From: Marek Polacek <polacek@redhat.com>
Date: Fri, 31 Jan 2025 19:52:36 +0000 (-0500)
Subject: c++: bogus -Wvexing-parse with trailing-return-type [PR118718]
X-Git-Tag: basepoints/gcc-16~2199
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=53d1f6cdb5a82e859176e854636400faba0bf0bf;p=thirdparty%2Fgcc.git

c++: bogus -Wvexing-parse with trailing-return-type [PR118718]

This warning should not warn for

  auto f1 () -> auto;

because that cannot be confused with initializing a variable.

	PR c++/118718

gcc/cp/ChangeLog:

	* parser.cc (warn_about_ambiguous_parse): Don't warn when a trailing
	return type is present.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wvexing-parse10.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 44515bb9074..1da881e295b 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -23617,6 +23617,10 @@ warn_about_ambiguous_parse (const cp_decl_specifier_seq *decl_specifiers,
 			(const_cast<cp_declarator *>(declarator))))
     return;
 
+  /* Don't warn for auto f () -> auto.  */
+  if (declarator->u.function.late_return_type)
+    return;
+
   /* Don't warn when the whole declarator (not just the declarator-id!)
      was parenthesized.  That is, don't warn for int(n()) but do warn
      for int(f)().  */
diff --git a/gcc/testsuite/g++.dg/warn/Wvexing-parse10.C b/gcc/testsuite/g++.dg/warn/Wvexing-parse10.C
new file mode 100644
index 00000000000..3fbe88b7d00
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wvexing-parse10.C
@@ -0,0 +1,9 @@
+// PR c++/118718
+// { dg-do compile { target c++14 } }
+
+void
+fn ()
+{
+  auto f1 () -> auto;
+  auto f2 (); // { dg-warning "empty parentheses" }
+}