[C++ PATCH] Don't incorrectly reject {un,}signed char constexpr array initialization in templates (PR c++/87476)

[Jakub Jelinek]

Hi!

The following two testcases, one is a regression from GCC 8 (introduced by
the constructor to STRING_CST optimization), the other seems to fail since
C++11 support has been introduced (but is accepted by clang++) fail,
because during parsing with processing_template_decl we end up with creating
a STRING_CST with type of {un,}signed char array and later during
instantiation digest_init_r rejects it, because it already has such a type
rather than what it expects (char array) and bogusly complains that it is a
wide string.

The following patch fixes that.

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

2018-11-16  Jakub Jelinek  <ja...@redhat.com>

        PR c++/87476
        * typeck2.c (digest_init_r): Re-add handing of signed/unsigned char
        strings and add it to the initialization of wide array from non-wide
        string diagnostics too.

        * g++.dg/cpp0x/pr87476-1.C: New test.
        * g++.dg/cpp0x/pr87476-2.C: New test.

--- gcc/cp/typeck2.c.jj 2018-09-25 15:14:43.961258143 +0200
+++ gcc/cp/typeck2.c    2018-11-15 22:04:46.723230224 +0100
@@ -1063,7 +1063,9 @@ digest_init_r (tree type, tree init, int
 
          if (TYPE_PRECISION (typ1) == BITS_PER_UNIT)
            {
-             if (char_type != char_type_node)
+             if (char_type != char_type_node
+                 && char_type != signed_char_type_node
+                 && char_type != unsigned_char_type_node)
                {
                  if (complain & tf_error)
                    error_at (loc, "char-array initialized from wide string");
@@ -1072,7 +1074,9 @@ digest_init_r (tree type, tree init, int
            }
          else
            {
-             if (char_type == char_type_node)
+             if (char_type == char_type_node
+                 || char_type == signed_char_type_node
+                 || char_type == unsigned_char_type_node)
                {
                  if (complain & tf_error)
                    error_at (loc,
--- gcc/testsuite/g++.dg/cpp0x/pr87476-1.C.jj   2018-11-15 17:52:13.736758511 
+0100
+++ gcc/testsuite/g++.dg/cpp0x/pr87476-1.C      2018-11-15 17:42:03.577770280 
+0100
@@ -0,0 +1,13 @@
+// PR c++/87476
+// { dg-do compile { target c++11 } }
+
+template <int>
+struct S {
+  void operator () () { constexpr unsigned char p[1] {}; }
+};
+
+void
+foo ()
+{
+  S<0>{} ();
+}
--- gcc/testsuite/g++.dg/cpp0x/pr87476-2.C.jj   2018-11-15 22:06:27.615571180 
+0100
+++ gcc/testsuite/g++.dg/cpp0x/pr87476-2.C      2018-11-15 22:06:36.768420670 
+0100
@@ -0,0 +1,23 @@
+// PR c++/87476
+// { dg-do compile { target c++11 } }
+
+void f0 () { constexpr char p[] = "11111"; }
+void f1 () { constexpr unsigned char p[] = "11111"; }
+void f2 () { constexpr signed char p[] = "11111"; }
+template <int N>
+void f3 () { constexpr char p[] = "11111"; }
+template <int N>
+void f4 () { constexpr unsigned char p[] = "11111"; }
+template <int N>
+void f5 () { constexpr signed char p[] = "11111"; }
+
+void
+baz ()
+{
+  f0 ();
+  f1 ();
+  f2 ();
+  f3<0> ();
+  f4<0> ();
+  f5<0> ();
+}

        Jakub