[PATCH] D114576: [PR52549][clang-cl] Predefine _MSVC_EXECUTION_CHARACTER_SET

[Markus Böck via Phabricator via cfe-commits]

zero9178 created this revision.
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Since VS 2022 17.1 MSVC predefines _MSVC_EXECUTION_CHARACTER_SET to inform the users of the execution character set defined at compile time. The value the macro expands to is a Windows Code Page Identifier which are documented here: https://docs.microsoft.com/en-us/windows/win32/intl/code-page-identifiers

As clang currently only supports UTF-8 it is defined as 65001. If clang-cl were to support a different execution character set in the future we'd have to change the value.

Fixes https://bugs.llvm.org/show_bug.cgi?id=52549


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114576

Files:
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/Driver/cl-execution-character-set.c


Index: clang/test/Driver/cl-execution-character-set.c
===================================================================
--- /dev/null
+++ clang/test/Driver/cl-execution-character-set.c
@@ -0,0 +1,7 @@
+// 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.
+
+// Only UTF-8 is currently supported, which has the Windows Code
+// Page Identifier 65001
+// RUN: %clang_cl -### -- %s 2>&1 | FileCheck %s
+// CHECK: -D_MSVC_EXECUTION_CHARACTER_SET=65001
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -7327,6 +7327,14 @@
     CmdArgs.push_back("--dependent-lib=oldnames");
   }
 
+  // Starting with VS 2022 17.1, MSVC predefines the below macro to inform
+  // users of the execution character set defined at compile time.
+  // The value given is the Windows Code Page Identifier:
+  // https://docs.microsoft.com/en-us/windows/win32/intl/code-page-identifiers
+  //
+  // Clang currently only supports UTF-8, so we'll use 65001
+  CmdArgs.push_back("-D_MSVC_EXECUTION_CHARACTER_SET=65001");
+
   if (Arg *ShowIncludes =
           Args.getLastArg(options::OPT__SLASH_showIncludes,
                           options::OPT__SLASH_showIncludes_user)) {


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