c++/modules: Handle gnu_inline attribute, cleanup linkage determination [PR119154]

Currently, note_vague_linkage_fn is called on all definitions imported
from modules.  This is not correct, however; among other things, a
gnu_inline function does not have vague linkage, and causes an ICE if
its treated as such.

There are other things that we seem to potentially miss (e.g. dllexport
handling), so it seems sensible to stop trying to manage linkage in such
an ad-hoc manner but to use the normal interfaces more often.  While
looking at this I also found that we seem to miss marking vague linkage
variables as COMDAT, so this patch fixes that as well.

The change to use expand_or_defer_fn exposes a checking-only ICE in
trees_in::assert_definition, where we forget that we already installed a
definition for a function.  We work around this by instead of clearing
DECL_SAVED_TREE entirely in expand_or_defer_fn_1, we instead set it to a
dummy value.  This way we can also avoid the check for !TREE_ASM_WRITTEN
beforehand.

	PR c++/119154

gcc/cp/ChangeLog:

	* decl2.cc (vague_linkage_p): Don't treat gnu_inline functions
	as having vague linkage.
	* module.cc (trees_out::core_bools): Clear DECL_INTERFACE_KNOWN
	for vague-linkage entities.
	(read_var_def): Maybe set comdat linkage for imported var
	definitions.
	(module_state::read_cluster): Use expand_or_defer_fn instead of
	ad-hoc linkage management.
	(post_load_processing): Likewise.
	* semantics.cc (expand_or_defer_fn_1): Don't forget that we had
	a definition at all.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/linkage-3_a.C: New test.
	* g++.dg/modules/linkage-3_b.C: New test.
	* g++.dg/modules/pr119154_a.C: New test.
	* g++.dg/modules/pr119154_b.C: New test.

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

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index fe9c56b6637326ede6e76fe02a7934548504826e..4a9fb1c3c00cd8241805b1993c7794baadda5426 100644 (file)
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -2482,7 +2482,9 @@ vague_linkage_p (tree decl)
      DECL_COMDAT.  */
   if (DECL_COMDAT (decl)
       || (TREE_CODE (decl) == FUNCTION_DECL
-         && DECL_DECLARED_INLINE_P (decl))
+         && DECL_DECLARED_INLINE_P (decl)
+         /* But gnu_inline functions are always external.  */
+         && !lookup_attribute ("gnu_inline", DECL_ATTRIBUTES (decl)))
       || (DECL_LANG_SPECIFIC (decl)
          && DECL_TEMPLATE_INSTANTIATION (decl))
       || (VAR_P (decl) && DECL_INLINE_VAR_P (decl)))

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 9a1cd5244c2c57c8440a867839ad3a27230729b5..a17d8433e34c03cf0aa610056b8fbd32b276c9f4 100644 (file)
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -5657,10 +5657,10 @@ trees_out::core_bools (tree t, bits_out& bits)
 
       {
        /* This is DECL_INTERFACE_KNOWN: We should redetermine whether
-          we need to import or export any vtables or typeinfo objects
-          on stream-in.  */
+          we need to import or export any vague-linkage entities on
+          stream-in.  */
        bool interface_known = t->decl_common.lang_flag_5;
-       if (VAR_P (t) && (DECL_VTABLE_OR_VTT_P (t) || DECL_TINFO_P (t)))
+       if (interface_known && vague_linkage_p (t))
          interface_known = false;
        WB (interface_known);
       }
@@ -12616,6 +12616,7 @@ trees_in::read_var_def (tree decl, tree maybe_template)
   bool installing = maybe_dup && !initialized;
   if (installing)
     {
+      DECL_INITIAL (decl) = init;
       if (DECL_EXTERNAL (decl))
        DECL_NOT_REALLY_EXTERN (decl) = true;
       if (VAR_P (decl))
@@ -12623,13 +12624,13 @@ trees_in::read_var_def (tree decl, tree maybe_template)
          DECL_INITIALIZED_P (decl) = true;
          if (maybe_dup && DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (maybe_dup))
            DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl) = true;
+         tentative_decl_linkage (decl);
          if (DECL_IMPLICIT_INSTANTIATION (decl)
              || (DECL_CLASS_SCOPE_P (decl)
                  && !DECL_VTABLE_OR_VTT_P (decl)
                  && !DECL_TEMPLATE_INFO (decl)))
            note_vague_linkage_variable (decl);
        }
-      DECL_INITIAL (decl) = init;
       if (!dyn_init)
        ;
       else if (CP_DECL_THREAD_LOCAL_P (decl))
@@ -16534,12 +16535,7 @@ module_state::read_cluster (unsigned snum)
          cfun->returns_pcc_struct = aggr;
 #endif
          cfun->returns_struct = aggr;
-
-         if (DECL_COMDAT (decl))
-           // FIXME: Comdat grouping?
-           comdat_linkage (decl);
-         note_vague_linkage_fn (decl);
-         cgraph_node::finalize_function (decl, true);
+         expand_or_defer_fn (decl);
        }
 
     }
@@ -19018,22 +19014,7 @@ post_load_processing ()
       dump () && dump ("Post-load processing of %N", decl);
 
       gcc_checking_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (decl));
-
-      if (DECL_COMDAT (decl))
-       comdat_linkage (decl);
-      if (!TREE_ASM_WRITTEN (decl))
-       {
-         /* Cloning can cause loading -- specifically operator delete for
-            the deleting dtor.  */
-         if (maybe_clone_body (decl))
-           TREE_ASM_WRITTEN (decl) = 1;
-         else
-           {
-             /* We didn't clone the cdtor, make sure we emit it.  */
-             note_vague_linkage_fn (decl);
-             cgraph_node::finalize_function (decl, true);
-           }
-       }
+      expand_or_defer_fn (decl);
     }
 
   cfun = old_cfun;

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 6e10893262ddc711b735de2a96629a66bac80a6b..b0a5f9ad660747f9074404849070915593e67752 100644 (file)
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -5502,7 +5502,7 @@ expand_or_defer_fn_1 (tree fn)
         need it anymore.  */
       if (!DECL_DECLARED_CONSTEXPR_P (fn)
          && !(module_maybe_has_cmi_p () && vague_linkage_p (fn)))
-       DECL_SAVED_TREE (fn) = NULL_TREE;
+       DECL_SAVED_TREE (fn) = void_node;
       return false;
     }
 

diff --git a/gcc/testsuite/g++.dg/modules/linkage-3_a.C b/gcc/testsuite/g++.dg/modules/linkage-3_a.C
new file mode 100644 (file)
index 0000000..2bee9c8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/linkage-3_a.C
@@ -0,0 +1,5 @@
+// { dg-do compile { target *-*-*gnu* } }
+// { dg-additional-options "-fmodules" }
+
+export module M;
+export inline int x = 0;

diff --git a/gcc/testsuite/g++.dg/modules/linkage-3_b.C b/gcc/testsuite/g++.dg/modules/linkage-3_b.C
new file mode 100644 (file)
index 0000000..ae14521
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/linkage-3_b.C
@@ -0,0 +1,9 @@
+// { dg-do compile { target *-*-*gnu* } }
+// { dg-additional-options "-fmodules" }
+// { dg-final { scan-assembler "_ZW1M1x,comdat" } }
+
+import M;
+
+int main() {
+  return x;
+}

diff --git a/gcc/testsuite/g++.dg/modules/pr119154_a.C b/gcc/testsuite/g++.dg/modules/pr119154_a.C
new file mode 100644 (file)
index 0000000..23bd186
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr119154_a.C
@@ -0,0 +1,6 @@
+// PR c++/119154
+// { dg-additional-options "-fmodules" }
+// { dg-module-cmi foo }
+
+export module foo;
+extern "C++" inline __attribute__((__gnu_inline__)) void bar() {}

diff --git a/gcc/testsuite/g++.dg/modules/pr119154_b.C b/gcc/testsuite/g++.dg/modules/pr119154_b.C
new file mode 100644 (file)
index 0000000..1558e71
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr119154_b.C
@@ -0,0 +1,10 @@
+// PR c++/119154
+// { dg-module-do link }
+// { dg-additional-options "-fmodules" }
+
+void bar();
+import foo;
+
+int main() {
+  bar();
+}