[PATCH] testsuite: Add testcase from C++23 P2314R4 - Character sets and encodings

[Jakub Jelinek <jakub@redhat.com>]

Hi!

I've read the paper and I believe we just implement it with no changes
needed (at least since PR67224 and similar libcpp changes in GCC 10),
but I could be wrong.

The following patch at least adds a testcase from the start of the paper.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Do you agree that we can mark the paper as implemented or do you think
we need to change something (what?)?

2022-11-04  Jakub Jelinek  <jakub@redhat.com>

	* g++.dg/cpp23/charset1.C: New testcase from C++23 P2314R4.

--- gcc/testsuite/g++.dg/cpp23/charset1.C.jj	2022-11-03 10:56:48.114588796 +0100
+++ gcc/testsuite/g++.dg/cpp23/charset1.C	2022-11-03 10:56:39.162711201 +0100
@@ -0,0 +1,10 @@
+// P2314R4
+// { dg-do compile { target c++23 } }
+// { dg-options "-finput-charset=UTF-8 -fexec-charset=UTF-8" }
+
+#define S(x) # x
+const char s1[] = S(Köppe);       // "Köppe"
+const char s2[] = S(K\u00f6ppe);  // "Köppe"
+
+static_assert (sizeof (s1) == 7);
+static_assert (sizeof (s2) == 7);

	Jakub