Add C++26 compile flags.

Now that we've updated to C++23, we need to add C++26/C++2c command line
flags, as discussed in
https://discourse.llvm.org/t/rfc-lets-just-call-it-c-26-and-forget-about-the-c-2c-business-at-least-internally/70383

Differential Revision: https://reviews.llvm.org/D150450

diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index 6c59ffd2ab12068cbe476a776b94bde91653b396..faaf9c8d97ef3d203687a79246cc5a4af9363fae 100644 (file)
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -201,6 +201,14 @@ Language Selection and Mode Options
 
    ISO C++ 2023 with amendments and GNU extensions
 
+  | ``c++2c``
+
+   Working draft for C++2c
+
+  | ``gnu++2c``
+
+   Working draft for C++2c with GNU extensions
+
  The default C++ language standard is ``gnu++17``.
 
  Supported values for the OpenCL language are:

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 7e8dca8b31871f91396058e5d5f2d1201c33661c..9601849bd67d3abbad0753932cebf643c7c05f84 100644 (file)
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -109,6 +109,10 @@ C++23 Feature Support
   functions. Which include allowing non-literal types as return values and parameters, allow calling of
   non-constexpr functions and constructors.
 
+C++2c Feature Support
+^^^^^^^^^^^^^^^^^^^^^
+- Compiler flags ``-std=c++2c`` and ``-std=gnu++2c`` have been added for experimental C++2c implementation work.
+
 Resolutions to C++ Defect Reports
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Implemented `DR2397 <https://wg21.link/CWG2397>`_ which allows ``auto`` specifier for pointers

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 1a792f1cf6e8b29e14203da1e1094be0650714f6..08b8f02460c167ea7f69789f8455825a9ae21a86 100644 (file)
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -307,6 +307,11 @@ def : DiagGroup<"c++98-c++11-c++14-c++17-compat-pedantic",
 def CXXPre23Compat : DiagGroup<"pre-c++23-compat">;
 def CXXPre23CompatPedantic :
   DiagGroup<"pre-c++23-compat-pedantic", [CXXPre23Compat]>;
+def CXXPre26Compat : DiagGroup<"pre-c++26-compat">;
+def CXXPre26CompatPedantic :
+  DiagGroup<"pre-c++26-compat-pedantic", [CXXPre26Compat]>;
+def : DiagGroup<"pre-c++2c-compat", [CXXPre26Compat]>;
+def : DiagGroup<"pre-c++2c-compat-pedantic", [CXXPre26CompatPedantic]>;
 
 def CXX98CompatBindToTemporaryCopy :
   DiagGroup<"c++98-compat-bind-to-temporary-copy">;
@@ -1112,11 +1117,16 @@ def CXX20 : DiagGroup<"c++20-extensions", [CXX20Designator, CXX20Attrs]>;
 // earlier C++ versions.
 def CXX23 : DiagGroup<"c++23-extensions">;
 
+// A warning group for warnings about using C++26 features as extensions in
+// earlier C++ versions.
+def CXX26 : DiagGroup<"c++26-extensions">;
+
 def : DiagGroup<"c++0x-extensions", [CXX11]>;
 def : DiagGroup<"c++1y-extensions", [CXX14]>;
 def : DiagGroup<"c++1z-extensions", [CXX17]>;
 def : DiagGroup<"c++2a-extensions", [CXX20]>;
 def : DiagGroup<"c++2b-extensions", [CXX23]>;
+def : DiagGroup<"c++2c-extensions", [CXX26]>;
 
 def DelegatingCtorCycles :
   DiagGroup<"delegating-ctor-cycles">;

diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 495b17e769e5d92816e73d7f3f7e8042fae3be16..95cd6959cfb5236efe13d66fe47fb6cbd80c9916 100644 (file)
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -98,6 +98,7 @@ LANGOPT(CPlusPlus14       , 1, 0, "C++14")
 LANGOPT(CPlusPlus17       , 1, 0, "C++17")
 LANGOPT(CPlusPlus20       , 1, 0, "C++20")
 LANGOPT(CPlusPlus23       , 1, 0, "C++23")
+LANGOPT(CPlusPlus26       , 1, 0, "C++26")
 LANGOPT(ObjC              , 1, 0, "Objective-C")
 BENIGN_LANGOPT(ObjCDefaultSynthProperties , 1, 0,
                "Objective-C auto-synthesized properties")

diff --git a/clang/include/clang/Basic/LangStandard.h b/clang/include/clang/Basic/LangStandard.h
index ebe14c8a3f8fd4987e71ea60fd7a412038701c7a..fd949bcd68555c59b9bd211cb6219e124f57a5bd 100644 (file)
--- a/clang/include/clang/Basic/LangStandard.h
+++ b/clang/include/clang/Basic/LangStandard.h
@@ -56,11 +56,12 @@ enum LangFeatures {
   CPlusPlus17 = (1 << 8),
   CPlusPlus20 = (1 << 9),
   CPlusPlus23 = (1 << 10),
-  Digraphs = (1 << 11),
-  GNUMode = (1 << 12),
-  HexFloat = (1 << 13),
-  OpenCL = (1 << 14),
-  HLSL = (1 << 15)
+  CPlusPlus26 = (1 << 11),
+  Digraphs = (1 << 12),
+  GNUMode = (1 << 13),
+  HexFloat = (1 << 14),
+  OpenCL = (1 << 15),
+  HLSL = (1 << 16)
 };
 
 /// LangStandard - Information about the properties of a particular language
@@ -121,6 +122,9 @@ public:
   /// isCPlusPlus23 - Language is a post-C++23 variant (or later).
   bool isCPlusPlus23() const { return Flags & CPlusPlus23; }
 
+  /// isCPlusPlus26 - Language is a post-C++26 variant (or later).
+  bool isCPlusPlus26() const { return Flags & CPlusPlus26; }
+
   /// hasDigraphs - Language supports digraphs.
   bool hasDigraphs() const { return Flags & Digraphs; }
 

diff --git a/clang/include/clang/Basic/LangStandards.def b/clang/include/clang/Basic/LangStandards.def
index 8e4d3759f33b761604095f9cc3eb8140fa569bba..911b626e4c9661584b726030e90040b868111e97 100644 (file)
--- a/clang/include/clang/Basic/LangStandards.def
+++ b/clang/include/clang/Basic/LangStandards.def
@@ -163,6 +163,18 @@ LANGSTANDARD(gnucxx23, "gnu++23",
              CPlusPlus20 | CPlusPlus23 | Digraphs | HexFloat | GNUMode)
 LANGSTANDARD_ALIAS_DEPR(gnucxx23, "gnu++2b")
 
+LANGSTANDARD(cxx26, "c++2c",
+             CXX, "Working draft for C++2c",
+             LineComment | CPlusPlus | CPlusPlus11 | CPlusPlus14 | CPlusPlus17 |
+             CPlusPlus20 | CPlusPlus23 | CPlusPlus26 | Digraphs | HexFloat)
+LANGSTANDARD_ALIAS(cxx26, "c++26")
+
+LANGSTANDARD(gnucxx26, "gnu++2c",
+             CXX, "Working draft for C++2c with GNU extensions",
+             LineComment | CPlusPlus | CPlusPlus11 | CPlusPlus14 | CPlusPlus17 |
+             CPlusPlus20 | CPlusPlus23 | CPlusPlus26 | Digraphs | HexFloat | GNUMode)
+LANGSTANDARD_ALIAS(gnucxx26, "gnu++26")
+
 // OpenCL
 LANGSTANDARD(opencl10, "cl1.0",
              OpenCL, "OpenCL 1.0",

diff --git a/clang/lib/Basic/LangOptions.cpp b/clang/lib/Basic/LangOptions.cpp
index 1abbaa9e4b2b44da16d5eeaa976f8b3fd690da8c..b44c71f572bee6af9837c4f8284ea60aeabcc891 100644 (file)
--- a/clang/lib/Basic/LangOptions.cpp
+++ b/clang/lib/Basic/LangOptions.cpp
@@ -118,6 +118,7 @@ void LangOptions::setLangDefaults(LangOptions &Opts, Language Lang,
   Opts.CPlusPlus17 = Std.isCPlusPlus17();
   Opts.CPlusPlus20 = Std.isCPlusPlus20();
   Opts.CPlusPlus23 = Std.isCPlusPlus23();
+  Opts.CPlusPlus26 = Std.isCPlusPlus26();
   Opts.GNUMode = Std.isGNUMode();
   Opts.GNUCVersion = 0;
   Opts.HexFloats = Std.hasHexFloats();

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 535d9c9de13d2c3235c9a1ef9c86a9e79c1dc230..8fb9975b8404e743fa4240d3156822e02608d8c4 100644 (file)
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1397,6 +1397,7 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
       !Args.hasArg(options::OPT_fmodules) && Std &&
       (Std->containsValue("c++20") || Std->containsValue("c++2a") ||
        Std->containsValue("c++23") || Std->containsValue("c++2b") ||
+       Std->containsValue("c++26") || Std->containsValue("c++2c") ||
        Std->containsValue("c++latest"));
 
   // Process -fmodule-header{=} flags.

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 31f2881be6b62b4cd8b33b47ecf9d913e0241abc..383984e59034e306206862fa3cd094dbe9a2412f 100644 (file)
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3674,6 +3674,7 @@ static bool RenderModulesOptions(Compilation &C, const Driver &D,
       IsCXX && Std &&
       (Std->containsValue("c++2a") || Std->containsValue("c++20") ||
        Std->containsValue("c++2b") || Std->containsValue("c++23") ||
+       Std->containsValue("c++2c") || Std->containsValue("c++26") ||
        Std->containsValue("c++latest"));
   bool HaveModules = HaveStdCXXModules;
 
@@ -6660,8 +6661,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                              .Case("c++14", "-std=c++14")
                              .Case("c++17", "-std=c++17")
                              .Case("c++20", "-std=c++20")
-                             // TODO add c++23 when MSVC supports it.
-                             .Case("c++latest", "-std=c++23")
+                             // TODO add c++23 and c++26 when MSVC supports it.
+                             .Case("c++latest", "-std=c++26")
                              .Default("");
       if (LanguageStandard.empty())
         D.Diag(clang::diag::warn_drv_unused_argument)

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 822109c389360375c228bbc40d72468156299615..8082a1924802b5b3f17cdde081978728cbef07dd 100644 (file)
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -451,7 +451,10 @@ static void InitializeStandardPredefinedMacros(const TargetInfo &TI,
       Builder.defineMacro("__STDC_VERSION__", "199409L");
   } else {
     //   -- __cplusplus
-    if (LangOpts.CPlusPlus23)
+    if (LangOpts.CPlusPlus26)
+      // FIXME: Use correct value for C++26.
+      Builder.defineMacro("__cplusplus", "202400L");
+    else if (LangOpts.CPlusPlus23)
       Builder.defineMacro("__cplusplus", "202302L");
     //      [C++20] The integer literal 202002L.
     else if (LangOpts.CPlusPlus20)

diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index b32b44ab3164871b7ea2ac61c7bee814b2053abe..12d7023bd61b1e31139ec7616d1c2d7a58e03726 100644 (file)
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -604,7 +604,7 @@
 // STDCXX20: -std=c++20
 
 // RUN: %clang_cl -fmsc-version=1900 -TP -std:c++latest -### -- %s 2>&1 | FileCheck -check-prefix=STDCXXLATEST %s
-// STDCXXLATEST: -std=c++23
+// STDCXXLATEST: -std=c++26
 
 // RUN: env CL="/Gy" %clang_cl -### -- %s 2>&1 | FileCheck -check-prefix=ENV-CL %s
 // ENV-CL: "-ffunction-sections"

diff --git a/clang/test/Driver/unknown-std.cpp b/clang/test/Driver/unknown-std.cpp
index 1490e9e3a1164f768b9ba2de06ff434330e380c9..e918c087095ef051ccb8d5af3e64cca51985597b 100644 (file)
--- a/clang/test/Driver/unknown-std.cpp
+++ b/clang/test/Driver/unknown-std.cpp
@@ -19,6 +19,8 @@
 // CHECK-NEXT: note: use 'gnu++20' for 'ISO C++ 2020 DIS with GNU extensions' standard
 // CHECK-NEXT: note: use 'c++23' for 'ISO C++ 2023 DIS' standard
 // CHECK-NEXT: note: use 'gnu++23' for 'ISO C++ 2023 DIS with GNU extensions' standard
+// CHECK-NEXT: note: use 'c++2c' or 'c++26' for 'Working draft for C++2c' standard
+// CHECK-NEXT: note: use 'gnu++2c' or 'gnu++26' for 'Working draft for C++2c with GNU extensions' standard
 // CUDA-NEXT: note: use 'cuda' for 'NVIDIA CUDA(tm)' standard
 
 // Make sure that no other output is present.

diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
index 661808e34c872dc950ebf04aa28083506cc89a19..a45a22b7008caa259fac99a5d88f74461a9cd1a4 100644 (file)
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -8,6 +8,15 @@
 // BLOCKS:#define __BLOCKS__ 1
 // BLOCKS:#define __block __attribute__((__blocks__(byref)))
 //
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++26 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX26 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++2c -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX26 %s
+//
+// CXX26:#define __GNUG__ 4
+// CXX26:#define __GXX_EXPERIMENTAL_CXX0X__ 1
+// CXX26:#define __GXX_RTTI 1
+// CXX26:#define __GXX_WEAK__ 1
+// CXX26:#define __cplusplus 202402L
+// CXX26:#define __private_extern__ extern
 //
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++23 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2B %s
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++2b -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2B %s
@@ -134,6 +143,14 @@
 // RUN: %clang_cc1 -ffreestanding -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix FREESTANDING %s
 // FREESTANDING:#define __STDC_HOSTED__ 0
 //
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++26 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX26 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++2c -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX26 %s
+//
+// GXX26:#define __GNUG__ 4
+// GXX26:#define __GXX_WEAK__ 1
+// GXX26:#define __cplusplus 202402L
+// GXX26:#define __private_extern__ extern
+//
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++23 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2B %s
 // RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++2b -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2B %s
 //

diff --git a/clang/www/OpenProjects.html b/clang/www/OpenProjects.html
index d3aedd281121c220e5f234f0d199eeed7a31e583..7a8bdbd3dbbc80705d5002ebc6556bdc6b58d6ba 100755 (executable)
--- a/clang/www/OpenProjects.html
+++ b/clang/www/OpenProjects.html
@@ -123,7 +123,7 @@ improve the quality of clang by self-testing. Some examples:
 </ul>
 </li>
 
-<li><b>Continue work on C++20, C++23, and C2x support</b>:
+<li><b>Continue work on C++20, C++23, C++2c, and C2x support</b>:
   There are still several C++20 features to complete, and work has begun on
   supporting the latest language standards. Please see the
   <a href="cxx_status.html">C++ status report page</a> to find out what is

diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
index dd45b3c2418cfe0dcf03bdc0537ca56f83bd8b9c..564c3d6a8c48c3822fd3de89636c7c2ec09cbb84 100755 (executable)
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -65,6 +65,11 @@
  <td><tt>-std=c++23</tt></td>
  <td class="partial" align="center">Partial</td>
 </tr>
+<tr>
+ <td><a href="#cxx26">C++2c</a></td>
+ <td><tt>-std=c++2c</tt></td>
+ <td class="partial" align="center">Partial</td>
+</tr>
 </table>
 
 <p>The Clang community is continually striving to improve C++ standards
@@ -1560,6 +1565,25 @@ code. This issue is expected to be rectified soon.
 </table>
 </details>
 
+<h2 id="cxx26">C++2c implementation status</h2>
+
+<!-- TODO add link to the ISO Standard after it's published. -->
+<p>Clang has support for some of the features of the C++ standard following
+C++23, informally referred to as C++26.</p>
+
+<p>You can use Clang in C++2c mode with the <code>-std=c++2c</code> option.</p>
+
+<details open>
+<summary>List of features and minimum Clang version with support</summary>
+<table width="689" border="1" cellspacing="0">
+ <tr>
+    <th>Language Feature</th>
+    <th>C++26 Proposal</th>
+    <th>Available in Clang?</th>
+ </tr>
+ </table>
+ </details>
+
 <h2 id="dr">Defect reports</h2>
 
 <p>Clang generally aims to implement resolutions to Defect Reports (bug fixes