From: Marek Polacek <polacek@redhat.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>, Jason Merrill <jason@redhat.com>
Subject: [PATCH] c++: fix parsing with auto(x) at block scope [PR112482]
Date: Thu, 14 Dec 2023 16:02:27 -0500 [thread overview]
Message-ID: <20231214210227.1190177-1-polacek@redhat.com> (raw)
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
This is sort of like r14-5514, but at block scope. Consider
struct A { A(int, int); };
void
g (int a)
{
A bar(auto(a), 42); // not a fn decl
}
where we emit error: 'auto' parameter not permitted in this context
which is bogus -- bar doesn't declare a function, so the auto is OK,
but we don't know it till we've seen the second argument. The error
comes from grokdeclarator invoked just after we've parsed the auto(a).
A possible approach seems to be to delay the auto parameter checking
and only check once we know we are indeed dealing with a function
declaration. For tparms, we should still emit the error right away.
PR c++/112482
gcc/cp/ChangeLog:
* decl.cc (grokdeclarator): Do not issue the auto parameter error while
tentatively parsing a function parameter.
* parser.cc (cp_parser_parameter_declaration_clause): Check it here.
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/auto-fncast15.C: New test.
---
gcc/cp/decl.cc | 13 +++++++++++--
gcc/cp/parser.cc | 17 +++++++++++++++--
gcc/testsuite/g++.dg/cpp23/auto-fncast15.C | 21 +++++++++++++++++++++
3 files changed, 47 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast15.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 4d17ead123a..1ffe4c82748 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14203,6 +14203,7 @@ grokdeclarator (const cp_declarator *declarator,
tree auto_node = type_uses_auto (type);
if (auto_node && !(cxx_dialect >= cxx17 && template_parm_flag))
{
+ bool err_p = true;
if (cxx_dialect >= cxx14)
{
if (decl_context == PARM && AUTO_IS_DECLTYPE (auto_node))
@@ -14221,13 +14222,21 @@ grokdeclarator (const cp_declarator *declarator,
"abbreviated function template");
inform (DECL_SOURCE_LOCATION (c), "%qD declared here", c);
}
- else
+ else if (decl_context == CATCHPARM || template_parm_flag)
error_at (typespec_loc,
"%<auto%> parameter not permitted in this context");
+ else
+ /* Do not issue an error while tentatively parsing a function
+ parameter: for T t(auto(a), 42);, when we just saw the 1st
+ parameter, we don't know yet that this construct won't be
+ a function declaration. Defer the checking to
+ cp_parser_parameter_declaration_clause. */
+ err_p = false;
}
else
error_at (typespec_loc, "parameter declared %<auto%>");
- type = error_mark_node;
+ if (err_p)
+ type = error_mark_node;
}
/* A parameter declared as an array of T is really a pointer to T.
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 58e910d64af..e4fbab1bab5 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -25102,8 +25102,21 @@ cp_parser_parameter_declaration_clause (cp_parser* parser,
committed yet, nor should we. Pushing here will detect the error
of redefining a parameter. */
if (cp_lexer_next_token_is (parser->lexer, CPP_CLOSE_PAREN))
- for (tree p : pending_decls)
- pushdecl (p);
+ {
+ for (tree p : pending_decls)
+ pushdecl (p);
+
+ /* Delayed checking of auto parameters. */
+ if (!parser->auto_is_implicit_function_template_parm_p
+ && cxx_dialect >= cxx14)
+ for (tree p = parameters; p; p = TREE_CHAIN (p))
+ if (type_uses_auto (TREE_TYPE (TREE_VALUE (p))))
+ {
+ error_at (location_of (TREE_VALUE (p)),
+ "%<auto%> parameter not permitted in this context");
+ TREE_TYPE (TREE_VALUE (p)) = error_mark_node;
+ }
+ }
/* Finish the parameter list. */
if (!ellipsis_p)
diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast15.C b/gcc/testsuite/g++.dg/cpp23/auto-fncast15.C
new file mode 100644
index 00000000000..deb1efcc46c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast15.C
@@ -0,0 +1,21 @@
+// PR c++/112482
+// { dg-do compile { target c++23 } }
+// { dg-options "-Wno-vexing-parse" }
+
+void foo (auto i, auto j);
+
+struct A {
+ A(int,int);
+};
+
+void
+g (int a)
+{
+ A b1(auto(42), auto(42));
+ A b2(auto(a), auto(42));
+ A b3(auto(42), auto(a));
+ A b4(auto(a), // { dg-error "13:'auto' parameter" }
+ auto(a2)); // { dg-error "13:'auto' parameter" }
+ int v1(auto(42));
+ int fn1(auto(a)); // { dg-error "16:'auto' parameter" }
+}
base-commit: 767e2674875139ac8f354ceee655c1a9561b9779
--
2.43.0
next reply other threads:[~2023-12-14 21:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 21:02 Marek Polacek [this message]
2023-12-14 21:07 ` Jason Merrill
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