Add ABI_VER_LATEST macro

Author: zwuis

clang/include/clang/Basic/ABIVersions.def

@@ -12,18 +12,21 @@
 //
 /// @file ABIVersions.def
 ///
-/// In this file, each of the Clang ABI Versions except "latest" is enumerated
-/// ABI_VER_MAJOR_MINOR, or ABI_VER_MAJOR macro.
+/// In this file, each of the Clang ABI Versions is enumerated
+/// ABI_VER_MAJOR_MINOR, ABI_VER_MAJOR, or ABI_VER_LATEST macro.
 ///
 /// ABI_VER_MAJOR is used when the minor version is 0 or can be omitted.
 ///
 /// The first argument of ABI_VER_MAJOR_MINOR and ABI_VER_MAJOR is the major
 /// version.
 ///
 /// The second argument of ABI_VER_MAJOR_MINOR is the minor version.
+///
+/// The first argument of ABI_VER_LATEST is an identifier `Latest`.
 
-#if defined(ABI_VER_MAJOR_MINOR) != defined(ABI_VER_MAJOR)
-#  error ABI_VER_MAJOR_MINOR and ABI_VER_MAJOR should be defined simultaneously
+#if defined(ABI_VER_MAJOR_MINOR) != defined(ABI_VER_MAJOR) ||                  \
+    defined(ABI_VER_MAJOR) != defined(ABI_VER_LATEST)
+#  error ABI_VER_MAJOR_MINOR, ABI_VER_MAJOR and ABI_VER_LATEST should be defined simultaneously
 #endif
 
 #ifndef ABI_VER_MAJOR_MINOR
@@ -34,6 +37,10 @@
 #  define ABI_VER_MAJOR(Major)
 #endif
 
+#ifndef ABI_VER_LATEST
+#  define ABI_VER_LATEST(Latest)
+#endif
+
 /// Attempt to be ABI-compatible with code generated by Clang 3.8.x
 /// (SVN r257626). This causes <1 x long long> to be passed in an integer
 /// register instead of an SSE register on x64_64.
@@ -121,7 +128,8 @@ ABI_VER_MAJOR(19)
 ABI_VER_MAJOR(20)
 
 /// Conform to the underlying platform's C and C++ ABIs as closely as we can.
-// (latest)
+ABI_VER_LATEST(Latest)
 
 #undef ABI_VER_MAJOR_MINOR
 #undef ABI_VER_MAJOR
+#undef ABI_VER_LATEST

clang/include/clang/Basic/LangOptions.h

@@ -188,9 +188,8 @@ class LangOptionsBase {
   enum class ClangABI {
 #define ABI_VER_MAJOR_MINOR(Major, Minor) Ver##Major##_##Minor,
 #define ABI_VER_MAJOR(Major) Ver##Major,
+#define ABI_VER_LATEST(Latest) Latest
 #include "clang/Basic/ABIVersions.def"
-
-    Latest
   };
 
   enum class CoreFoundationABI {

clang/lib/Frontend/CompilerInvocation.cpp

@@ -3944,10 +3944,10 @@ void CompilerInvocationBase::GenerateLangArgs(const LangOptions &Opts,
   case LangOptions::ClangABI::Ver##Major:                                      \
     GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, #Major ".0");              \
     break;
-#include "clang/Basic/ABIVersions.def"
-
-  case LangOptions::ClangABI::Latest:
+#define ABI_VER_LATEST(Latest)                                                 \
+  case LangOptions::ClangABI::Latest:                                          \
     break;
+#include "clang/Basic/ABIVersions.def"
   }
 
   if (Opts.getSignReturnAddressScope() ==
@@ -4461,8 +4461,10 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
   if (Major <= Major_)                                                         \
     Opts.setClangABICompat(LangOptions::ClangABI::Ver##Major_);                \
   else
+#define ABI_VER_LATEST(Latest)                                                 \
+  { /* Equivalent to latest version - do nothing */                            \
+  }
 #include "clang/Basic/ABIVersions.def"
-      {} // sub-statement of the last else branch
     } else if (Ver != "latest") {
       Diags.Report(diag::err_drv_invalid_value)
           << A->getAsString(Args) << A->getValue();