Hi,
This is a v2 patch addressing feedback for:
https://gcc.gnu.org/pipermail/gcc-patches/2023-June/621050.html
macOS SDK headers using the CF_ENUM macro can expand to invalid C++ code
of the form:
typedef enum T : BaseType T;
i.e. an elaborated-type-specifier with an additional enum-base.
Upstream LLVM can be made to accept the above construct with
-Wno-error=elaborated-enum-base.
This patch adds the -Welaborated-enum-base warning to GCC and adjusts
the C++ parser to emit this warning instead of rejecting this code
outright.
The macro expansion in the macOS headers occurs in the case that the
compiler declares support for enums with underlying type using
__has_feature, see
https://gcc.gnu.org/pipermail/gcc-patches/2023-May/618450.html
GCC rejecting this construct outright means that GCC fails to bootstrap
on Darwin in the case that it (correctly) implements __has_feature and
declares support for C++ enums with underlying type.
With this patch, GCC can bootstrap on Darwin in combination with the
(WIP) __has_feature patch posted at:
https://gcc.gnu.org/pipermail/gcc-patches/2023-May/617878.html
Bootstrapped/regtested on aarch64-linux-gnu and x86_64-apple-darwin.
OK for trunk?
Thanks,
Alex
gcc/c-family/ChangeLog:
* c.opt (Welaborated-enum-base): New.
gcc/cp/ChangeLog:
* parser.cc (cp_parser_enum_specifier): Don't reject
elaborated-type-specifier with enum-base, instead emit new
Welaborated-enum-base warning.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/enum40.C: Adjust expected diagnostics.
* g++.dg/cpp0x/forw_enum6.C: Likewise.
* g++.dg/cpp0x/elab-enum-base.C: New test.
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index cead1995561..f935665d629 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -1488,6 +1488,13 @@ Wsubobject-linkage
C++ ObjC++ Var(warn_subobject_linkage) Warning Init(1)
Warn if a class type has a base or a field whose type uses the anonymous
namespace or depends on a type with no linkage.
+Welaborated-enum-base
+C++ ObjC++ Var(warn_elaborated_enum_base) Warning Init(1)
+Warn if an additional enum-base is used in an elaborated-type-specifier.
+That is, if an enum with given underlying type and no enumerator list
+is used in a declaration other than just a standalone declaration of the
+enum.
+
Wduplicate-decl-specifier
C ObjC Var(warn_duplicate_decl_specifier) Warning LangEnabledBy(C ObjC,Wall)
Warn when a declaration has duplicate const, volatile, restrict or _Atomic
specifier.
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index d77fbd20e56..4dd290717de 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -21024,11 +21024,13 @@ cp_parser_enum_specifier (cp_parser* parser)
/* Check for the `:' that denotes a specified underlying type in C++0x.
Note that a ':' could also indicate a bitfield width, however. */
+ location_t colon_loc = UNKNOWN_LOCATION;
if (cp_lexer_next_token_is (parser->lexer, CPP_COLON))
{
cp_decl_specifier_seq type_specifiers;
/* Consume the `:'. */
+ colon_loc = cp_lexer_peek_token (parser->lexer)->location;
cp_lexer_consume_token (parser->lexer);
auto tdf
@@ -21077,10 +21079,13 @@ cp_parser_enum_specifier (cp_parser* parser)
&& cp_lexer_next_token_is_not (parser->lexer, CPP_SEMICOLON))
{
if (has_underlying_type)
- cp_parser_commit_to_tentative_parse (parser);
- cp_parser_error (parser, "expected %<;%> or %<{%>");
- if (has_underlying_type)
- return error_mark_node;
+ pedwarn (colon_loc,
+ OPT_Welaborated_enum_base,
+ "declaration of enumeration with "
+ "fixed underlying type and no enumerator list is "
+ "only permitted as a standalone declaration");
+ else
+ cp_parser_error (parser, "expected %<;%> or %<{%>");
}
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/elab-enum-base.C
b/gcc/testsuite/g++.dg/cpp0x/elab-enum-base.C
new file mode 100644
index 00000000000..57141f013bd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/elab-enum-base.C
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+// Empty dg-options to override -pedantic-errors.
+
+typedef long CFIndex;
+typedef enum CFComparisonResult : CFIndex CFComparisonResult;
+// { dg-warning "declaration of enumeration with fixed underlying type" "" {
target *-*-* } .-1 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/enum40.C
b/gcc/testsuite/g++.dg/cpp0x/enum40.C
index cfdf2a4a18a..d3ffeb62d70 100644
--- a/gcc/testsuite/g++.dg/cpp0x/enum40.C
+++ b/gcc/testsuite/g++.dg/cpp0x/enum40.C
@@ -4,23 +4,25 @@
void
foo ()
{
- enum : int a alignas; // { dg-error "expected" }
+ enum : int a alignas; // { dg-error "declaration of enum" }
+ // { dg-error {expected '\(' before ';'} "" { target *-*-* } .-1 }
}
void
bar ()
{
- enum : int a; // { dg-error "expected" }
+ enum : int a; // { dg-error "declaration of enum" }
}
void
baz ()
{
- enum class a : int b alignas; // { dg-error "expected" }
+ enum class a : int b alignas; // { dg-error "declaration of enum" }
+ // { dg-error {expected '\(' before ';'} "" { target *-*-* } .-1 }
}
void
qux ()
{
- enum class a : int b; // { dg-error "expected" }
+ enum class a : int b; // { dg-error "declaration of enum" }
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/forw_enum6.C
b/gcc/testsuite/g++.dg/cpp0x/forw_enum6.C
index 01bf563bcdd..8ad3f733292 100644
--- a/gcc/testsuite/g++.dg/cpp0x/forw_enum6.C
+++ b/gcc/testsuite/g++.dg/cpp0x/forw_enum6.C
@@ -23,7 +23,7 @@ enum class E7 : int; //ok
enum class E3 e3; // { dg-error "scoped enum must not use" }
enum struct E3 e4; // { dg-error "scoped enum must not use" }
-enum E5 : int e5; // { dg-error "expected|invalid type" }
+enum E5 : int e5; // { dg-error "declaration of enumeration with fixed
underlying type|invalid type" }
enum E6 : int { a, b, c }; // { dg-message "previous definition" }
enum E6 : int { a, b, c }; // { dg-error "multiple definition" }
