[gcc r14-6342] c++: undiagnosed error_mark_node from cp_build_c_cast [PR112658]

[Patrick Palka]

https://gcc.gnu.org/g:5764825aed613f201a8bc47e5b239027a39691f0

commit r14-6342-g5764825aed613f201a8bc47e5b239027a39691f0
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Dec 8 13:33:55 2023 -0500

    c++: undiagnosed error_mark_node from cp_build_c_cast [PR112658]
    
    When cp_build_c_cast commits to an erroneous const_cast, we neglect to
    replay errors from build_const_cast_1 which can lead to us incorrectly
    accepting (and "miscompiling") the cast, or triggering the assert in
    finish_expr_stmt.
    
    This patch fixes this oversight.  This was the original fix for the ICE
    in PR112658 before r14-5941-g305a2686c99bf9 made us accept the testcase
    there after all.  I wasn't able to come up with an alternate testcase for
    which this fix has an effect anymore, but below is a reduced version of
    the PR112658 testcase (accepted ever since r14-5941) for good measure.
    
            PR c++/112658
            PR c++/94264
    
    gcc/cp/ChangeLog:
    
            * typeck.cc (cp_build_c_cast): If we're committed to a const_cast
            and the result is erroneous, call build_const_cast_1 a second
            time to issue errors.  Use complain=tf_none instead of =false.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp0x/initlist-array20.C: New test.

Diff:
---
 gcc/cp/typeck.cc                              |  4 +++-
 gcc/testsuite/g++.dg/cpp0x/initlist-array20.C | 11 +++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 8e4cfae08aa..258cfd43114 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -9213,6 +9213,8 @@ cp_build_c_cast (location_t loc, tree type, tree expr,
 	  maybe_warn_about_useless_cast (loc, type, value, complain);
 	  maybe_warn_about_cast_ignoring_quals (loc, type, complain);
 	}
+      else if (complain & tf_error)
+	build_const_cast_1 (loc, type, value, tf_error, &valid_p);
       return result;
     }
 
@@ -9248,7 +9250,7 @@ cp_build_c_cast (location_t loc, tree type, tree expr,
 	 to succeed.  */
       if (!same_type_p (non_reference (type), non_reference (result_type)))
 	{
-	  result = build_const_cast_1 (loc, type, result, false, &valid_p);
+	  result = build_const_cast_1 (loc, type, result, tf_none, &valid_p);
 	  gcc_assert (valid_p);
 	}
       return result;
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-array20.C b/gcc/testsuite/g++.dg/cpp0x/initlist-array20.C
new file mode 100644
index 00000000000..048c5b45652
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-array20.C
@@ -0,0 +1,11 @@
+// PR c++/112658
+// PR c++/94264
+// { dg-do compile { target c++11 } }
+
+void f(int*);
+
+int main() {
+  using array = int[];
+  f(array{42});
+  f((int*)array{42});
+}