Re: [Patch, RFC, c*, ObjC* ] make the translation unit decl avail. via a lang hook

[Richard Guenther <richard dot guenther at gmail dot com>]

On Fri, Oct 29, 2010 at 3:44 PM, IainS <developer@sandoe-acoustics.co.uk> wrote:
> given that my current understanding is:
> (a) we should make vars file-scope by setting DECL_CONTEXT = translation
> unit decl
> (b) there should only be one translation unit decl per TU
> (c) at present none of the FEs export the t_u_d where other parts of the
> machinery can see it.
>
> would the following patch be appropriate?
> (it can be extended to fortran and java, I believe, fairly easily).

Sounds like a hack.  Note that frontends might end up with multiple
TUs (for example for things in fortran modules).  It's a hack because
it's a frontend hook that is only used by the frontend (which means
a single global variable does do it as well, like other FEs do it).

Richard.

> ---
>
> (With this applied I can use
> ?DECL_CONTEXT (decl) = (*lang_hooks.decls.translation_unit_context) ();
>
> ?in each place that it is currently set to NULL in objc-act.c
> ?and also replace the two instances of pushdecl_top_level () with the same.
>
> ?and I get no new test-suite fails for ObjC*
> )
>
> comments?
> Iain
>
>
> Index: gcc/c-family/c-common.h
> ===================================================================
> --- gcc/c-family/c-common.h ? ? (revision 166059)
> +++ gcc/c-family/c-common.h ? ? (working copy)
> @@ -514,6 +514,7 @@ extern tree add_stmt (tree);
> ?extern void push_cleanup (tree, tree, bool);
> ?extern tree pushdecl_top_level (tree);
> ?extern tree pushdecl (tree);
> +extern tree c_translation_unit_decl (void);
> ?extern tree build_modify_expr (location_t, tree, tree, enum tree_code,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? location_t, tree, tree);
> ?extern tree build_indirect_ref (location_t, tree, ref_operator);
> Index: gcc/cp/decl.c
> ===================================================================
> --- gcc/cp/decl.c ? ? ? (revision 166059)
> +++ gcc/cp/decl.c ? ? ? (working copy)
> @@ -3427,6 +3427,19 @@ initialize_predefined_identifiers (void)
> ? ? }
> ?}
>
> +/* The current translation unit. ?*/
> +static GTY(()) tree current_translation_unit = NULL_TREE;
> +
> +/* The function used to return the current t_u_d for the
> + ? translation_unit_context langhook. ?*/
> +
> +tree
> +cp_translation_unit_decl (void)
> +{
> + ?gcc_assert (current_translation_unit);
> + ?return current_translation_unit;
> +}
> +
> ?/* Create the predefined scalar types of C,
> ? ?and some nodes representing standard constants (0, 1, (void *)0).
> ? ?Initialize the global binding level.
> @@ -3452,7 +3465,8 @@ cxx_init_decl_processing (void)
> ? gcc_assert (global_namespace == NULL_TREE);
> ? global_namespace = build_lang_decl (NAMESPACE_DECL, global_scope_name,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?void_type_node);
> - ?DECL_CONTEXT (global_namespace) = build_translation_unit_decl
> (NULL_TREE);
> + ?current_translation_unit = build_translation_unit_decl (NULL_TREE);
> + ?DECL_CONTEXT (global_namespace) = current_translation_unit;
> ? TREE_PUBLIC (global_namespace) = 1;
> ? begin_scope (sk_namespace, global_namespace);
>
> Index: gcc/cp/cp-objcp-common.h
> ===================================================================
> --- gcc/cp/cp-objcp-common.h ? ?(revision 166059)
> +++ gcc/cp/cp-objcp-common.h ? ?(working copy)
> @@ -132,6 +132,8 @@ extern bool cp_function_decl_explicit_p (tree decl
> ?#define LANG_HOOKS_GIMPLIFY_EXPR cp_gimplify_expr
> ?#undef LANG_HOOKS_FUNCTION_DECL_EXPLICIT_P
> ?#define LANG_HOOKS_FUNCTION_DECL_EXPLICIT_P cp_function_decl_explicit_p
> +#undef ?LANG_HOOKS_TUD
> +#define LANG_HOOKS_TUD cp_translation_unit_decl
> ?#undef LANG_HOOKS_OMP_PREDETERMINED_SHARING
> ?#define LANG_HOOKS_OMP_PREDETERMINED_SHARING cxx_omp_predetermined_sharing
> ?#undef LANG_HOOKS_OMP_CLAUSE_DEFAULT_CTOR
> Index: gcc/cp/cp-tree.h
> ===================================================================
> --- gcc/cp/cp-tree.h ? ?(revision 166059)
> +++ gcc/cp/cp-tree.h ? ?(working copy)
> @@ -4764,6 +4764,7 @@ extern tree current_decl_namespace
> ?(void);
>
> ?/* decl.c */
> ?extern tree poplevel ? ? ? ? ? ? ? ? ? ? ? ? ? (int, int, int);
> +extern tree cp_translation_unit_decl ? ? ? ? ? (void);
> ?extern void cxx_init_decl_processing ? ? ? ? ? (void);
> ?enum cp_tree_node_structure_enum cp_tree_node_structure
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?(union lang_tree_node *);
> Index: gcc/c-objc-common.h
> ===================================================================
> --- gcc/c-objc-common.h (revision 166059)
> +++ gcc/c-objc-common.h (working copy)
> @@ -85,6 +85,8 @@ along with GCC; see the file COPYING3. ?If not see
> ?#define LANG_HOOKS_TO_TARGET_CHARSET c_common_to_target_charset
> ?#undef LANG_HOOKS_EXPR_TO_DECL
> ?#define LANG_HOOKS_EXPR_TO_DECL c_expr_to_decl
> +#undef ?LANG_HOOKS_TUD
> +#define LANG_HOOKS_TUD c_translation_unit_decl
>
> ?/* The C front end's scoping structure is very different from
> ? ?that expected by the language-independent code; it is best
> Index: gcc/c-decl.c
> ===================================================================
> --- gcc/c-decl.c ? ? ? ?(revision 166059)
> +++ gcc/c-decl.c ? ? ? ?(working copy)
> @@ -454,6 +454,8 @@ static GTY((deletable)) struct c_binding *binding_
> ? t_->to##_last = f_->from##_last; ? ? ? ? ? ? ? ? ? ? ? ? ? ? \
> ?} while (0)
>
> +static GTY(()) tree current_translation_unit = NULL_TREE;
> +
> ?/* A c_inline_static structure stores details of a static identifier
> ? ?referenced in a definition of a function that may be an inline
> ? ?definition if no subsequent declaration of that function uses
> @@ -528,6 +530,14 @@ static tree grokdeclarator (const struct c_declara
> ?static tree grokparms (struct c_arg_info *, bool);
> ?static void layout_array_type (tree);
>
> +/* Return the translation unit decl for the current TU. ?*/
> +tree
> +c_translation_unit_decl (void)
> +{
> + ?gcc_assert (current_translation_unit);
> + ?return current_translation_unit;
> +}
> +
> ?/* T is a statement. ?Add it to the statement-tree. ?This is the
> ? ?C/ObjC version--C++ has a slightly different version of this
> ? ?function. ?*/
> @@ -1066,8 +1076,7 @@ pop_scope (void)
> ? ? context = current_function_decl;
> ? else if (scope == file_scope)
> ? ? {
> - ? ? ?tree file_decl = build_translation_unit_decl (NULL_TREE);
> - ? ? ?context = file_decl;
> + ? ? ?context = (*lang_hooks.decls.translation_unit_context) ();
> ? ? }
> ? else
> ? ? context = block;
> @@ -3461,6 +3470,9 @@ c_init_decl_processing (void)
>
> ? c_common_nodes_and_builtins ();
>
> + ?/* The current translation unit. ?*/
> + ?current_translation_unit = build_translation_unit_decl (NULL_TREE);
> +
> ? /* In C, comparisons and TRUTH_* expressions have type int. ?*/
> ? truthvalue_type_node = integer_type_node;
> ? truthvalue_true_node = integer_one_node;
> Index: gcc/langhooks.h
> ===================================================================
> --- gcc/langhooks.h ? ? (revision 166059)
> +++ gcc/langhooks.h ? ? (working copy)
> @@ -152,6 +152,9 @@ struct lang_hooks_for_decls
> ? ? ?symbol is already declared, may return a different decl for that
> ? ? ?name. ?*/
> ? tree (*pushdecl) (tree);
> +
> + ?/* To add a decl to 'file scope' set its DECL_CONTEXT to this. ?*/
> + ?tree (*translation_unit_context) (void);
>
> ? /* Returns the chain of decls so far in the current scope level. ?*/
> ? tree (*getdecls) (void);
> Index: gcc/langhooks-def.h
> ===================================================================
> --- gcc/langhooks-def.h (revision 166059)
> +++ gcc/langhooks-def.h (working copy)
> @@ -200,6 +200,7 @@ extern tree lhd_make_node (enum tree_code);
> ?/* Declaration hooks. ?*/
> ?#define LANG_HOOKS_GLOBAL_BINDINGS_P global_bindings_p
> ?#define LANG_HOOKS_PUSHDECL ? ?pushdecl
> +#define LANG_HOOKS_TUD lhd_return_null_tree_v
> ?#define LANG_HOOKS_GETDECLS ? ?getdecls
> ?#define LANG_HOOKS_FUNCTION_DECL_EXPLICIT_P hook_bool_tree_false
> ?#define LANG_HOOKS_WARN_UNUSED_GLOBAL_DECL lhd_warn_unused_global_decl
> @@ -220,6 +221,7 @@ extern tree lhd_make_node (enum tree_code);
> ?#define LANG_HOOKS_DECLS { \
> ? LANG_HOOKS_GLOBAL_BINDINGS_P, \
> ? LANG_HOOKS_PUSHDECL, \
> + ?LANG_HOOKS_TUD, \
> ? LANG_HOOKS_GETDECLS, \
> ? LANG_HOOKS_FUNCTION_DECL_EXPLICIT_P, \
> ? LANG_HOOKS_GENERIC_GENERIC_PARAMETER_DECL_P, \
>
>