From 2a8565fa1182ed326721a50c700f9f5275355d40 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Tue, 19 May 2020 23:53:28 -0400 Subject: [PATCH] c++: Implement DR 2289, Uniqueness of structured binding names [PR94553] DR 2289 clarified that since structured bindings have no C compatibility implications, they should be unique in their declarative region, see [basic.scope.declarative]/4.2. The duplicate_decls hunk is the gist of the patch, but that alone would not be enough to detect the 'A' case: cp_parser_decomposition_declaration uses 13968 tree decl2 = start_decl (declarator, &decl_specs, SD_INITIALIZED, 13969 NULL_TREE, NULL_TREE, &elt_pushed_scope); to create the 'A' VAR_DECL but in this start_decl's grokdeclarator we don't do fit_decomposition_lang_decl because the declarator kind is not cdk_decomp, so then when start_decl calls maybe_push_decl, the decl 'A' isn't DECL_DECOMPOSITION_P and we don't detect this case. So I needed a way to signal to start_decl that it should fit_decomposition_lang_decl. In this patch, I'm adding SD_DECOMPOSITION flag to say that the variable is initialized and it should also be marked as DECL_DECOMPOSITION_P. DR 2289 PR c++/94553 * cp-tree.h (SD_DECOMPOSITION): New flag. * decl.c (duplicate_decls): Make sure a structured binding is unique in its declarative region. (start_decl): If INITIALIZED is SD_DECOMPOSITION, call fit_decomposition_lang_decl. (grokdeclarator): Compare INITIALIZED directly to SD_* flags. * parser.c (cp_parser_decomposition_declaration): Pass SD_DECOMPOSITION to start_decl. * g++.dg/cpp1z/decomp52.C: New test. --- gcc/cp/ChangeLog | 13 +++++++++++++ gcc/cp/cp-tree.h | 6 ++++-- gcc/cp/decl.c | 27 +++++++++++++++++---------- gcc/cp/parser.c | 2 +- gcc/testsuite/ChangeLog | 6 ++++++ gcc/testsuite/g++.dg/cpp1z/decomp52.C | 14 ++++++++++++++ 6 files changed, 55 insertions(+), 13 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1z/decomp52.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index c59137faa3f..9ed4c58b403 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,16 @@ +2020-05-20 Marek Polacek + + DR 2289 + PR c++/94553 + * cp-tree.h (SD_DECOMPOSITION): New flag. + * decl.c (duplicate_decls): Make sure a structured binding is unique + in its declarative region. + (start_decl): If INITIALIZED is SD_DECOMPOSITION, call + fit_decomposition_lang_decl. + (grokdeclarator): Compare INITIALIZED directly to SD_* flags. + * parser.c (cp_parser_decomposition_declaration): Pass SD_DECOMPOSITION + to start_decl. + 2020-05-20 Patrick Palka PR c++/95223 diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 31c30ff87b3..27707abaadc 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -5694,8 +5694,10 @@ enum overload_flags { NO_SPECIAL = 0, DTOR_FLAG, TYPENAME_FLAG }; /* Used with start_decl's initialized parameter. */ #define SD_UNINITIALIZED 0 #define SD_INITIALIZED 1 -#define SD_DEFAULTED 2 -#define SD_DELETED 3 +/* Like SD_INITIALIZED, but also mark the new decl as DECL_DECOMPOSITION_P. */ +#define SD_DECOMPOSITION 2 +#define SD_DEFAULTED 3 +#define SD_DELETED 4 /* Returns nonzero iff TYPE1 and TYPE2 are the same type, or if TYPE2 is derived from TYPE1, or if TYPE2 is a pointer (reference) to a diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 6469850e2dc..024ddc88a4c 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -1705,6 +1705,9 @@ duplicate_decls (tree newdecl, tree olddecl, bool newdecl_is_friend) inform (olddecl_loc, "previous declaration %q#D", olddecl); return error_mark_node; } + else if ((VAR_P (olddecl) && DECL_DECOMPOSITION_P (olddecl)) + || (VAR_P (newdecl) && DECL_DECOMPOSITION_P (newdecl))) + /* A structured binding must be unique in its declarative region. */; else if (DECL_IMPLICIT_TYPEDEF_P (olddecl) || DECL_IMPLICIT_TYPEDEF_P (newdecl)) /* One is an implicit typedef, that's ok. */ @@ -5190,13 +5193,17 @@ groktypename (cp_decl_specifier_seq *type_specifiers, declarations appearing in the body of the class go through grokfield.) The DECL corresponding to the DECLARATOR is returned. If an error occurs, the error_mark_node is returned instead. - + DECLSPECS are the decl-specifiers for the declaration. INITIALIZED is SD_INITIALIZED if an explicit initializer is present, or SD_DEFAULTED for an explicitly defaulted function, or SD_DELETED for an explicitly deleted function, but 0 (SD_UNINITIALIZED) if this is a variable - implicitly initialized via a default constructor. ATTRIBUTES and - PREFIX_ATTRIBUTES are GNU attributes associated with this declaration. + implicitly initialized via a default constructor. It can also be + SD_DECOMPOSITION which behaves much like SD_INITIALIZED, but we also + mark the new decl as DECL_DECOMPOSITION_P. + + ATTRIBUTES and PREFIX_ATTRIBUTES are GNU attributes associated with this + declaration. The scope represented by the context of the returned DECL is pushed (if it is not the global namespace) and is assigned to @@ -5232,11 +5239,7 @@ start_decl (const cp_declarator *declarator, if (context != global_namespace) *pushed_scope_p = push_scope (context); - /* Is it valid for this decl to have an initializer at all? - If not, set INITIALIZED to zero, which will indirectly - tell `cp_finish_decl' to ignore the initializer once it is parsed. */ - if (initialized - && TREE_CODE (decl) == TYPE_DECL) + if (initialized && TREE_CODE (decl) == TYPE_DECL) { error_at (DECL_SOURCE_LOCATION (decl), "typedef %qD is initialized (use %qs instead)", @@ -5389,6 +5392,10 @@ start_decl (const cp_declarator *declarator, decl); } + /* Create a DECL_LANG_SPECIFIC so that DECL_DECOMPOSITION_P works. */ + if (initialized == SD_DECOMPOSITION) + fit_decomposition_lang_decl (decl, NULL_TREE); + was_public = TREE_PUBLIC (decl); /* Enter this declaration into the symbol table. Don't push the plain @@ -10997,7 +11004,7 @@ grokdeclarator (const cp_declarator *declarator, else if (decl_context == TPARM) template_parm_flag = true, decl_context = PARM; - if (initialized > 1) + if (initialized == SD_DEFAULTED || initialized == SD_DELETED) funcdef_flag = true; location_t typespec_loc = smallest_type_location (type_quals, @@ -13304,7 +13311,7 @@ grokdeclarator (const cp_declarator *declarator, || (!dependent_type_p (type) && !COMPLETE_TYPE_P (complete_type (type)) && (!complete_or_array_type_p (type) - || initialized == 0)))) + || initialized == SD_UNINITIALIZED)))) { if (TREE_CODE (type) != ARRAY_TYPE || !COMPLETE_TYPE_P (TREE_TYPE (type))) diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index e944841f5a3..a6a5d975af3 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -13974,7 +13974,7 @@ cp_parser_decomposition_declaration (cp_parser *parser, declarator->id_loc = e.get_location (); } tree elt_pushed_scope; - tree decl2 = start_decl (declarator, &decl_specs, SD_INITIALIZED, + tree decl2 = start_decl (declarator, &decl_specs, SD_DECOMPOSITION, NULL_TREE, NULL_TREE, &elt_pushed_scope); if (decl2 == error_mark_node) decl = error_mark_node; diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 9d04b2d4b14..9e437af7452 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2020-05-20 Marek Polacek + + DR 2289 + PR c++/94553 + * g++.dg/cpp1z/decomp52.C: New test. + 2020-05-20 Uroš Bizjak PR target/95229 diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp52.C b/gcc/testsuite/g++.dg/cpp1z/decomp52.C new file mode 100644 index 00000000000..43b76181b5e --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/decomp52.C @@ -0,0 +1,14 @@ +// DR 2289 +// PR c++/94553 +// { dg-do compile { target c++17 } } +// A structured binding must be unique in its declarative region. + +void +f () +{ + int arr[1] = { 1 }; + struct A { }; + auto [A] = arr; // { dg-error "redeclared as different kind of entity" } + auto [B] = arr; + struct B { }; // { dg-error "redeclared as different kind of entity" } +} -- 2.30.2