[PATCH] c++: Fix ICE with xobj parms and maybe incomplete decl-specifiers

[Nathaniel Shead <nathanieloshead@gmail.com>]

Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?

-- >8 --

This fixes a null dereference issue when decl_specifiers.type is not yet
provided.

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_parameter_declaration): Check if
	decl_specifiers.type is null.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/explicit-obj-basic7.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/parser.cc                                 | 5 +++--
 gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C | 9 +++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 50d3ad35b61..97ee2650dc4 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -25780,8 +25780,9 @@ cp_parser_parameter_declaration (cp_parser *parser,
     }
 
   if (xobj_param_p
-      && (declarator ? declarator->parameter_pack_p
-		     : PACK_EXPANSION_P (decl_specifiers.type)))
+      && ((declarator && declarator->parameter_pack_p)
+	  || (decl_specifiers.type
+	      && PACK_EXPANSION_P (decl_specifiers.type))))
     {
       location_t xobj_param
 	= make_location (decl_specifiers.locations[ds_this],
diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C
new file mode 100644
index 00000000000..a474e97fc18
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C
@@ -0,0 +1,9 @@
+// { dg-do compile { target c++23 } }
+
+// Shouldn't ICE
+struct S {
+  void a(this long);
+  void b(this const long);
+  void c(this long unsigned);
+  void c(this signed);
+};
-- 
2.43.2