PR c++/91476 - anon-namespace reference temp clash between TUs.

The problem in the PR was that make_temporary_var_for_ref_to_temp ran before
determine_visibility, so when we copied the linkage of the reference
variable it had not yet been restricted by its anonymous namespace context,
so the temporary wrongly ended up with TREE_PUBLIC set.  The natural
solution is to run determine_visibility earlier.  But that needs to happen
after maybe_commonize_var increases the linkage of some local variables, and
on targets without weak symbol support, that function does different things
based on the results of check_initializer, which is what calls
make_temporary_var_for_ref_to_temp.  To break this circular dependency I'm
calling maybe_commonize_var early, and then again later if the target
doesn't support weak symbols.

It also occurred to me that make_temporary_var_for_ref_to_temp wasn't
handling DECL_VISIBILITY at all, and verified that we were doing the wrong
thing.  So I've combined the linkage-copying code from there and two other
places.

	* decl2.c (copy_linkage): Factor out of get_guard.
	* call.c (make_temporary_var_for_ref_to_temp): Use it.
	* decl.c (cp_finish_decomp): Use it.
	(cp_finish_decl): determine_visibility sooner.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2dda8008f04d8a5ff9934b7aefd4bebacd9cd6ab..412702f9b62691213f492adf142170b820a6fd38 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2020-01-21  Jason Merrill  <jason@redhat.com>
+
+       PR c++/91476 - anon-namespace reference temp clash between TUs.
+       * decl2.c (copy_linkage): Factor out of get_guard.
+       * call.c (make_temporary_var_for_ref_to_temp): Use it.
+       * decl.c (cp_finish_decomp): Use it.
+       (cp_finish_decl): determine_visibility sooner.
+
 2020-01-21  Bin Cheng  <bin.cheng@linux.alibaba.com>
 
        * coroutines.cc (finish_co_await_expr): Set return value flag.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index d47747117b9344f7c92e317ffbed2e67c7e0c013..aacd961faa17ad7e95a46b11d5c8f86a6b740d6b 100644 (file)
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -11973,14 +11973,7 @@ make_temporary_var_for_ref_to_temp (tree decl, tree type)
         GR and suffixed with a sequence number mangled using the usual rules
         for a seq-id. Temporaries are numbered with a pre-order, depth-first,
         left-to-right walk of the complete initializer.  */
-
-      TREE_STATIC (var) = TREE_STATIC (decl);
-      TREE_PUBLIC (var) = TREE_PUBLIC (decl);
-      if (vague_linkage_p (decl))
-       comdat_linkage (var);
-
-      CP_DECL_THREAD_LOCAL_P (var) = CP_DECL_THREAD_LOCAL_P (decl);
-      set_decl_tls_model (var, DECL_TLS_MODEL (decl));
+      copy_linkage (var, decl);
 
       tree name = mangle_ref_init_variable (decl);
       DECL_NAME (var) = name;

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 890d5a2735090d30d283c50172aee0817a8d61e0..77bcf0466089856cb9070a7e7f74a54c8cbd6cef 100644 (file)
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6636,6 +6636,7 @@ extern bool mark_used                             (tree);
 extern bool mark_used                          (tree, tsubst_flags_t);
 extern void finish_static_data_member_decl     (tree, tree, bool, tree, int);
 extern tree cp_build_parm_decl                 (tree, tree, tree);
+extern void copy_linkage                       (tree, tree);
 extern tree get_guard                          (tree);
 extern tree get_guard_cond                     (tree, bool);
 extern tree set_guard                          (tree);

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 28a79029d921e342056fafdbb748c9abf1ec8708..47ff7eea88f1ebe42eeac7b6cc9ad51c8cf11f2a 100644 (file)
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7657,6 +7657,14 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       TREE_READONLY (decl) = 0;
     }
 
+  /* This needs to happen before extend_ref_init_temps.  */
+  if (VAR_OR_FUNCTION_DECL_P (decl))
+    {
+      if (VAR_P (decl))
+       maybe_commonize_var (decl);
+      determine_visibility (decl);
+    }
+
   if (VAR_P (decl))
     {
       duration_kind dk = decl_storage_duration (decl);
@@ -7786,12 +7794,11 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       if (VAR_P (decl))
        {
          layout_var_decl (decl);
-         maybe_commonize_var (decl);
+         if (!flag_weak)
+           /* Check again now that we have an initializer.  */
+           maybe_commonize_var (decl);
        }
 
-      /* This needs to happen after the linkage is set. */
-      determine_visibility (decl);
-
       if (var_definition_p && TREE_STATIC (decl))
        {
          /* If a TREE_READONLY variable needs initialization
@@ -8328,23 +8335,7 @@ cp_finish_decomp (tree decl, tree first, unsigned int count)
            }
          if (!processing_template_decl)
            {
-             TREE_PUBLIC (v[i]) = TREE_PUBLIC (decl);
-             TREE_STATIC (v[i]) = TREE_STATIC (decl);
-             DECL_COMMON (v[i]) = DECL_COMMON (decl);
-             DECL_COMDAT (v[i]) = DECL_COMDAT (decl);
-             if (TREE_STATIC (v[i]))
-               {
-                 CP_DECL_THREAD_LOCAL_P (v[i])
-                   = CP_DECL_THREAD_LOCAL_P (decl);
-                 set_decl_tls_model (v[i], DECL_TLS_MODEL (decl));
-                 if (DECL_ONE_ONLY (decl))
-                   make_decl_one_only (v[i], cxx_comdat_group (v[i]));
-                 if (TREE_PUBLIC (decl))
-                   DECL_WEAK (v[i]) = DECL_WEAK (decl);
-                 DECL_VISIBILITY (v[i]) = DECL_VISIBILITY (decl);
-                 DECL_VISIBILITY_SPECIFIED (v[i])
-                   = DECL_VISIBILITY_SPECIFIED (decl);
-               }
+             copy_linkage (v[i], decl);
              cp_finish_decl (v[i], init, /*constexpr*/false,
                              /*asm*/NULL_TREE, LOOKUP_NORMAL);
            }

diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 042d6fa12df2866ab20d31bb6d3183604d6c3649..1ecf0b937d533dccfbf1614d979fc74786688e89 100644 (file)
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -3214,6 +3214,29 @@ build_cleanup (tree decl)
   return clean;
 }
 
+/* GUARD is a helper variable for DECL; make them have the same linkage and
+   visibility.  */
+
+void
+copy_linkage (tree guard, tree decl)
+{
+  TREE_PUBLIC (guard) = TREE_PUBLIC (decl);
+  TREE_STATIC (guard) = TREE_STATIC (decl);
+  DECL_COMMON (guard) = DECL_COMMON (decl);
+  DECL_COMDAT (guard) = DECL_COMDAT (decl);
+  if (TREE_STATIC (guard))
+    {
+      CP_DECL_THREAD_LOCAL_P (guard) = CP_DECL_THREAD_LOCAL_P (decl);
+      set_decl_tls_model (guard, DECL_TLS_MODEL (decl));
+      /* We can't rely on DECL_WEAK (decl) or DECL_ONE_ONLY (decl) here, as
+        they may not be set until import_export_decl at EOF.  */
+      if (vague_linkage_p (decl))
+       comdat_linkage (guard);
+      DECL_VISIBILITY (guard) = DECL_VISIBILITY (decl);
+      DECL_VISIBILITY_SPECIFIED (guard) = DECL_VISIBILITY_SPECIFIED (decl);
+    }
+}
+
 /* Returns the initialization guard variable for the variable DECL,
    which has static storage duration.  */
 
@@ -3236,18 +3259,7 @@ get_guard (tree decl)
                          VAR_DECL, sname, guard_type);
 
       /* The guard should have the same linkage as what it guards.  */
-      TREE_PUBLIC (guard) = TREE_PUBLIC (decl);
-      TREE_STATIC (guard) = TREE_STATIC (decl);
-      DECL_COMMON (guard) = DECL_COMMON (decl);
-      DECL_COMDAT (guard) = DECL_COMDAT (decl);
-      CP_DECL_THREAD_LOCAL_P (guard) = CP_DECL_THREAD_LOCAL_P (decl);
-      set_decl_tls_model (guard, DECL_TLS_MODEL (decl));
-      if (DECL_ONE_ONLY (decl))
-       make_decl_one_only (guard, cxx_comdat_group (guard));
-      if (TREE_PUBLIC (decl))
-       DECL_WEAK (guard) = DECL_WEAK (decl);
-      DECL_VISIBILITY (guard) = DECL_VISIBILITY (decl);
-      DECL_VISIBILITY_SPECIFIED (guard) = DECL_VISIBILITY_SPECIFIED (decl);
+      copy_linkage (guard, decl);
 
       DECL_ARTIFICIAL (guard) = 1;
       DECL_IGNORED_P (guard) = 1;

diff --git a/gcc/testsuite/g++.dg/ext/visibility/ref-temp1.C b/gcc/testsuite/g++.dg/ext/visibility/ref-temp1.C
new file mode 100644 (file)
index 0000000..ecb6232
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/visibility/ref-temp1.C
@@ -0,0 +1,17 @@
+// PR c++/91476
+// Test that hidden and internal visibility propagates to reference temps.
+
+#define HIDDEN __attribute((visibility("hidden")))
+
+// { dg-final { scan-hidden "_ZGRZ1fvE3foo_" } }
+HIDDEN inline const int* f() { static const int &foo = 1; return &foo; }
+
+// { dg-final { scan-assembler-not "(weak|globl)\[^\n\]*_ZGRN12_GLOBAL__N_13fooE_" } }
+namespace { const int &foo = 1; }
+
+const void *volatile p;
+int main()
+{
+  p = f();
+  p = &foo;
+}