[PATCH] D127641: [clang-cl][MSVC] Enable /Zc:alignedNew for C++17 and /Zc:sizedDealloc by default

[Stephen Long via Phabricator via cfe-commits]

steplong updated this revision to Diff 437243.
steplong added a comment.

`https://docs.microsoft.com/en-us/cpp/build/reference/zc-sizeddealloc-enable-global-sized-dealloc-functions?view=msvc-170` says it implements this by default starting on MSVC 2015. I don't have an older version of MSVC, so maybe someone can confirm for me


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127641/new/

https://reviews.llvm.org/D127641

Files:
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/Driver/cl-zc.cpp


Index: clang/test/Driver/cl-zc.cpp
===================================================================
--- clang/test/Driver/cl-zc.cpp
+++ clang/test/Driver/cl-zc.cpp
@@ -1,6 +1,19 @@
 // Note: %s must be preceded by --, otherwise it may be interpreted as a
 // command-line option, e.g. on Mac where %s is commonly under /Users.
 
+// RUN: %clang_cl /c -### -- %s 2>&1 | FileCheck -check-prefix=SIZED-DEALLOC-DEFAULT %s
+// RUN: %clang_cl /c -### -fms-compatibility-version=18 -- %s 2>&1 | FileCheck -check-prefix=SIZED-DEALLOC-OFF-DEFAULT %s
+// SIZED-DEALLOC-DEFAULT: "-fsized-deallocation"
+// SIZED-DEALLOC-OFF-DEFAULT-NOT: "-fsized-deallocation"
+
+// RUN: %clang_cl /c /std:c++11 -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-BEFORE-CPP17-DEFAULT %s
+// RUN: %clang_cl /c /std:c++14 -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-BEFORE-CPP17-DEFAULT %s
+// RUN: %clang_cl /c /std:c++17 -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-CPP17ONWARDS-DEFAULT %s
+// RUN: %clang_cl /c /std:c++20 -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-CPP17ONWARDS-DEFAULT %s
+// RUN: %clang_cl /c /std:c++latest -### -- %s 2>&1 | FileCheck -check-prefix=ALIGNED-NEW-CPP17ONWARDS-DEFAULT %s
+// ALIGNED-NEW-BEFORE-CPP17-DEFAULT-NOT: "-faligned-allocation"
+// ALIGNED-NEW-CPP17ONWARDS-DEFAULT: "-faligned-allocation"
+
 // RUN: %clang_cl /c -### -- %s 2>&1 | FileCheck -check-prefix=TRIGRAPHS-DEFAULT %s
 // cc1 will disable trigraphs for -fms-compatibility as long as -ftrigraphs
 // isn't explicitly passed.
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -6483,6 +6483,7 @@
     }
     CmdArgs.push_back(LanguageStandard.data());
   }
+  bool IsCPP17Onwards = false;
   if (ImplyVCPPCXXVer) {
     StringRef LanguageStandard;
     if (const Arg *StdArg = Args.getLastArg(options::OPT__SLASH_std)) {
@@ -6506,6 +6507,9 @@
     }
 
     CmdArgs.push_back(LanguageStandard.data());
+
+    IsCPP17Onwards =
+        LanguageStandard != "-std=c++11" && LanguageStandard != "-std=c++14";
   }
 
   Args.addOptInFlag(CmdArgs, options::OPT_fborland_extensions,
@@ -6635,9 +6639,15 @@
                     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);
+  // most platforms. MSVC turns on /Zc:sizedDealloc by default, starting in
+  // MSVC 2015.
+  if (IsWindowsMSVC && IsMSVC2015Compatible &&
+      !Args.getLastArg(options::OPT_fsized_deallocation,
+                       options::OPT_fno_sized_deallocation))
+    CmdArgs.push_back("-fsized-deallocation");
+  else
+    Args.addOptInFlag(CmdArgs, options::OPT_fsized_deallocation,
+                      options::OPT_fno_sized_deallocation);
 
   // -faligned-allocation is on by default in C++17 onwards and otherwise off
   // by default.
@@ -6648,6 +6658,8 @@
       CmdArgs.push_back("-fno-aligned-allocation");
     else
       CmdArgs.push_back("-faligned-allocation");
+  } else if (IsCPP17Onwards) {
+    CmdArgs.push_back("-faligned-allocation");
   }
 
   // The default new alignment can be specified using a dedicated option or via


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