http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41201
Dave Korn <davek at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Last reconfirmed| |2010.12.08 14:10:43 CC| |davek at gcc dot gnu.org AssignedTo|unassigned at gcc dot |davek at gcc dot gnu.org |gnu.org | Ever Confirmed|0 |1 --- Comment #6 from Dave Korn <davek at gcc dot gnu.org> 2010-12-08 14:10:43 UTC --- I stumbled into the underlying cause of this bug while working on dllimport/dllexport attributes. It turns out that the TARGET_INSERT_ATTRIBUTES hook is broken in C++, because of a bit of premature optimisation in the routine gcc/cp/decl2.c#cplus_decl_attributes(). This is a C++-specific wrapper round the core compiler's gcc/attribs.c#decl_attributes() which takes care of deferred attribute handling for templates: /* Like decl_attributes, but handle C++ complexity. */ void cplus_decl_attributes (tree *decl, tree attributes, int flags) { if (*decl == NULL_TREE || *decl == void_type_node || *decl == error_mark_node || attributes == NULL_TREE) return; if (processing_template_decl) { if (check_for_bare_parameter_packs (attributes)) return; save_template_attributes (&attributes, decl); if (attributes == NULL_TREE) return; } if (TREE_CODE (*decl) == TEMPLATE_DECL) decl = &DECL_TEMPLATE_RESULT (*decl); decl_attributes (decl, attributes, flags); if (TREE_CODE (*decl) == TYPE_DECL) SET_IDENTIFIER_TYPE_VALUE (DECL_NAME (*decl), TREE_TYPE (*decl)); } The early exits when attributes == NULL_TREE are (I suppose) intended to save the time taken calling decl_attributes when there aren't any attributes to be added to the newly-created decl, but it has the side-effect of bypassing the call that decl_attributes makes to TARGET_INSERT_ATTRIBUTES. The consequence is that the default/target/pragma-derived attributes don't get inserted onto any decls in C++ - except for decls that have some explicit attributes specified! I'm going to be testing this fix as part of a larger patch over the next couple of days, perhaps others would like to give it a try on their platforms: Index: gcc/cp/decl2.c =================================================================== --- gcc/cp/decl2.c (revision 167484) +++ gcc/cp/decl2.c (working copy) @@ -1269,8 +1269,7 @@ void cplus_decl_attributes (tree *decl, tree attributes, int flags) { if (*decl == NULL_TREE || *decl == void_type_node - || *decl == error_mark_node - || attributes == NULL_TREE) + || *decl == error_mark_node) return; if (processing_template_decl) @@ -1279,13 +1278,13 @@ cplus_decl_attributes (tree *decl, tree attributes return; save_template_attributes (&attributes, decl); - if (attributes == NULL_TREE) - return; } if (TREE_CODE (*decl) == TEMPLATE_DECL) decl = &DECL_TEMPLATE_RESULT (*decl); + /* Even if ATTRIBUTES is null, we must call this in order to + give the TARGET_INSERT_ATTRIBUTES hook a chance to run. */ decl_attributes (decl, attributes, flags); if (TREE_CODE (*decl) == TYPE_DECL)