On Wed, May 06, 2026 at 04:15:03PM -0400, Jason Merrill wrote:
On 5/5/26 9:19 PM, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
Additionally tested with the "Optimization only" checks disabled
to see if it isn't hiding any errors.
-- >8 --
In
void fn (int i = sizeof (i)) {}
the i in sizeof should refer to the parameter ([basic.scope.pdecl]) and
since the second i is not evaluated, the code is valid per
[dcl.fct.default]/9: A parameter shall not appear as a potentially
evaluated expression in a default argument.
To make this work, we have to defer parsing of the default argument
until we've done grokdeclarator + pushdecl on i.
How about doing that by moving grokdeclarator/pushdecl into
cp_parser_parameter_declaration rather than mess with DEFERRED_PARSE?
Looks like I actually can do that. I just have to pass the decl back
to _parameter_declaration_list, otherwise the pending_decls handling
could become ugly. But it seems better than the DEFERRED_PARSE
approach.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
In
void fn (int i = sizeof (i)) {}
the i in sizeof should refer to the parameter ([basic.scope.pdecl]) and
since the second i is not evaluated, the code is valid per
[dcl.fct.default]/9: A parameter shall not appear as a potentially
evaluated expression in a default argument.
This patch fixes this by moving the grokdeclarator call from
_parameter_declaration_list to _parameter_declaration and maybe calling
pushdecl before parsing the default argument.
PR c++/50479
PR c++/62244
gcc/cp/ChangeLog:
* parser.cc (cp_parser_parameter_declaration_list): Move the
grokdeclarator call and setting DECL_SOURCE_LOCATION to...
(cp_parser_parameter_declaration): ...here. New tree parameter.
Set it. Call pushdecl for a named decl with a default argument.
gcc/testsuite/ChangeLog:
* g++.dg/reflect/parm1.C: Uncomment code.
* g++.dg/parse/defarg22.C: New test.
* g++.dg/parse/defarg23.C: New test.
* g++.dg/parse/defarg24.C: New test.
* g++.dg/parse/defarg25.C: New test.
* g++.dg/parse/defarg26.C: New test.
---
gcc/cp/parser.cc | 63 +++++++++++++++++----------
gcc/testsuite/g++.dg/parse/defarg22.C | 16 +++++++
gcc/testsuite/g++.dg/parse/defarg23.C | 36 +++++++++++++++
gcc/testsuite/g++.dg/parse/defarg24.C | 12 +++++
gcc/testsuite/g++.dg/parse/defarg25.C | 22 ++++++++++
gcc/testsuite/g++.dg/parse/defarg26.C | 18 ++++++++
gcc/testsuite/g++.dg/reflect/parm1.C | 5 +--
7 files changed, 146 insertions(+), 26 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/parse/defarg22.C
create mode 100644 gcc/testsuite/g++.dg/parse/defarg23.C
create mode 100644 gcc/testsuite/g++.dg/parse/defarg24.C
create mode 100644 gcc/testsuite/g++.dg/parse/defarg25.C
create mode 100644 gcc/testsuite/g++.dg/parse/defarg26.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index d128de771b5..66126115e61 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -2785,7 +2785,7 @@ static tree cp_parser_parameter_declaration_clause
static tree cp_parser_parameter_declaration_list
(cp_parser *, cp_parser_flags, auto_vec<tree> *);
static cp_parameter_declarator *cp_parser_parameter_declaration
- (cp_parser *, cp_parser_flags, bool, bool *);
+ (cp_parser *, cp_parser_flags, bool, bool *, tree * = nullptr);
static tree cp_parser_default_argument
(cp_parser *, bool);
static void cp_parser_function_body
@@ -28301,24 +28301,7 @@ cp_parser_parameter_declaration_list (cp_parser*
parser,
parameter
= cp_parser_parameter_declaration (parser, flags,
/*template_parm_p=*/false,
- &parenthesized_p);
-
- /* We don't know yet if the enclosing context is unavailable or
deprecated,
- so wait and deal with it in grokparms if appropriate. */
- deprecated_state = UNAVAILABLE_DEPRECATED_SUPPRESS;
-
- if (parameter && !cp_parser_error_occurred (parser))
- {
- decl = grokdeclarator (parameter->declarator,
- ¶meter->decl_specifiers,
- PARM,
- parameter->default_argument != NULL_TREE,
- ¶meter->decl_specifiers.attributes);
- if (decl != error_mark_node && parameter->loc != UNKNOWN_LOCATION)
- DECL_SOURCE_LOCATION (decl) = parameter->loc;
- }
-
- deprecated_state = DEPRECATED_NORMAL;
+ &parenthesized_p, &decl);
/* If a parse error occurred parsing the parameter declaration,
then the entire parameter-declaration-list is erroneous. */
@@ -28361,7 +28344,10 @@ cp_parser_parameter_declaration_list (cp_parser*
parser,
return false;
}())
pending_decls->safe_push (decl);
- else
+ /* If we saw a default argument, we've already pushed this decl.
+ (An ill-formed default argument should have been parsed to
+ error_mark_node.) */
+ else if (!parameter->default_argument)
decl = pushdecl (decl);
}
@@ -28474,6 +28460,9 @@ cp_parser_parameter_declaration_list (cp_parser* parser,
token encountered during the parsing of the assignment-expression
is not interpreted as a greater-than operator.)
+ If DECL is non-null, we are called from cp_parser_parameter_declaration_list
+ and will perform grokdeclarator here; DECL will be set to the result.
