[clang] [clang-tools-extra] [libcxx] [clang] Enable sized deallocation by default in C++14 onwards (PR #83774)

[Fangrui Song via cfe-commits]

================
@@ -7238,10 +7238,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.addOptInFlag(CmdArgs, options::OPT_frelaxed_template_template_args,
                     options::OPT_fno_relaxed_template_template_args);
 
-  // -fsized-deallocation is off by default, as it is an ABI-breaking change for
-  // most platforms.
-  Args.addOptInFlag(CmdArgs, options::OPT_fsized_deallocation,
-                    options::OPT_fno_sized_deallocation);
+  // -fsized-deallocation is on by default in C++14 onwards and otherwise off
+  // by default.
+  if (Arg *A = Args.getLastArg(options::OPT_fsized_deallocation,
+                               options::OPT_fno_sized_deallocation)) {
+    if (A->getOption().matches(options::OPT_fno_sized_deallocation))
+      CmdArgs.push_back("-fno-sized-deallocation");
----------------
MaskRay wrote:

I see. There are many -fsize-deallocation in existing tests. I can clean up them this patch lands.

https://github.com/llvm/llvm-project/pull/83774