[PATCH] c++: Make *_cast<*> parsing more robust to errors [PR108438]

[Simon Martin]

We ICE upon the following when trying to emit a -Wlogical-not-parentheses
warning:

=== cut here ===
template <typename T> T foo (T arg, T& ref, T* ptr) {
  int a = 1;
  return static_cast<T!>(a);
}
=== cut here ===

This patch makes *_cast<*> parsing more robust by skipping to the closing '>'
upon error in the target type.

Successfully tested on x86_64-pc-linux-gnu.

(Note that I have a patch pending review that also adds g++.dg/parse/crash74.C;
I will obviously handle the name conflict at commit time)

        PR c++/108438

gcc/cp/ChangeLog:

        * parser.cc (cp_parser_postfix_expression): Skip to the closing '>'
        upon error parsing the target type of *_cast<*> expressions.

gcc/testsuite/ChangeLog:

        * g++.dg/parse/crash74.C: New test.

---
 gcc/cp/parser.cc                     | 3 ++-
 gcc/testsuite/g++.dg/parse/crash74.C | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/parse/crash74.C

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index bc4a2359153..3516c2aa38b 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -7569,7 +7569,8 @@ cp_parser_postfix_expression (cp_parser *parser, bool 
address_p, bool cast_p,
                                  NULL);
        parser->in_type_id_in_expr_p = saved_in_type_id_in_expr_p;
        /* Look for the closing `>'.  */
-       cp_parser_require (parser, CPP_GREATER, RT_GREATER);
+       if (!cp_parser_require (parser, CPP_GREATER, RT_GREATER))
+         cp_parser_skip_to_end_of_template_parameter_list (parser);
        /* Restore the old message.  */
        parser->type_definition_forbidden_message = saved_message;
 
diff --git a/gcc/testsuite/g++.dg/parse/crash74.C 
b/gcc/testsuite/g++.dg/parse/crash74.C
new file mode 100644
index 00000000000..81a16e35b14
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/crash74.C
@@ -0,0 +1,9 @@
+// PR c++/108438
+// { dg-options "-Wlogical-not-parentheses" }
+
+template <typename T>
+T foo (T arg, T& ref, T* ptr)
+{
+  int a = 1;
+  return static_cast<T!>(a); // { dg-error "expected" }
+}
-- 
2.44.0