[clang][sema] Enable first-class bool support for C2x

Implement N2395 for C2x.

This also covers adding "bool", which is part of N2394.

Differential Revision: https://reviews.llvm.org/D120244

Author: tbaederr

clang/docs/ReleaseNotes.rst

@@ -110,6 +110,7 @@ C2x Feature Support
 -------------------
 
 - Implemented `WG14 N2674 The noreturn attribute <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2764.pdf>`_.
+- Implemented `WG14 N2935 Make false and true first-class language features <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2935.pdf>`_.
 
 C++ Language Changes in Clang
 -----------------------------

clang/lib/Frontend/CompilerInvocation.cpp

@@ -3249,8 +3249,8 @@ void CompilerInvocation::setLangDefaults(LangOptions &Opts, InputKind IK,
 
   Opts.RenderScript = IK.getLanguage() == Language::RenderScript;
 
-  // OpenCL and C++ both have bool, true, false keywords.
-  Opts.Bool = Opts.OpenCL || Opts.CPlusPlus;
+  // OpenCL, C++ and C2x have bool, true, false keywords.
+  Opts.Bool = Opts.OpenCL || Opts.CPlusPlus || Opts.C2x;
 
   // OpenCL has half keyword
   Opts.Half = Opts.OpenCL;

clang/lib/Headers/stdbool.h

@@ -10,8 +10,13 @@
 #ifndef __STDBOOL_H
 #define __STDBOOL_H
 
-/* Don't define bool, true, and false in C++, except as a GNU extension. */
-#ifndef __cplusplus
+#define __bool_true_false_are_defined 1
+
+#if __STDC_VERSION__ > 201710L
+#if !defined(_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS)
+#warning "the <stdbool.h> header is deprecated in C2x"
+#endif /* !defined(_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS) */
+#elif !defined(__cplusplus)
 #define bool _Bool
 #define true 1
 #define false 0
@@ -20,12 +25,10 @@
 #define _Bool bool
 #if __cplusplus < 201103L
 /* For C++98, define bool, false, true as a GNU extension. */
-#define bool  bool
+#define bool bool
 #define false false
-#define true  true
+#define true true
 #endif
 #endif
 
-#define __bool_true_false_are_defined 1
-
 #endif /* __STDBOOL_H */

clang/test/Headers/stdbool.c

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c11 -E -dM %s 2>&1 | FileCheck --check-prefix=CHECK-C11 %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c2x -E -dM %s 2>&1 | FileCheck --check-prefix=CHECK-C2X %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c2x -E -dM -D_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS %s 2>&1 | FileCheck --check-prefix=CHECK-C2X-CRT %s
+
+#include <stdbool.h>
+
+// CHECK-C11: #define bool _Bool
+// CHECK-C11: #define false 0
+// CHECK-C11: #define true 1
+
+// CHECK-C2X: warning "the <stdbool.h> header is deprecated
+// CHECK-C2X-NOT: #define bool
+// CHECK-C2X-NOT: #define true
+// CHECK-C2X-NOT: #define falsea
+
+// CHECK-C2X-CRT-NOT: warning "the <stdbool.h> header is deprecated
+// CHECK-C2X-CRT-NOT: #define bool
+// CHECK-C2X-CRT-NOT: #define true
+// CHECK-C2X-CRT-NOT: #define false

clang/test/Sema/c2x-bool.c

@@ -0,0 +1,41 @@
+// RUN: %clang_cc1 -std=c2x -fsyntax-only -verify %s
+
+_Static_assert(_Generic(true, _Bool : 1, default: 0));
+_Static_assert(_Generic(false, _Bool : 1, default: 0));
+
+_Static_assert(_Generic(true, bool : 1, default: 0));
+_Static_assert(_Generic(false, bool : 1, default: 0));
+
+_Static_assert(_Generic(true, bool : true, default: false));
+_Static_assert(_Generic(false, bool : true, default: false));
+
+_Static_assert(true == (bool)+1);
+_Static_assert(false == (bool)+0);
+
+_Static_assert(_Generic(+true, bool : 0, unsigned int : 0, signed int : 1, default : 0));
+
+struct S {
+  bool b : 1;
+} s;
+_Static_assert(_Generic(+s.b, bool : 0, unsigned int : 0, signed int : 1, default : 0));
+
+static void *f = false; // expected-warning {{to null from a constant boolean expression}}
+static int one = true;
+static int zero = false;
+
+static void do_work() {
+  char *str = "Foo";
+  str[false] = 'f';
+  str[true] = 'f';
+
+  char c1[true];
+  char c2[false];
+}
+
+#if true != 1
+#error true should be 1 in the preprocessor
+#endif
+
+#if false != 0
+#error false should be 0 in the preprocessor
+#endif