/*
  Copyright Kitware, Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      https://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
*/

#include "RunClang.h"
#include "Options.h"
#include "Output.h"
#include "Utils.h"

#include "llvm/Config/llvm-config.h"

#if LLVM_VERSION_MAJOR >= 17
#  include "llvm/TargetParser/Host.h"
#else
#  include "llvm/Support/Host.h"
#endif

#include "clang/AST/ASTConsumer.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/Version.h"
#include "clang/Driver/Compilation.h"
#include "clang/Driver/Driver.h"
#include "clang/Driver/DriverDiagnostic.h"
#include "clang/Driver/Options.h"
#include "clang/Driver/Tool.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/FrontendActions.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/TextDiagnosticPrinter.h"
#include "clang/Frontend/Utils.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/Sema.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"

#if LLVM_VERSION_MAJOR >= 20
#  include "llvm/Support/VirtualFileSystem.h"
#endif

#include <cstdlib>
#include <fstream>
#include <iostream>
#include <memory>
#include <queue>

#if LLVM_VERSION_MAJOR > 3 ||                                                 \
  LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR >= 9
#  define CASTXML_OWNS_OSTREAM
#endif

#if LLVM_VERSION_MAJOR >= 10
#  define CASTXML_MAKE_UNIQUE std::make_unique
#else
#  define CASTXML_MAKE_UNIQUE llvm::make_unique
#endif

class ASTConsumer : public clang::ASTConsumer
{
  clang::CompilerInstance& CI;
#ifdef CASTXML_OWNS_OSTREAM
  std::unique_ptr<llvm::raw_ostream> OwnOS;
#endif
  llvm::raw_ostream& OS;
  Options const& Opts;
  struct Class
  {
    clang::CXXRecordDecl* RD;
    int Depth;
    Class(clang::CXXRecordDecl* rd, int depth)
      : RD(rd)
      , Depth(depth)
    {
    }
  };
  std::queue<Class> Classes;
  int ClassImplicitMemberDepth = 0;

public:
#ifdef CASTXML_OWNS_OSTREAM
  ASTConsumer(clang::CompilerInstance& ci,
              std::unique_ptr<llvm::raw_ostream> os, Options const& opts)
    : CI(ci)
    , OwnOS(std::move(os))
    , OS(*OwnOS)
    , Opts(opts)
  {
  }
#else
  ASTConsumer(clang::CompilerInstance& ci, llvm::raw_ostream& os,
              Options const& opts)
    : CI(ci)
    , OS(os)
    , Opts(opts)
  {
  }
#endif

  void AddImplicitMembers(Class const& c)
  {
    clang::CXXRecordDecl* rd = c.RD;
    this->ClassImplicitMemberDepth = c.Depth + 1;

    clang::Sema& sema = this->CI.getSema();
    sema.ForceDeclarationOfImplicitMembers(rd);

    for (clang::DeclContext::decl_iterator i = rd->decls_begin(),
                                           e = rd->decls_end();
         i != e; ++i) {
      clang::CXXMethodDecl* m = clang::dyn_cast<clang::CXXMethodDecl>(*i);
      if (m && !m->isDeleted() && !m->isInvalidDecl()) {
        bool mark = false;
        clang::CXXConstructorDecl* c =
          clang::dyn_cast<clang::CXXConstructorDecl>(m);
        if (c) {
          mark = (c->isDefaultConstructor() || c->isCopyConstructor() ||
                  c->isMoveConstructor());
        } else if (clang::dyn_cast<clang::CXXDestructorDecl>(m)) {
          mark = true;
        } else {
          mark =
            (m->isCopyAssignmentOperator() || m->isMoveAssignmentOperator());
        }
        if (mark) {
          clang::DiagnosticErrorTrap Trap(sema.getDiagnostics());
          /* Ensure the member is defined.  */
          sema.MarkFunctionReferenced(clang::SourceLocation(), m);
          if (c && c->isDefaulted() && c->isDefaultConstructor() &&
              c->isTrivial() && !c->isUsed(false) &&
              !c->hasAttr<clang::DLLExportAttr>()) {
            /* Clang does not build the definition of trivial constructors
               until they are used.  Force semantic checking.  */
            sema.DefineImplicitDefaultConstructor(clang::SourceLocation(), c);
          }
          if (Trap.hasErrorOccurred()) {
            m->setInvalidDecl();
          }
          /* Finish implicitly instantiated member.  */
          sema.PerformPendingInstantiations();
        }
      }
    }
  }

  void HandleTagDeclDefinition(clang::TagDecl* d)
  {
    if (clang::CXXRecordDecl* rd = clang::dyn_cast<clang::CXXRecordDecl>(d)) {
      if (!rd->isDependentContext()) {
        if (this->ClassImplicitMemberDepth < 16) {
          this->Classes.push(Class(rd, this->ClassImplicitMemberDepth));
        }
      }
    }
  }

  void HandleTranslationUnit(clang::ASTContext& ctx)
  {
    clang::Sema& sema = this->CI.getSema();

    // Perform instantiations needed by the original translation unit.
    sema.PerformPendingInstantiations();

    if (!sema.getDiagnostics().hasErrorOccurred()) {
      // Suppress diagnostics from below extensions to the translation unit.
      sema.getDiagnostics().setSuppressAllDiagnostics(true);

      // Add implicit members to classes.
      while (!this->Classes.empty()) {
        Class c = this->Classes.front();
        this->Classes.pop();
        this->AddImplicitMembers(c);
      }
    }

    // Tell Clang to finish the translation unit and tear down the parser.
    sema.ActOnEndOfTranslationUnit();

    // Process the AST.
    outputXML(this->CI, ctx, this->OS, this->Opts);
  }
};

template <class T>
class CastXMLPredefines : public T
{
protected:
  Options const& Opts;

  CastXMLPredefines(Options const& opts)
    : Opts(opts)
  {
  }
  std::string UpdatePredefines(clang::CompilerInstance const& CI)
  {
    std::string const& predefines = CI.getPreprocessor().getPredefines();

    // Identify the portion of the predefines string corresponding to
    // built-in predefined macros.
    char const predef_start[] = "# 1 \"<built-in>\" 3\n";
    char const predef_end[] = "# 1 \"<command line>\" 1\n";
    std::string::size_type start = predefines.find(predef_start);
    std::string::size_type end = std::string::npos;
    if (start != std::string::npos) {
      start += sizeof(predef_start) - 1;
      end = predefines.find(predef_end, start);
      if (end == std::string::npos) {
        end = predefines.size();
      }
    }

    std::string builtins;

    // Add builtins to identify CastXML itself.
    {
      char castxml_version[64];
      sprintf(castxml_version, "#define __castxml_major__ %u\n",
              getVersionMajor());
      builtins += castxml_version;
      sprintf(castxml_version, "#define __castxml_minor__ %u\n",
              getVersionMinor());
      builtins += castxml_version;
      sprintf(castxml_version, "#define __castxml_patch__ %u\n",
              getVersionPatch());
      builtins += castxml_version;
    }
    // Encode the version number components to allow a date as the patch
    // level and up to 1000 minor releases for each major release.
    // These values can exceed a 32-bit unsigned integer, but we know
    // that they will only be evaluated by our builtin clang.
    builtins += "#define __castxml_check(major,minor,patch) "
                "(10000000000*major + 100000000*minor + patch)\n";
    builtins += "#define __castxml__ "
                "__castxml_check(__castxml_major__,__castxml_minor__,"
                "__castxml_patch__)\n";

    // Add builtins to identify the internal Clang compiler.
    builtins +=
#define STR(x) STR_(x)
#define STR_(x) #x
      "#define __castxml_clang_major__ " STR(
        CLANG_VERSION_MAJOR) "\n"
                             "#define __castxml_clang_minor__ " STR(
                               CLANG_VERSION_MINOR) "\n"
                                                    "#define "
                                                    "__castxml_clang_"
                                                    "patchlevel__ "
#ifdef CLANG_VERSION_PATCHLEVEL
      STR(CLANG_VERSION_PATCHLEVEL)
#else
                                                    "0"
#endif
        "\n"
#undef STR
#undef STR_
      ;

    // If we detected predefines from another compiler, substitute them.
    if (this->Opts.HaveCC) {
      builtins += this->Opts.Predefines;

      // Remove GCC builtin definitions for features Clang does not implement.
      if (this->IsActualGNU(this->Opts.Predefines)) {
        builtins += "#undef __BFLT16_DECIMAL_DIG__\n"
                    "#undef __BFLT16_DENORM_MIN__\n"
                    "#undef __BFLT16_DIG__\n"
                    "#undef __BFLT16_DIG__\n"
                    "#undef __BFLT16_EPSILON__\n"
                    "#undef __BFLT16_HAS_DENORM__\n"
                    "#undef __BFLT16_HAS_INFINITY__\n"
                    "#undef __BFLT16_HAS_QUIET_NAN__\n"
                    "#undef __BFLT16_IS_IEC_60559__\n"
                    "#undef __BFLT16_MANT_DIG__\n"
                    "#undef __BFLT16_MAX_10_EXP__\n"
                    "#undef __BFLT16_MAX_EXP__\n"
                    "#undef __BFLT16_MAX__\n"
                    "#undef __BFLT16_MIN_10_EXP__\n"
                    "#undef __BFLT16_MIN_EXP__\n"
                    "#undef __BFLT16_MIN__\n"
                    "#undef __BFLT16_NORM_MAX__\n"
                    "#undef __STDCPP_BFLOAT16_T__\n"
                    "#undef __STDCPP_FLOAT128_T__\n"
                    "#undef __STDCPP_FLOAT16_T__\n"
                    "#undef __STDCPP_FLOAT32_T__\n"
                    "#undef __STDCPP_FLOAT64_T__\n";
      }

      // Provide __builtin_va_arg_pack if simulating the actual GNU compiler.
      if (this->NeedBuiltinVarArgPack(this->Opts.Predefines)) {
        // Clang does not support this builtin, so fake it to tolerate
        // uses in function bodies while parsing.
        builtins += "\n"
                    "#define __builtin_va_arg_pack() 0\n"
                    "#define __builtin_va_arg_pack_len() 1\n";
      }

      // Provide __float80 if simulating the actual GNU compiler.
      if (this->NeedFloat80(this->Opts.Predefines)) {
        // Clang does not support this builtin.  Approximate it.
        builtins += "\n"
                    "typedef long double __castxml__float80;\n"
                    "#define __float80 __castxml__float80\n";
      }

      // Provide __float128 if simulating the actual GNU compiler.
      if (!this->HaveFloat128(CI) &&
          this->NeedFloat128(this->Opts.Predefines)) {
        // Clang provides its own (fake) builtin in gnu++11 mode but issues
        // diagnostics when it is used in some contexts.  Provide our own
        // approximation of the builtin instead.
        builtins += "\n"
                    "typedef struct __castxml__float128_s { "
                    "  char x[16] __attribute__((aligned(16))); "
                    "} __castxml__float128;\n"
                    "#define __float128 __castxml__float128\n";
      }

      if (CI.getLangOpts().MSCompatibilityVersion >= 192300000) {
        // MSVC tools 14.23 and above declare __builtin_assume_aligned
        // in "intrin0.h" with a signature incompatible with Clang's
        // builtin.  It is guarded by '!defined(__clang__)' but that
        // breaks when we simulate MSVC's preprocessor.  Rename the
        // builtin via preprocessing to avoid the conflict.
        builtins += "\n"
                    "#define __builtin_assume_aligned"
                    " __castxml__builtin_assume_aligned\n";
      }

      // Provide __is_assignable builtin if simulating MSVC.
      // When a future Clang version supports the builtin then
      // we can skip this when built against such a Clang.
      if (CI.getLangOpts().MSCompatibilityVersion >= 190000000 &&
          CI.getLangOpts().CPlusPlus11) {
        builtins +=
          "\n"
          "template <typename T> T&& __castxml__declval() noexcept;\n"
          "template <typename To, typename Fr, typename =\n"
          "  decltype(__castxml__declval<To>() = __castxml__declval<Fr>())>\n"
          "  static char (&__castxml__is_assignable_check(int))[1];\n"
          "template <typename, typename>\n"
          "  static char (&__castxml__is_assignable_check(...))[2];\n"
          "#define __is_assignable(_To,_Fr) \\\n"
          "  (sizeof(__castxml__is_assignable_check<_To,_Fr>(0)) == \\\n"
          "   sizeof(char(&)[1]))\n";
      }

#if LLVM_VERSION_MAJOR < 3 || LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR < 8
      // Clang 3.8 and above provide a __make_integer_seq builtin needed
      // in C++14 mode.  Provide it ourselves for older Clang versions.
      if (CI.getLangOpts().CPlusPlus14) {
        builtins +=
          "\n"
          "template <typename _T, _T> struct __castxml__integral_constant;\n"
          "template <template<typename _U, _U...> class _S,\n"
          "          typename, typename, bool>\n"
          "  struct __castxml__make_integer_seq_impl;\n"
          "template <template<typename _U, _U...> class _S,\n"
          "          class _T, _T... __v>\n"
          "  struct __castxml__make_integer_seq_impl<_S,\n"
          "       __castxml__integral_constant<_T, 0>,\n"
          "       _S<_T, __v...>, true> {\n"
          "     typedef _S<_T, __v...> type;\n"
          "  };\n"
          "template <template<typename _U, _U...> class _S,\n"
          "          class _T, _T __i, _T... __v>\n"
          "  struct __castxml__make_integer_seq_impl<_S,\n"
          "       __castxml__integral_constant<_T, __i>,\n"
          "       _S<_T, __v...>, true>\n"
          "    : __castxml__make_integer_seq_impl<_S,\n"
          "       __castxml__integral_constant<_T, __i - 1>,\n"
          "       _S<_T, __i - 1, __v...>, __i >= 1 > {};\n"
          "template <template<typename _U, _U...> class _S,\n"
          "          typename _T, _T _Sz>\n"
          "using __castxml__make_integer_seq = typename\n"
          "  __castxml__make_integer_seq_impl<_S,\n"
          "      __castxml__integral_constant<_T, _Sz>,\n"
          "     _S<_T>, (_Sz>=0)>::type;\n"
          "#define __make_integer_seq __castxml__make_integer_seq\n";
      }
#endif

#if LLVM_VERSION_MAJOR < 6
      if (this->NeedHasUniqueObjectRepresentations(this->Opts.Predefines,
                                                   CI)) {
        // Clang 6 and above provide a __has_unique_object_representations
        // builtin needed in C++17 mode.  Provide an approximation for older
        // Clang versions.
        builtins += "\n"
                    "#define __has_unique_object_representations(x) false\n";
      }
#endif

      // Prevent glibc use of a GNU extension not implemented by Clang.
      if (this->NeedNoMathInlines(this->Opts.Predefines)) {
        builtins += "\n"
                    "#define __NO_MATH_INLINES 1\n";
      }

      // Tolerate glibc use of a GNU extension not implemented by Clang.
      if (this->NeedAttributeMallocArgs(this->Opts.Predefines)) {
        // Clang does not support '__attribute__((__malloc__(args...)))'
        // used in glibc 2.34+ headers.
        builtins += "\n"
                    "#define __malloc__(...) __malloc__\n";
      }
      if (this->NeedAttributeAssumeSuppression(this->Opts.Predefines)) {
        // Clang does not support '__attribute__((__assume__(args...)))'
        // as a statement attribute used in libstdc++ headers.
        builtins += "\n"
                    "#define __assume__(...)\n";
      }

      // Clang's arm_neon.h checks for a feature macro not defined by GCC.
      if (this->NeedARMv8Intrinsics(this->Opts.Predefines)) {
        builtins += "\n"
                    "#define __ARM_FEATURE_DIRECTED_ROUNDING 1\n";
      }

      // Provide _Float## types if simulating the actual GNU compiler.
      if (this->Need_Float(this->Opts.Predefines)) {
        // Clang does not have these types for all sizes.
        // Provide our own approximation of the builtins.
        builtins += "\n"
                    "#define _Float32 __castxml_Float32\n"
                    "#define _Float32x __castxml_Float32x\n"
                    "#define _Float64 __castxml_Float64\n"
                    "#define _Float64x __castxml_Float64x\n";
        if (this->NeedFloat128(this->Opts.Predefines)) {
          builtins += "#define _Float128 __castxml_Float128\n";
        }

        if (this->IsCPlusPlus(this->Opts.Predefines)) {
          // In C++ we need distinct types for template specializations
          // in glibc headers, but also need conversions.
          builtins += "\n"
                      "typedef struct __castxml_Float32_s { "
                      "  float x; "
                      "  operator float() const; "
                      "  __castxml_Float32_s(float); "
                      "} __castxml_Float32;\n"
                      "typedef struct __castxml_Float32x_s { "
                      "  double x; "
                      "  operator double() const; "
                      "  __castxml_Float32x_s(double); "
                      "} __castxml_Float32x;\n"
                      "typedef struct __castxml_Float64_s { "
                      "  double x; "
                      "  operator double() const; "
                      "  __castxml_Float64_s(double); "
                      "} __castxml_Float64;\n"
                      "typedef struct __castxml_Float64x_s { "
                      "  long double x; "
                      "  operator long double() const; "
                      "  __castxml_Float64x_s(long double); "
                      "} __castxml_Float64x;\n";
          if (this->NeedFloat128(this->Opts.Predefines)) {
            builtins += "typedef struct __castxml_Float128_s { "
                        "  __float128 x; "
                        "  operator __float128() const; "
                        "  __castxml_Float128_s(__float128); "
                        "} __castxml_Float128;\n";
          }

        } else {
          // In C we need real float types for conversions in glibc headers.
          builtins += "\n"
                      "typedef float __castxml_Float32;\n"
                      "typedef double __castxml_Float32x;\n"
                      "typedef double __castxml_Float64;\n"
                      "typedef long double __castxml_Float64x;\n";
          if (this->NeedFloat128(this->Opts.Predefines)) {
            builtins += "typedef __float128 __castxml_Float128;\n";
          }
        }
      }

    } else {
      builtins += predefines.substr(start, end - start);
    }
    return predefines.substr(0, start) + builtins + predefines.substr(end);
  }

  bool IsCPlusPlus(std::string const& pd) const
  {
    return pd.find("#define __cplusplus ") != pd.npos;
  }

  bool IsActualGNU(std::string const& pd) const
  {
    return (pd.find("#define __GNUC__ ") != pd.npos &&
            pd.find("#define __clang__ ") == pd.npos &&
            pd.find("#define __INTEL_COMPILER ") == pd.npos &&
            pd.find("#define __CUDACC__ ") == pd.npos &&
            pd.find("#define __PGI ") == pd.npos);
  }

  unsigned int GetGNUMajorVersion(std::string const& pd) const
  {
    if (const char* d = strstr(pd.c_str(), "#define __GNUC__ ")) {
      d += 17;
      if (const char* e = strchr(d, '\n')) {
        if (*(e - 1) == '\r') {
          --e;
        }
        std::string const ver_str(d, e - d);
        errno = 0;
        long ver = std::strtol(ver_str.c_str(), nullptr, 10);
        if (errno == 0 && ver > 0) {
          return static_cast<unsigned int>(ver);
        }
      }
    }
    return 0;
  }

  bool NeedBuiltinVarArgPack(std::string const& pd)
  {
    return this->IsActualGNU(pd);
  }

  bool NeedAttributeMallocArgs(std::string const& pd)
  {
    return this->IsActualGNU(pd);
  }

  bool NeedAttributeAssumeSuppression(std::string const& pd)
  {
    return this->IsActualGNU(pd);
  }

  bool NeedFloat80(std::string const& pd) const
  {
    return (this->IsActualGNU(pd) &&
            (pd.find("#define __i386__ ") != pd.npos ||
             pd.find("#define __x86_64__ ") != pd.npos ||
             pd.find("#define __ia64__ ") != pd.npos));
  }

  bool NeedFloat128(std::string const& pd) const
  {
    return this->NeedFloat80(pd);
  }

  bool HaveFloat128(clang::CompilerInstance const& CI) const
  {
#if LLVM_VERSION_MAJOR > 3 || LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR > 8
    return CI.getTarget().hasFloat128Type();
#else
    static_cast<void>(CI);
    return false;
#endif
  }

  bool Need_Float(std::string const& pd) const
  {
    if (this->IsActualGNU(pd)) {
      // gcc >= 7  provides _Float## types in C.
      if (!this->IsCPlusPlus(pd)) {
        return this->GetGNUMajorVersion(pd) >= 7;
      }
      // g++ >= 13 provides _Float## types in C++.
      if (this->GetGNUMajorVersion(pd) < 13) {
        return false;
      }
      // glibc 2.27 added bits/floatn-common.h to define _Float## types when
      // the compiler does not, but only knew about GCC 7+ _Float## types in C.
      // glibc 2.37 updated the conditions for GCC 13+ _Float## types in C++.
      for (Options::Include const& i : this->Opts.Includes) {
        if (i.Framework) {
          continue;
        }
        if (std::ifstream f{ i.Directory + "/bits/floatn-common.h" }) {
          std::string h{ std::istreambuf_iterator<char>(f),
                         std::istreambuf_iterator<char>() };
          // If the header contains the pre-2.37 condition then
          // let it handle defining the _Float## types.
          if (h.find("if !__GNUC_PREREQ (7, 0) || defined __cplusplus") !=
              std::string::npos) {
            return false;
          }
          break;
        }
      }
      return true;
    }
    return false;
  }

#if LLVM_VERSION_MAJOR < 6
  bool NeedHasUniqueObjectRepresentations(
    std::string const& pd, clang::CompilerInstance const& CI) const
  {
    return (this->IsActualGNU(pd) && CI.getLangOpts().CPlusPlus1z);
  }
#endif

  bool NeedNoMathInlines(std::string const& pd) const
  {
    return (this->IsActualGNU(pd) &&
            (pd.find("#define __i386__ ") != pd.npos &&
             pd.find("#define __OPTIMIZE__ ") != pd.npos &&
             pd.find("#define __NO_MATH_INLINES ") == pd.npos));
  }

  bool NeedARMv8Intrinsics(std::string const& pd)
  {
    if (const char* d = strstr(pd.c_str(), "#define __ARM_ARCH ")) {
      d += 19;
      if (pd.find("#define __ARM_FEATURE_DIRECTED_ROUNDING ") != pd.npos) {
        return false;
      }
      if (const char* e = strchr(d, '\n')) {
        if (*(e - 1) == '\r') {
          --e;
        }
        std::string const arm_arch_str(d, e - d);
        errno = 0;
        long arm_arch = std::strtol(arm_arch_str.c_str(), nullptr, 10);
        if (errno == 0 && arm_arch >= 8) {
          return true;
        }
      }
    }
    return false;
  }

  bool BeginSourceFileAction(clang::CompilerInstance& CI
#if LLVM_VERSION_MAJOR < 5
                             ,
                             llvm::StringRef /*Filename*/
#endif
                             ) override
  {
    CI.getPreprocessor().setPredefines(this->UpdatePredefines(CI));
    return true;
  }
};

class CastXMLPrintPreprocessedAction
  : public CastXMLPredefines<clang::PrintPreprocessedAction>
{
public:
  CastXMLPrintPreprocessedAction(Options const& opts)
    : CastXMLPredefines(opts)
  {
  }
};

class CastXMLSyntaxOnlyAction
  : public CastXMLPredefines<clang::SyntaxOnlyAction>
{
  std::unique_ptr<clang::ASTConsumer> CreateASTConsumer(
    clang::CompilerInstance& CI, llvm::StringRef InFile) override
  {
    using llvm::sys::path::filename;
    if (!this->Opts.GccXml && !this->Opts.CastXml) {
      return clang::SyntaxOnlyAction::CreateASTConsumer(CI, InFile);
#ifdef CASTXML_OWNS_OSTREAM
    } else if (std::unique_ptr<llvm::raw_ostream> OS =
                 CI.createDefaultOutputFile(false, filename(InFile), "xml")) {
      return CASTXML_MAKE_UNIQUE<ASTConsumer>(CI, std::move(OS), this->Opts);
#else
    } else if (llvm::raw_ostream* OS =
                 CI.createDefaultOutputFile(false, filename(InFile), "xml")) {
      return CASTXML_MAKE_UNIQUE<ASTConsumer>(CI, *OS, this->Opts);
#endif
    } else {
      return nullptr;
    }
  }

protected:
  bool BeginSourceFileAction(clang::CompilerInstance& CI
#if LLVM_VERSION_MAJOR < 5
                             ,
                             llvm::StringRef Filename
#endif
                             ) override
  {
    this->CastXMLPredefines::BeginSourceFileAction(CI
#if LLVM_VERSION_MAJOR < 5
                                                   ,
                                                   Filename
#endif
    );

    // Tell Clang not to tear down the parser at EOF.
    // We need it in ASTConsumer::HandleTranslationUnit.
    CI.getPreprocessor().enableIncrementalProcessing();

    return true;
  }

public:
  CastXMLSyntaxOnlyAction(Options const& opts)
    : CastXMLPredefines(opts)
  {
  }
};

static clang::FrontendAction* CreateFrontendAction(clang::CompilerInstance* CI,
                                                   Options const& opts)
{
  clang::frontend::ActionKind action =
    CI->getInvocation().getFrontendOpts().ProgramAction;
  switch (action) {
    case clang::frontend::PrintPreprocessedInput:
      return new CastXMLPrintPreprocessedAction(opts);
    case clang::frontend::ParseSyntaxOnly:
      return new CastXMLSyntaxOnlyAction(opts);
    default:
      std::cerr << "error: unsupported action: " << int(action) << "\n";
      return nullptr;
  }
}

static bool isObjC(clang::CompilerInstance* CI)
{
#if LLVM_VERSION_MAJOR >= 8
  return CI->getLangOpts().ObjC;
#else
  return CI->getLangOpts().ObjC1 || CI->getLangOpts().ObjC2;
#endif
}

static bool runClangCI(clang::CompilerInstance* CI, Options const& opts)
{
  // Create a diagnostics engine for this compiler instance.
  CI->createDiagnostics(
#if LLVM_VERSION_MAJOR >= 20
    *llvm::vfs::getRealFileSystem()
#endif
  );
  if (!CI->hasDiagnostics()) {
    return false;
  }

  // Set frontend options we captured directly.
  CI->getFrontendOpts().OutputFile = opts.OutputFile;

  if (opts.GccXml) {
#define MSG(x) "error: '--castxml-gccxml' does not work with " x "\n"
    if (isObjC(CI)) {
      std::cerr << MSG("Objective C");
      return false;
    }
#undef MSG
  }

  if (opts.CastXml) {
#define MSG(x) "error: '--castxml-output=<v>' does not work with " x "\n"
    if (isObjC(CI)) {
      std::cerr << MSG("Objective C");
      return false;
    }
#undef MSG
  }

  // Construct our Clang front-end action.  This dispatches
  // handling of each input file with an action based on the
  // flags provided (e.g. -E to preprocess-only).
  std::unique_ptr<clang::FrontendAction> action(
    CreateFrontendAction(CI, opts));
  if (action) {
    return CI->ExecuteAction(*action);
  } else {
    return false;
  }
}

static llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine>
runClangCreateDiagnostics(const char* const* argBeg, const char* const* argEnd)
{
  llvm::IntrusiveRefCntPtr<clang::DiagnosticOptions> diagOpts(
    new clang::DiagnosticOptions);
  llvm::IntrusiveRefCntPtr<clang::DiagnosticIDs> diagID(
    new clang::DiagnosticIDs());
#if LLVM_VERSION_MAJOR >= 10
  llvm::opt::OptTable const* opts = &clang::driver::getDriverOptTable();
#else
  std::unique_ptr<llvm::opt::OptTable> opts(
    clang::driver::createDriverOptTable());
#endif
  unsigned missingArgIndex, missingArgCount;
#if LLVM_VERSION_MAJOR > 3 ||                                                 \
  LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR >= 7
  llvm::opt::InputArgList args(opts->ParseArgs(
#  if LLVM_VERSION_MAJOR >= 16
    llvm::ArrayRef(argBeg, argEnd),
#  else
    llvm::makeArrayRef(argBeg, argEnd),
#  endif
    missingArgIndex, missingArgCount));
  clang::ParseDiagnosticArgs(*diagOpts, args);
#else
  std::unique_ptr<llvm::opt::InputArgList> args(
    opts->ParseArgs(argBeg, argEnd, missingArgIndex, missingArgCount));
  clang::ParseDiagnosticArgs(*diagOpts, *args);
#endif
  clang::TextDiagnosticPrinter* diagClient =
    new clang::TextDiagnosticPrinter(llvm::errs(), &*diagOpts);
  llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diags(
    new clang::DiagnosticsEngine(diagID, &*diagOpts, diagClient));
  clang::ProcessWarningOptions(*diags, *diagOpts,
#if LLVM_VERSION_MAJOR >= 20
                               *llvm::vfs::getRealFileSystem(),
#endif
                               /*ReportDiags=*/false);
  return diags;
}

static int runClangImpl(const char* const* argBeg, const char* const* argEnd,
                        Options const& opts)
{
  // Construct a diagnostics engine for use while processing driver options.
  llvm::IntrusiveRefCntPtr<clang::DiagnosticsEngine> diags =
    runClangCreateDiagnostics(argBeg, argEnd);

  // Use the approach in clang::createInvocationFromCommandLine to
  // get system compiler setting arguments from the Driver.
  clang::driver::Driver d("clang", llvm::sys::getDefaultTargetTriple(),
                          *diags);
  if (!llvm::sys::path::is_absolute(d.ResourceDir) ||
      !llvm::sys::fs::is_directory(d.ResourceDir)) {
    d.ResourceDir = getClangResourceDir();
  }
  llvm::SmallVector<const char*, 16> cArgs;
  cArgs.push_back("<clang>");
  cArgs.insert(cArgs.end(), argBeg, argEnd);

  // Tell the driver not to generate any commands past syntax parsing.
  if (opts.PPOnly) {
    cArgs.push_back("-E");
  } else {
    cArgs.push_back("-fsyntax-only");
  }

  // Ask the driver to build the compiler commands for us.
  std::unique_ptr<clang::driver::Compilation> c(d.BuildCompilation(cArgs));
  if (diags->hasErrorOccurred()) {
    return 1;
  }

  // For '-###' just print the jobs and exit early.
  if (c->getArgs().hasArg(clang::driver::options::OPT__HASH_HASH_HASH)) {
    c->getJobs().Print(llvm::errs(), "\n", true);
    return 0;
  }

  // Reject '-o' with multiple inputs.
  if (!opts.OutputFile.empty() && c->getJobs().size() > 1) {
    diags->Report(clang::diag::err_drv_output_argument_with_multiple_files);
    return 1;
  }

  // Run Clang for each compilation computed by the driver.
  // This should be once per input source file.
  bool result = true;
  for (auto const& job : c->getJobs()) {
    clang::driver::Command const* cmd =
      llvm::dyn_cast<clang::driver::Command>(&job);
    if (cmd && strcmp(cmd->getCreator().getName(), "clang") == 0) {
      // Invoke Clang with this set of arguments.
      std::unique_ptr<clang::CompilerInstance> CI(
        new clang::CompilerInstance());
      const char* const* cmdArgBeg = cmd->getArguments().data();
      const char* const* cmdArgEnd = cmdArgBeg + cmd->getArguments().size();
      if (clang::CompilerInvocation::CreateFromArgs(
            CI->getInvocation(),
#if LLVM_VERSION_MAJOR >= 16
            llvm::ArrayRef(cmdArgBeg, cmdArgEnd),
#elif LLVM_VERSION_MAJOR >= 10
            llvm::makeArrayRef(cmdArgBeg, cmdArgEnd),
#else
            cmdArgBeg, cmdArgEnd,
#endif
            *diags)) {
        if (diags->hasErrorOccurred()) {
          return 1;
        }
        result = runClangCI(CI.get(), opts) && result;
      } else {
        result = false;
      }
    } else {
      // Skip this unexpected job.
      llvm::SmallString<128> buf;
      llvm::raw_svector_ostream msg(buf);
      job.Print(msg, "\n", true);
      diags->Report(clang::diag::err_fe_expected_clang_command);
      diags->Report(clang::diag::err_fe_expected_compiler_job) << msg.str();
      result = false;
    }
  }
  return result ? 0 : 1;
}

int runClang(const char* const* argBeg, const char* const* argEnd,
             Options const& opts)
{
  llvm::SmallVector<const char*, 32> args(argBeg, argEnd);
  std::string fmsc_version = "-fmsc-version=";
  std::string std_flag = "-std=";

  if (opts.HaveCC) {
    // Configure target to match that of given compiler.
    if (!opts.HaveTarget && !opts.Triple.empty()) {
      args.push_back("-target");
      args.push_back(opts.Triple.c_str());
    }

    // Tell Clang driver not to add its header search paths.
    args.push_back("-nobuiltininc");
    args.push_back("-nostdlibinc");

    // Add header search paths detected from given compiler.
    for (std::vector<Options::Include>::const_iterator
           i = opts.Includes.begin(),
           e = opts.Includes.end();
         i != e; ++i) {
      if (i->Framework) {
        args.push_back("-iframework");
      } else {
        args.push_back("-isystem");
      }
      args.push_back(i->Directory.c_str());
    }

    // Tell Clang not to add its predefines.
    args.push_back("-undef");

    // Configure language options to match given compiler.
    std::string const& pd = opts.Predefines;
    if (pd.find("#define __cpp_sized_deallocation ") != std::string::npos) {
      args.emplace_back("-fsized-deallocation");
    }
    if (pd.find("#define _MSC_EXTENSIONS ") != pd.npos) {
      args.push_back("-fms-extensions");
    }
    if (const char* d = strstr(pd.c_str(), "#define _MSC_VER ")) {
      args.push_back("-fms-compatibility");
      // Extract the _MSC_VER value to give to -fmsc-version=.
      d += 17;
      if (const char* e = strchr(d, '\n')) {
        if (*(e - 1) == '\r') {
          --e;
        }
        std::string const msc_ver_str(d, e - d);
        fmsc_version += msc_ver_str;
        args.push_back(fmsc_version.c_str());

        if (!opts.HaveStd) {
          if (pd.find("#define __cplusplus ") != pd.npos) {
            // Extract the C++ level from _MSC_VER to give to -std=.
            // Note that Clang also does this but old versions of Clang
            // do not know about new versions of MSVC.
            errno = 0;
            long msc_ver = std::strtol(msc_ver_str.c_str(), nullptr, 10);
            if (errno != 0) {
              msc_ver = 1600;
            }
            if (msc_ver >= 1900) {
              long msvc_lang = 0;
              if (const char* l = strstr(pd.c_str(), "#define _MSVC_LANG ")) {
                l += 19;
                if (const char* le = strchr(l, '\n')) {
                  if (*(le - 1) == '\r') {
                    --le;
                  }
                  std::string const msvc_lang_str(l, le - l);
                  msvc_lang = std::strtol(msvc_lang_str.c_str(), nullptr, 10);
                }
              }
              if (msvc_lang >= 202002L) {
#if LLVM_VERSION_MAJOR >= 11
                args.push_back("-std=c++20");
#else
                args.push_back("-std=c++17");
#endif
              } else if (msvc_lang >= 201703L) {
                args.push_back("-std=c++17");
              } else {
                args.push_back("-std=c++14");
              }
            } else if (msc_ver >= 1600) {
              args.push_back("-std=c++11");
            } else {
              args.push_back("-std=c++98");
            }
          } else {
            args.push_back("-std=c89");
          }
        }
      }
    } else if (!opts.HaveStd) {
      // Check for GNU extensions.
      if (pd.find("#define __GNUC__ ") != pd.npos &&
          pd.find("#define __STRICT_ANSI__ ") == pd.npos) {
        std_flag += "gnu";
      } else {
        std_flag += "c";
      }

      if (const char* d = strstr(pd.c_str(), "#define __cplusplus ")) {
        // Extract the C++ level to give to -std=.  We do this above for
        // MSVC because it does not set __cplusplus to standard values.
        d += 20;
        if (const char* e = strchr(d, '\n')) {
          if (*(e - 1) == '\r') {
            --e;
          }

          // Add the standard year.
          std::string const std_date_str(d, e - d);
          errno = 0;
          long std_date = std::strtol(std_date_str.c_str(), nullptr, 10);
          if (errno != 0) {
            std_date = 0;
          }
          std_flag += "++";
          if (std_date >= 202002L) {
#if LLVM_VERSION_MAJOR >= 11
            std_flag += "20";
#elif LLVM_VERSION_MAJOR >= 5
            std_flag += "17";
#else
            std_flag += "1z";
#endif
          } else if (std_date >= 201703L) {
#if LLVM_VERSION_MAJOR >= 5
            std_flag += "17";
#else
            std_flag += "1z";
#endif
          } else if (std_date >= 201406L) {
            std_flag += "1z";
          } else if (std_date >= 201402L) {
            std_flag += "14";
          } else if (std_date >= 201103L) {
            std_flag += "11";
          } else {
            std_flag += "98";
          }
          args.push_back(std_flag.c_str());
        }
      } else if (const char* d =
                   strstr(pd.c_str(), "#define __STDC_VERSION__ ")) {
        // Extract the C standard level.
        d += 25;
        if (const char* e = strchr(d, '\n')) {
          if (*(e - 1) == '\r') {
            --e;
          }
          std::string const std_date_str(d, e - d);
          errno = 0;
          long std_date = std::strtol(std_date_str.c_str(), nullptr, 10);
          if (errno != 0) {
            std_date = 0;
          }
          if (std_date >= 201112L) {
            std_flag += "11";
          } else if (std_date >= 199901L) {
            std_flag += "99";
          } else {
            std_flag += "89";
          }
          args.push_back(std_flag.c_str());
        }
      } else {
        // Assume C 89.
        std_flag += "89";
        args.push_back(std_flag.c_str());
      }
    }
  }

  return runClangImpl(args.data(), args.data() + args.size(), opts);
}
