[gcc r14-10100] c++: Fix ICE with xobj parms and maybe incomplete decl-specifiers

[Nathaniel Shead <nshead@gcc.gnu.org>]

https://gcc.gnu.org/g:7318f1a389769ab540f414fcba743e90051d466b

commit r14-10100-g7318f1a389769ab540f414fcba743e90051d466b
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Sat Apr 20 14:44:11 2024 +1000

    c++: Fix ICE with xobj parms and maybe incomplete decl-specifiers
    
    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>

Diff:
---
 gcc/cp/parser.cc                                 | 5 +++--
 gcc/testsuite/g++.dg/cpp23/explicit-obj-basic7.C | 9 +++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index c23758cf5cf..598380dda08 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);
+};