[PATCH] D150450: Add C++26 compile flags.

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/docs/CommandGuide/clang.rst:206-210
+   Working draft for ISO C++ 2026
+
+  | ``gnu++2c``
+
+   Working draft for ISO C++ 2026 with GNU extensions
----------------
We shouldn't call it `ISO C++ 2026` until it's published by ISO. (I don't have strong opinions about 2c vs 26 in there, but since we need to update it anyway when 26 is released, I figured it'd be easier to find again with 2c.)


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Comment at: clang/docs/ReleaseNotes.rst:114
+^^^^^^^^^^^^^^^^^^^^^
+- Compiler flags -std=c++2c and -std=gnu++2c have been added for experimental C++2c implementation work.
+
----------------



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Comment at: clang/include/clang/Basic/DiagnosticGroups.td:1120
+// earlier C++ versions.
+def CXX26 : DiagGroup<"c++26-extensions">;
+
----------------
Same here as above.


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Comment at: clang/include/clang/Basic/DiagnosticGroups.td:310
   DiagGroup<"pre-c++23-compat-pedantic", [CXXPre23Compat]>;
+def CXXPre26Compat : DiagGroup<"pre-c++26-compat">;
+def CXXPre26CompatPedantic :
----------------
erichkeane wrote:
> Aaron: note the names of the diag groups: would you prefer this to be `c++2c`?
Let's go ahead and add the alias so that either c++2c or c++26 works.


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Comment at: clang/include/clang/Basic/LangOptions.def:101
 LANGOPT(CPlusPlus23       , 1, 0, "C++23")
+LANGOPT(CPlusPlus26       , 1, 0, "C++26")
 LANGOPT(ObjC              , 1, 0, "Objective-C")
----------------
erichkeane wrote:
> It isn't clear to me what the string here is used to output, so not sure if this should be 2c.
The only place this matters is when dumping information about a module file for debugging purposes, so I don't think it's critical this be named 2c.


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Comment at: clang/include/clang/Basic/LangStandard.h:128
+
+  // hasDigraphs - Language supports digraphs.
   bool hasDigraphs() const { return Flags & Digraphs; }
----------------
h-vetinari wrote:
> Spuriously removed slash



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Comment at: clang/include/clang/Basic/LangStandards.def:167
+LANGSTANDARD(cxx26, "c++2c",
+             CXX, "Working draft for ISO C++ 2026 DIS",
+             LineComment | CPlusPlus | CPlusPlus11 | CPlusPlus14 | CPlusPlus17 |
----------------
We should probably drop `ISO` from this as we did above?


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Comment at: clang/lib/Frontend/InitPreprocessor.cpp:456
+      // FIXME: Use correct value for C++26.
+      Builder.defineMacro("__cplusplus", "202402L");
+    else if (LangOpts.CPlusPlus23)
----------------
This value is fine by me, but we should probably coordinate with the GCC folks so we don't wind up with two different values between us.


================
Comment at: clang/lib/Frontend/InitPreprocessor.cpp:458
+    else if (LangOpts.CPlusPlus23)
+      Builder.defineMacro("__cplusplus", "202302L");
     //      [C++20] The integer literal 202002L.
----------------
xbolva00 wrote:
> Separate patch / commit?
Agreed, the change for C++23 should be done in a separate patch.


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Comment at: clang/www/OpenProjects.html:126
 
-<li><b>Continue work on C++20, C++23, and C2x support</b>:
+<li><b>Continue work on C++20, C++23, C++26, and C2x support</b>:
   There are still several C++20 features to complete, and work has begun on
----------------
cor3ntin wrote:
> erichkeane wrote:
> > Should this spot in the docs be `C++2c`?
> I think so
Agreed -- basically, if it's user-facing, it should be 2c, and if it's internal to the project, it should be 26.


================
Comment at: clang/www/cxx_status.html:1568
 
+<h2 id="cxx26">C++2c implementation status</h2>
+
----------------
cor3ntin wrote:
> h-vetinari wrote:
> > The longer this page gets, the more I feel it should be sorted in reverse chronological order of the standard versions. It's bothersome IMO to keep scrolling past almost-fully implemented standards (currently the tables for C++17 & C++20) before getting to see the status of the latest & greatest. 
> > 
> > https://en.cppreference.com/w/cpp/compiler_support is sorted in reverse order as well.
> This sounds like an excellent improvement.
> Erich, would you rather do that in this pr, or i can submit a different patch afterwards?
I love the idea, and I think it should be done in a separate patch.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D150450/new/

https://reviews.llvm.org/D150450