https://gcc.gnu.org/g:79420dd344145819677b3f975bb305a778fcaf91
commit r15-84-g79420dd344145819677b3f975bb305a778fcaf91
Author: Nathaniel Shead <nathanielosh...@gmail.com>
Date: Mon Mar 4 23:58:30 2024 +1100
c++: Implement P2615 'Meaningful Exports' [PR107688]
This clarifies which kinds of declarations may and may not be exported
in various contexts. The patch additionally fixes up some small issues
that were clarified by the paper.
Most of the changes are with regards to export-declarations, which are
applied for all standards modes that we support '-fmodules-ts' for.
However there are also a couple of changes made to linkage specifiers
('extern "C"'); I've applied these as since C++20, to line up with when
modules were actually introduced.
PR c++/107688
gcc/cp/ChangeLog:
* name-lookup.cc (push_namespace): Error when exporting
namespace with internal linkage.
* parser.h (struct cp_parser): Add new flag
'in_unbraced_export_declaration_p'.
* parser.cc (cp_debug_parser): Print the new flag.
(cp_parser_new): Initialise the new flag.
(cp_parser_module_export): Set the new flag.
(cp_parser_class_specifier): Clear and restore the new flag.
(cp_parser_import_declaration): Imports can now appear directly
in a linkage specification.
(cp_parser_declaration): Categorise declarations as "name" or
"special"; error on the later in contexts where the former is
required.
(cp_parser_class_head): Error when exporting a partial
specialisation.
gcc/testsuite/ChangeLog:
* g++.dg/modules/contracts-1_a.C: Avoid now-illegal syntax.
* g++.dg/modules/contracts-2_a.C: Likewise.
* g++.dg/modules/contracts-3_a.C: Likewise.
* g++.dg/modules/contracts-4_a.C: Likewise.
* g++.dg/modules/lang-1_c.C: Clarify now-legal syntax.
* g++.dg/modules/pr101582-1.C: Remove now-legal XFAILS.
* g++.dg/template/crash71.C: Update error messages.
* g++.dg/cpp2a/linkage-spec1.C: New test.
* g++.dg/modules/export-3.C: New test.
* g++.dg/modules/export-4_a.C: New test.
* g++.dg/modules/export-4_b.C: New test.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
Diff:
---
gcc/cp/name-lookup.cc | 10 ++-
gcc/cp/parser.cc | 105 +++++++++++++++++++++------
gcc/cp/parser.h | 6 +-
gcc/testsuite/g++.dg/cpp2a/linkage-spec1.C | 22 ++++++
gcc/testsuite/g++.dg/modules/contracts-1_a.C | 2 +-
gcc/testsuite/g++.dg/modules/contracts-2_a.C | 2 +-
gcc/testsuite/g++.dg/modules/contracts-3_a.C | 2 +-
gcc/testsuite/g++.dg/modules/contracts-4_a.C | 2 +-
gcc/testsuite/g++.dg/modules/export-3.C | 30 ++++++++
gcc/testsuite/g++.dg/modules/export-4_a.C | 23 ++++++
gcc/testsuite/g++.dg/modules/export-4_b.C | 13 ++++
gcc/testsuite/g++.dg/modules/lang-1_c.C | 2 +-
gcc/testsuite/g++.dg/modules/pr101582-1.C | 8 +-
gcc/testsuite/g++.dg/template/crash71.C | 4 +-
14 files changed, 197 insertions(+), 34 deletions(-)
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 4dffc0e9acc..5d2319db43d 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -9143,8 +9143,14 @@ push_namespace (tree name, bool make_inline)
{
/* A public namespace is exported only if explicitly marked, or
it contains exported entities. */
- if (TREE_PUBLIC (ns) && module_exporting_p ())
- DECL_MODULE_EXPORT_P (ns) = true;
+ if (module_exporting_p ())
+ {
+ if (TREE_PUBLIC (ns))
+ DECL_MODULE_EXPORT_P (ns) = true;
+ else if (!header_module_p ())
+ error_at (input_location,
+ "exporting namespace with internal linkage");
+ }
if (module_purview_p ())
DECL_MODULE_PURVIEW_P (ns) = true;
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index aefbffe8330..a2bc6f69000 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -560,6 +560,8 @@ cp_debug_parser (FILE *file, cp_parser *parser)
& THIS_FORBIDDEN));
cp_debug_print_flag (file, "In unbraced linkage specification",
parser->in_unbraced_linkage_specification_p);
+ cp_debug_print_flag (file, "In unbraced export declaration",
+ parser->in_unbraced_export_declaration_p);
cp_debug_print_flag (file, "Parsing a declarator",
parser->in_declarator_p);
cp_debug_print_flag (file, "In template argument list",
@@ -4425,6 +4427,9 @@ cp_parser_new (cp_lexer *lexer)
/* We are not processing an `extern "C"' declaration. */
parser->in_unbraced_linkage_specification_p = false;
+ /* We aren't parsing an export-declaration. */
+ parser->in_unbraced_export_declaration_p = false;
+
/* We are not processing a declarator. */
parser->in_declarator_p = false;
@@ -15249,10 +15254,6 @@ cp_parser_import_declaration (cp_parser *parser,
module_parse mp_state,
goto skip_eol;
cp_parser_require_pragma_eol (parser, token);
- if (parser->in_unbraced_linkage_specification_p)
- error_at (token->location, "import cannot appear directly in"
- " a linkage-specification");
-
if (mp_state == MP_PURVIEW_IMPORTS || mp_state == MP_PRIVATE_IMPORTS)
{
/* Module-purview imports must not be from source inclusion
@@ -15273,7 +15274,7 @@ cp_parser_import_declaration (cp_parser *parser,
module_parse mp_state,
/* export-declaration.
- export declaration
+ export name-declaration
export { declaration-seq-opt } */
static void
@@ -15315,7 +15316,13 @@ cp_parser_module_export (cp_parser *parser)
|| cp_lexer_next_token_is_keyword (parser->lexer, RID__EXPORT))
error_at (token->location, "%<export%> not part of following"
" module-directive");
+
+ bool saved_in_unbraced_export_declaration_p
+ = parser->in_unbraced_export_declaration_p;
+ parser->in_unbraced_export_declaration_p = true;
cp_parser_declaration (parser, NULL_TREE);
+ parser->in_unbraced_export_declaration_p
+ = saved_in_unbraced_export_declaration_p;
}
module_kind = mk;
@@ -15346,27 +15353,29 @@ cp_parser_declaration_seq_opt (cp_parser* parser)
}
}
-/* Parse a declaration.
+/* Parse a declaration. The distinction between name-declaration
+ and special-declaration is only since C++20.
declaration:
+ name-declaration
+ special-declaration
+
+ name-declaration:
block-declaration
+ nodeclspec-function-declaration
function-definition
template-declaration
- explicit-instantiation
- explicit-specialization
+ deduction-guide (C++17)
linkage-specification
namespace-definition
+ empty-declaration
+ attribute-declaration
+ module-import-declaration (modules)
- C++17:
- deduction-guide
-
- modules:
- (all these are only allowed at the outermost level, check
- that semantically, for better diagnostics)
- module-declaration
- module-export-declaration
- module-import-declaration
- export-declaration
+ special-declaration:
+ explicit-instantiation
+ explicit-specialization
+ export-declaration (modules)
GNU extension:
@@ -15389,6 +15398,13 @@ cp_parser_declaration (cp_parser* parser, tree
prefix_attrs)
return;
}
+ /* P2615: Determine if we're parsing a name-declaration specifically,
+ or if special-declarations are OK too. */
+ bool require_name_decl_p
+ = (parser->in_unbraced_export_declaration_p
+ || (parser->in_unbraced_linkage_specification_p
+ && cxx_dialect >= cxx20));
+
/* Try to figure out what kind of declaration is present. */
cp_token *token1 = cp_lexer_peek_token (parser->lexer);
cp_token *token2 = (token1->type == CPP_EOF
@@ -15496,13 +15512,30 @@ cp_parser_declaration (cp_parser* parser, tree
prefix_attrs)
/* `template <>' indicates a template specialization. */
if (token2->type == CPP_LESS
&& cp_lexer_peek_nth_token (parser->lexer, 3)->type == CPP_GREATER)
- cp_parser_explicit_specialization (parser);
+ {
+ if (require_name_decl_p)
+ {
+ auto_diagnostic_group d;
+ cp_token *token3 = cp_lexer_peek_nth_token (parser->lexer, 3);
+ location_t loc = make_location (token1, token1, token3);
+ error_at (loc, "explicit specializations are not permitted here");
+ if (parser->in_unbraced_export_declaration_p)
+ inform (loc, "a specialization is always exported alongside "
+ "its primary template");
+ }
+ cp_parser_explicit_specialization (parser);
+ }
/* `template <' indicates a template declaration. */
else if (token2->type == CPP_LESS)
cp_parser_template_declaration (parser, /*member_p=*/false);
/* Anything else must be an explicit instantiation. */
else
- cp_parser_explicit_instantiation (parser);
+ {
+ if (require_name_decl_p)
+ error_at (token1->location,
+ "explicit instantiations are not permitted here");
+ cp_parser_explicit_instantiation (parser);
+ }
}
/* If the next token is `export', it's new-style modules or
old-style template. */
@@ -15511,7 +15544,14 @@ cp_parser_declaration (cp_parser* parser, tree
prefix_attrs)
if (!modules_p ())
cp_parser_template_declaration (parser, /*member_p=*/false);
else
- cp_parser_module_export (parser);
+ {
+ /* We check for nested exports in cp_parser_module_export. */
+ if (require_name_decl_p
+ && !parser->in_unbraced_export_declaration_p)
+ error_at (token1->location,
+ "export-declarations are not permitted here");
+ cp_parser_module_export (parser);
+ }
}
else if (cp_token_is_module_directive (token1))
{
@@ -16836,7 +16876,7 @@ cp_parser_function_specifier_opt (cp_parser* parser,
linkage-specification:
extern string-literal { declaration-seq [opt] }
- extern string-literal declaration */
+ extern string-literal name-declaration */
static void
cp_parser_linkage_specification (cp_parser* parser, tree prefix_attr)
@@ -26795,6 +26835,7 @@ cp_parser_class_specifier (cp_parser* parser)
unsigned char in_statement;
bool in_switch_statement_p;
bool saved_in_unbraced_linkage_specification_p;
+ bool saved_in_unbraced_export_declaration_p;
tree old_scope = NULL_TREE;
tree scope = NULL_TREE;
cp_token *closing_brace;
@@ -26846,6 +26887,10 @@ cp_parser_class_specifier (cp_parser* parser)
saved_in_unbraced_linkage_specification_p
= parser->in_unbraced_linkage_specification_p;
parser->in_unbraced_linkage_specification_p = false;
+ /* Or in an export-declaration. */
+ saved_in_unbraced_export_declaration_p
+ = parser->in_unbraced_export_declaration_p;
+ parser->in_unbraced_export_declaration_p = false;
/* 'this' from an enclosing non-static member function is unavailable. */
tree saved_ccp = current_class_ptr;
tree saved_ccr = current_class_ref;
@@ -27228,6 +27273,8 @@ cp_parser_class_specifier (cp_parser* parser)
= saved_num_template_parameter_lists;
parser->in_unbraced_linkage_specification_p
= saved_in_unbraced_linkage_specification_p;
+ parser->in_unbraced_export_declaration_p
+ = saved_in_unbraced_export_declaration_p;
current_class_ptr = saved_ccp;
current_class_ref = saved_ccr;
@@ -27515,6 +27562,20 @@ cp_parser_class_head (cp_parser* parser,
permerror (nested_name_specifier_token_start->location,
"extra qualification not allowed");
}
+ /* The name-declaration of an export-declaration shall not declare
+ a partial specialization. */
+ if (template_id_p
+ && parser->in_unbraced_export_declaration_p
+ && !processing_specialization
+ && !processing_explicit_instantiation)
+ {
+ auto_diagnostic_group d;
+ location_t loc = type_start_token->location;
+ error_at (loc, "declaration of partial specialization in unbraced "
+ "export-declaration");
+ inform (loc, "a specialization is always exported alongside its "
+ "primary template");
+ }
/* An explicit-specialization must be preceded by "template <>". If
it is not, try to recover gracefully. */
if (at_namespace_scope_p ()
diff --git a/gcc/cp/parser.h b/gcc/cp/parser.h
index 373e78f3ea4..09b356e5e73 100644
--- a/gcc/cp/parser.h
+++ b/gcc/cp/parser.h
@@ -312,9 +312,13 @@ struct GTY(()) cp_parser {
/* TRUE if the declaration we are parsing is part of a
linkage-specification of the form `extern string-literal
- declaration'. */
+ name-declaration'. */
bool in_unbraced_linkage_specification_p;
+ /* TRUE if the declaration we are parsing is part of an
+ export-declaration of the form 'export name-declaration'. */
+ bool in_unbraced_export_declaration_p;
+
/* TRUE if we are presently parsing a declarator, after the
direct-declarator. */
bool in_declarator_p;
diff --git a/gcc/testsuite/g++.dg/cpp2a/linkage-spec1.C
b/gcc/testsuite/g++.dg/cpp2a/linkage-spec1.C
new file mode 100644
index 00000000000..9e8d5979059
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/linkage-spec1.C
@@ -0,0 +1,22 @@
+// PR c++/107688
+// P2615R1: Meaningful exports: Newly invalid declarations
+// { dg-do compile { target c++11 } }
+
+extern "C++" template <typename T> struct A {};
+
+extern "C++" template <typename T> struct A<T*> {};
+
+extern "C++" template <> struct A<int*> {};
+// { dg-error "explicit specializations are not permitted here" "" { target
c++20 } .-1 }
+
+extern "C++" template struct A<int>;
+// { dg-error "explicit instantiations are not permitted here" "" { target
c++20 } .-1 }
+
+
+// These should all still be valid, though
+extern "C++" {
+ template <typename T> struct B {};
+ template <typename T> struct B<T*> {};
+ template <> struct B<int*> {};
+ template struct B<int>;
+}
diff --git a/gcc/testsuite/g++.dg/modules/contracts-1_a.C
b/gcc/testsuite/g++.dg/modules/contracts-1_a.C
index f991ef8644e..723726451f4 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-1_a.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-1_a.C
@@ -8,7 +8,7 @@ export module foo;
// { dg-module-cmi foo }
export int violation_count{0};
-extern "C++" export void handle_contract_violation(const
std::experimental::contract_violation &violation)
+export extern "C++" void handle_contract_violation(const
std::experimental::contract_violation &violation)
{
violation_count++;
printf("violation_count: %d\n", violation_count);
diff --git a/gcc/testsuite/g++.dg/modules/contracts-2_a.C
b/gcc/testsuite/g++.dg/modules/contracts-2_a.C
index 828d680d2a0..3d78c412d46 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-2_a.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-2_a.C
@@ -12,7 +12,7 @@ export module foo;
export int violation_count{0};
export int violation_line_sum{0};
-extern "C++" export void handle_contract_violation(const
std::experimental::contract_violation &violation)
+export extern "C++" void handle_contract_violation(const
std::experimental::contract_violation &violation)
{
violation_count++;
violation_line_sum += violation.line_number () * violation_count;
diff --git a/gcc/testsuite/g++.dg/modules/contracts-3_a.C
b/gcc/testsuite/g++.dg/modules/contracts-3_a.C
index a4f03d35842..b931ec0ddf7 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-3_a.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-3_a.C
@@ -8,7 +8,7 @@ export module foo;
// { dg-module-cmi foo }
export int violation_count{0};
-extern "C++" export void handle_contract_violation(const
std::experimental::contract_violation &violation)
+export extern "C++" void handle_contract_violation(const
std::experimental::contract_violation &violation)
{
violation_count++;
printf("violation_count: %d\n", violation_count);
diff --git a/gcc/testsuite/g++.dg/modules/contracts-4_a.C
b/gcc/testsuite/g++.dg/modules/contracts-4_a.C
index f269e6c2078..a135f50fb7d 100644
--- a/gcc/testsuite/g++.dg/modules/contracts-4_a.C
+++ b/gcc/testsuite/g++.dg/modules/contracts-4_a.C
@@ -9,7 +9,7 @@ export module foo;
// { dg-module-cmi foo }
export int violation_count{0};
-extern "C++" export void handle_contract_violation(const
std::experimental::contract_violation &violation)
+export extern "C++" void handle_contract_violation(const
std::experimental::contract_violation &violation)
{
violation_count++;
printf("violation_count: %d\n", violation_count);
diff --git a/gcc/testsuite/g++.dg/modules/export-3.C
b/gcc/testsuite/g++.dg/modules/export-3.C
new file mode 100644
index 00000000000..76765fd2b2f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/export-3.C
@@ -0,0 +1,30 @@
+// P2615R1 invalid declarations
+// PR c++/107688
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi !bad }
+
+export module bad;
+
+extern "C++" export void foo(); // { dg-error "export-declarations are not
permitted here" "" { target c++20 } }
+
+export template <typename T> struct S {};
+
+export template <typename T> struct S<T*> {}; // { dg-error "partial
specialization in unbraced export-declaration" }
+
+export template <> struct S<int*> {}; // { dg-error "explicit specializations
are not permitted here" }
+
+export template struct S<int>; // { dg-error "explicit instantiations are not
permitted here" }
+
+template <> export struct S<double>; // { dg-error "expected unqualified-id" }
+
+export export int x; // { dg-error ".export. may only occur once" }
+
+export { export int y; } // { dg-error ".export. may only occur once" }
+
+namespace {
+ export namespace ns {} // { dg-error "internal linkage" }
+}
+
+export namespace {} // { dg-error "internal linkage" }
+
+// { dg-prune-output "not writing module" }
diff --git a/gcc/testsuite/g++.dg/modules/export-4_a.C
b/gcc/testsuite/g++.dg/modules/export-4_a.C
new file mode 100644
index 00000000000..5f99577dc99
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/export-4_a.C
@@ -0,0 +1,23 @@
+// P2615R1 valid declarations
+// PR c++/107688
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi M }
+
+export module M;
+
+export {}
+export { static_assert(true); }
+
+export namespace Empty {}
+export using namespace Empty;
+
+export {
+ template <typename T> struct S {};
+ template <typename T> struct S<T*> { using a = int; };
+ template <> struct S<int*> { using b = int; };
+ template struct S<int>;
+}
+
+extern "C++" {
+ export void foo();
+}
diff --git a/gcc/testsuite/g++.dg/modules/export-4_b.C
b/gcc/testsuite/g++.dg/modules/export-4_b.C
new file mode 100644
index 00000000000..4d721119916
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/export-4_b.C
@@ -0,0 +1,13 @@
+// PR c++/107688
+// { dg-additional-options "-fmodules-ts" }
+
+import M;
+
+using namespace Empty;
+
+int main() {
+ S<int> x;
+ S<int*>::b y;
+ S<int**>::a z;
+ foo();
+}
diff --git a/gcc/testsuite/g++.dg/modules/lang-1_c.C
b/gcc/testsuite/g++.dg/modules/lang-1_c.C
index e3b939df373..b3908ed6188 100644
--- a/gcc/testsuite/g++.dg/modules/lang-1_c.C
+++ b/gcc/testsuite/g++.dg/modules/lang-1_c.C
@@ -6,7 +6,7 @@ extern "C++"
}
extern "C"
-import "lang-1_a.H"; // { dg-error "cannot appear directly" }
+ import "lang-1_a.H"; // OK since p2615r1
extern "C" int cfunc (int); // { dg-error "conflicting declaration" }
extern "C" int cxxfunc (int);
diff --git a/gcc/testsuite/g++.dg/modules/pr101582-1.C
b/gcc/testsuite/g++.dg/modules/pr101582-1.C
index 1d3a3fcb6fa..ec7e44e1f43 100644
--- a/gcc/testsuite/g++.dg/modules/pr101582-1.C
+++ b/gcc/testsuite/g++.dg/modules/pr101582-1.C
@@ -2,8 +2,10 @@
// { dg-additional-options "-fmodules-ts" }
export module pr101582;
// { dg-module-cmi "pr101582" }
-export ; // { dg-error "export declaration does not
declare anything" "" { xfail *-*-* } }
-export [[]]; // { dg-error "export declaration does not
declare anything" "" { xfail *-*-* } }
-export // { dg-error "export declaration does not
declare anything" "" { xfail *-*-* } }
+
+// These are all legal since P2615R1.
+export ;
+export [[]];
+export
{
}
diff --git a/gcc/testsuite/g++.dg/template/crash71.C
b/gcc/testsuite/g++.dg/template/crash71.C
index 3ac862ed81b..949f46eaf0d 100644
--- a/gcc/testsuite/g++.dg/template/crash71.C
+++ b/gcc/testsuite/g++.dg/template/crash71.C
@@ -1,3 +1,5 @@
// PR c++/30659
-extern "C" template A<char> foo(); // { dg-error "forbids|static
data|expected|template" }
+extern "C" template A<char> foo();
+// { dg-error "forbids|static data|expected|template" "" { target c++17_down }
.-1 }
+// { dg-error "permitted|forbids|static data|expected|template" "" { target
c++20 } .-2 }
