c++: P2513R4, char8_t Compatibility and Portability Fix [PR106656]

P0482R6, which added char8_t, didn't allow

  const char arr[] = u8"howdy";

because it said "Declarations of arrays of char may currently be initialized
with UTF-8 string literals. Under this proposal, such initializations would
become ill-formed."  This caused too many issues, so P2513R4 alleviates some
of those compatibility problems.  In particular, "Arrays of char or unsigned
char may now be initialized with a UTF-8 string literal."  This restriction
has been lifted for initialization only, not implicit conversions.  Also,
my reading is that 'signed char' was excluded from the allowable conversions.

This is supposed to be treated as a DR in C++20.

	PR c++/106656

gcc/c-family/ChangeLog:

	* c-cppbuiltin.cc (c_cpp_builtins): Update value of __cpp_char8_t
	for C++20.

gcc/cp/ChangeLog:

	* typeck2.cc (array_string_literal_compatible_p): Allow
	initializing arrays of char or unsigned char by a UTF-8 string literal.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/feat-cxx2b.C: Adjust.
	* g++.dg/cpp2a/feat-cxx2a.C: Likewise.
	* g++.dg/ext/char8_t-feature-test-macro-2.C: Likewise.
	* g++.dg/ext/char8_t-init-2.C: Likewise.
	* g++.dg/cpp2a/char8_t3.C: New test.
	* g++.dg/cpp2a/char8_t4.C: New test.

diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc
index a1557eb23d5886b8f8612a7883bdb2e2a2ea4c18..b709f845c81310729b0eaa7120b4ec6505b24d40 100644 (file)
--- a/gcc/c-family/c-cppbuiltin.cc
+++ b/gcc/c-family/c-cppbuiltin.cc
@@ -1112,7 +1112,7 @@ c_cpp_builtins (cpp_reader *pfile)
       if (flag_threadsafe_statics)
        cpp_define (pfile, "__cpp_threadsafe_static_init=200806L");
       if (flag_char8_t)
-        cpp_define (pfile, "__cpp_char8_t=201811L");
+       cpp_define (pfile, "__cpp_char8_t=202207L");
 #ifndef THREAD_MODEL_SPEC
       /* Targets that define THREAD_MODEL_SPEC need to define
         __STDCPP_THREADS__ in their config/XXX/XXX-c.c themselves.  */

diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 75fd0e2a9bf80165300d1bd71e570951cc109922..739097a97342e5ad25e9579d79b7eef93cf84767 100644 (file)
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -1118,6 +1118,15 @@ array_string_literal_compatible_p (tree type, tree init)
   if (ordinary_char_type_p (to_char_type)
       && ordinary_char_type_p (from_char_type))
     return true;
+
+  /* P2513 (C++20/C++23): "an array of char or unsigned char may
+     be initialized by a UTF-8 string literal, or by such a string
+     literal enclosed in braces."  */
+  if (from_char_type == char8_type_node
+      && (to_char_type == char_type_node
+         || to_char_type == unsigned_char_type_node))
+    return true;
+
   return false;
 }
 

diff --git a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
index d3e40724085a672d9d870a7809368a3f408524a0..0537e1d24b5569812618e365d0c3dc73530718a7 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
+++ b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
@@ -504,8 +504,8 @@
 
 #ifndef __cpp_char8_t
 #  error "__cpp_char8_t"
-#elif __cpp_char8_t != 201811
-#  error "__cpp_char8_t != 201811"
+#elif __cpp_char8_t != 202207
+#  error "__cpp_char8_t != 202207"
 #endif
 
 #ifndef __cpp_designated_initializers

diff --git a/gcc/testsuite/g++.dg/cpp2a/char8_t3.C b/gcc/testsuite/g++.dg/cpp2a/char8_t3.C
new file mode 100644 (file)
index 0000000..071a718
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/char8_t3.C
@@ -0,0 +1,37 @@
+// PR c++/106656 - P2513 - char8_t Compatibility and Portability Fixes
+// { dg-do compile { target c++20 } }
+
+const char *p1 = u8""; // { dg-error "invalid conversion" }
+const unsigned char *p2 = u8""; // { dg-error "invalid conversion" }
+const signed char *p3 = u8""; // { dg-error "invalid conversion" }
+const char *p4 = { u8"" }; // { dg-error "invalid conversion" }
+const unsigned char *p5 = { u8"" }; // { dg-error "invalid conversion" }
+const signed char *p6 = { u8"" }; // { dg-error "invalid conversion" }
+const char *p7 = static_cast<const char *>(u8""); // { dg-error "invalid" }
+const char a1[] = u8"text";
+const unsigned char a2[] = u8"";
+const signed char a3[] = u8""; // { dg-error "cannot initialize array" }
+const char a4[] = { u8"text" };
+const unsigned char a5[] = { u8"" };
+const signed char a6[] = { u8"" }; // { dg-error "cannot initialize array" }
+
+const char *
+resource_id ()
+{
+  static const char res_id[] = u8"";
+  return res_id;
+}
+
+const char8_t x[] = "fail"; // { dg-error "cannot initialize array" }
+
+void fn (const char a[]);
+void
+g ()
+{
+  fn (u8"z"); // { dg-error "invalid conversion" }
+}
+
+char c = u8'c';
+unsigned char uc = u8'c';
+signed char sc = u8'c';
+char8_t c8 = 'c';

diff --git a/gcc/testsuite/g++.dg/cpp2a/char8_t4.C b/gcc/testsuite/g++.dg/cpp2a/char8_t4.C
new file mode 100644 (file)
index 0000000..c18081b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/char8_t4.C
@@ -0,0 +1,17 @@
+// PR c++/106656 - P2513 - char8_t Compatibility and Portability Fixes
+// { dg-do compile { target c++20 } }
+// [diff.cpp20.dcl]
+
+struct A {
+       char8_t s[10];
+};
+struct B {
+       char s[10];
+};
+
+void f(A);
+void f(B);
+
+int main() {
+       f({u8""}); // { dg-error "ambiguous" }
+}

diff --git a/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C b/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
index c65ea6bf48a83e502c64618384b72fa14c6ec304..02f3a377fd024e899e20a67dcd6ae7c82d9190ec 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
+++ b/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
@@ -504,8 +504,8 @@
 
 #ifndef __cpp_char8_t
 #  error "__cpp_char8_t"
-#elif __cpp_char8_t != 201811
-#  error "__cpp_char8_t != 201811"
+#elif __cpp_char8_t != 202207
+#  error "__cpp_char8_t != 202207"
 #endif
 
 #ifndef __cpp_designated_initializers

diff --git a/gcc/testsuite/g++.dg/ext/char8_t-feature-test-macro-2.C b/gcc/testsuite/g++.dg/ext/char8_t-feature-test-macro-2.C
index df1063f6aa185c8aecf0fb49b5f17f00e8e6e8a5..2d0f9045acfcc0145fbf2be01b90882240027ec3 100644 (file)
--- a/gcc/testsuite/g++.dg/ext/char8_t-feature-test-macro-2.C
+++ b/gcc/testsuite/g++.dg/ext/char8_t-feature-test-macro-2.C
@@ -5,6 +5,6 @@
 
 #if !defined(__cpp_char8_t)
 #  error __cpp_char8_t is not defined!
-#elif __cpp_char8_t != 201811
-#  error __cpp_char8_t != 201811
+#elif __cpp_char8_t != 202207
+#  error __cpp_char8_t != 202207
 #endif

diff --git a/gcc/testsuite/g++.dg/ext/char8_t-init-2.C b/gcc/testsuite/g++.dg/ext/char8_t-init-2.C
index c713bc122663ea20b58618309d63a55b849776fa..02a96ffe5a492448d70bb24c9757f038da2ecf65 100644 (file)
--- a/gcc/testsuite/g++.dg/ext/char8_t-init-2.C
+++ b/gcc/testsuite/g++.dg/ext/char8_t-init-2.C
@@ -21,7 +21,7 @@ const char8_t (&rca4)[2] = u8"x";
 const char8_t (&rca5)[2] = u"x"; // { dg-error "invalid initialization of reference of type .const char8_t ....... from expression of type .const char16_t ...." "char8_t" }
 
 char ca1[] = "x";
-char ca2[] = u8"x"; // { dg-error "from a string literal with type array of .char8_t." "char8_t" }
+char ca2[] = u8"x";
 char8_t ca3[] = "x"; // { dg-error "from a string literal with type array of .char." "char8_t" }
 char8_t ca4[] = u8"x";
 char8_t ca5[] = u"x"; // { dg-error "from a string literal with type array of .char16_t." "char8_t" }
@@ -30,4 +30,4 @@ signed char sca1[] = "x";
 signed char sca2[] = u8"x"; // { dg-error "from a string literal with type array of .char8_t." "char8_t" }
 
 unsigned char uca1[] = "x";
-unsigned char uca2[] = u8"x"; // { dg-error "from a string literal with type array of .char8_t." "char8_t" }
+unsigned char uca2[] = u8"x";