g++.dg/modules/namespace-6_b.C |  7 +++++
 3 files changed, 49 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/modules/namespace-6_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/namespace-6_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index d9e34e9a4b9..ce62c3341a6 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -15411,6 +15411,22 @@ 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 tags = lookup_attribute ("abi_tag", DECL_ATTRIBUTES (ns)))
+	    {
+	      tags = TREE_VALUE (tags);
+	      unsigned count = 0;
+	      for (tree tag = tags; tag; tag = TREE_CHAIN (tag))
+		++count;
+	      sec.u (count);
+	      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);
@@ -15441,6 +15457,7 @@ 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
@@ -15449,6 +15466,17 @@ module_state::read_namespaces (unsigned num)
       if (sec.get_overrun ())
 	break;
 
+      tree tags = NULL_TREE;
+      while (tags_count--)
+	{
+	  size_t len;
+	  const char *str = sec.str (&len);
+	  if (sec.get_overrun ())
+	    break;
+	  tags = tree_cons (NULL_TREE, build_string (len + 1, str), tags);
+	  tags = nreverse (tags);
+	}
+
       tree id = name ? get_identifier (from ()->name (name)) : NULL_TREE;
 
       dump () && dump ("Read namespace:%u %P%s%s%s%s",
@@ -15477,6 +15505,10 @@ 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/namespace-6_a.H b/gcc/testsuite/g++.dg/modules/namespace-6_a.H
new file mode 100644
index 00000000000..b412cbe6cbf
--- /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 00000000000..2ce41c7c9c7
--- /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 } }
-- 
2.44.0.117.g43072b4ca1