ldc/driver/linker.cpp

//===-- linker.cpp --------------------------------------------------------===//
//
//                         LDC – the LLVM D compiler
//
// This file is distributed under the BSD-style LDC license. See the LICENSE
// file for details.
//
//===----------------------------------------------------------------------===//

#include "driver/linker.h"
#include "mars.h"
#include "module.h"
#include "root.h"
#include "driver/cl_options.h"
#include "driver/exe_path.h"
#include "driver/tool.h"
#include "gen/irstate.h"
#include "gen/llvm.h"
#include "gen/logger.h"
#include "gen/optimizer.h"
#include "gen/programs.h"
#include "llvm/ADT/Triple.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/Linker/Linker.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#if _WIN32
#include "llvm/Support/SystemUtils.h"
#include "llvm/Support/ConvertUTF.h"
#include <Windows.h>
#endif

#include <algorithm>

//////////////////////////////////////////////////////////////////////////////

static llvm::cl::opt<bool> staticFlag(
    "static",
    llvm::cl::desc(
        "Create a statically linked binary, including all system dependencies"),
    llvm::cl::ZeroOrMore);

// used by LDMD
static llvm::cl::opt<bool> createStaticLibInObjdir(
    "create-static-lib-in-objdir",
    llvm::cl::desc("Create static library in -od directory (DMD-compliant)"),
    llvm::cl::ZeroOrMore, llvm::cl::ReallyHidden);

static llvm::cl::opt<std::string> ltoLibrary(
    "flto-binary",
    llvm::cl::desc(
        "Set the path for LLVMgold.so (Unixes) or libLTO.dylib (Darwin)"),
    llvm::cl::value_desc("file"));

//////////////////////////////////////////////////////////////////////////////

static void CreateDirectoryOnDisk(llvm::StringRef fileName) {
  auto dir = llvm::sys::path::parent_path(fileName);
  if (!dir.empty() && !llvm::sys::fs::exists(dir)) {
    if (auto ec = llvm::sys::fs::create_directories(dir)) {
      error(Loc(), "failed to create path to file: %s\n%s", dir.data(),
            ec.message().c_str());
      fatal();
    }
  }
}

//////////////////////////////////////////////////////////////////////////////

static std::string getOutputName(bool const sharedLib) {
  if (global.params.exefile)
    return global.params.exefile;

  // Infer output name from first object file.
  std::string result = global.params.objfiles->dim
                           ? FileName::removeExt((*global.params.objfiles)[0])
                           : "a.out";

  const char *extension = nullptr;
  if (sharedLib) {
    extension = global.dll_ext;
    if (!global.params.targetTriple->isWindowsMSVCEnvironment())
      result = "lib" + result;
  } else if (global.params.targetTriple->isOSWindows()) {
    extension = "exe";
  }

  if (global.params.run) {
    // If `-run` is passed, the executable is temporary and is removed
    // after execution. Make sure the name does not collide with other files
    // from other processes by creating a unique filename.
    llvm::SmallString<128> tempFilename;
    auto EC = llvm::sys::fs::createTemporaryFile(FileName::name(result.c_str()),
                                                 extension ? extension : "",
                                                 tempFilename);
    if (!EC)
      result = tempFilename.str();
  } else {
    if (extension) {
      result += ".";
      result += extension;
    }
  }

  return result;
}

//////////////////////////////////////////////////////////////////////////////
// LTO functionality

namespace {

void addLinkerFlag(std::vector<std::string> &args, const llvm::Twine &flag) {
  args.push_back("-Xlinker");
  args.push_back(flag.str());
}

std::string getLTOGoldPluginPath() {
  if (!ltoLibrary.empty()) {
    if (llvm::sys::fs::exists(ltoLibrary))
      return ltoLibrary;

    error(Loc(), "-flto-binary: file '%s' not found", ltoLibrary.c_str());
    fatal();
  } else {
    std::string searchPaths[] = {
        exe_path::prependLibDir("LLVMgold.so"), "/usr/local/lib/LLVMgold.so",
        "/usr/lib/bfd-plugins/LLVMgold.so",
    };

    // Try all searchPaths and early return upon the first path found.
    for (auto p : searchPaths) {
      if (llvm::sys::fs::exists(p))
        return p;
    }

    error(Loc(), "The LLVMgold.so plugin (needed for LTO) was not found. You "
                 "can specify its path with -flto-binary=<file>.");
    fatal();
  }
}

void addLTOGoldPluginFlags(std::vector<std::string> &args) {
  addLinkerFlag(args, "-plugin");
  addLinkerFlag(args, getLTOGoldPluginPath());

  if (opts::isUsingThinLTO())
    addLinkerFlag(args, "-plugin-opt=thinlto");

  if (!opts::mCPU.empty())
    addLinkerFlag(args, llvm::Twine("-plugin-opt=mcpu=") + opts::mCPU);

  // Use the O-level passed to LDC as the O-level for LTO, but restrict it to
  // the [0, 3] range that can be passed to the linker plugin.
  static char optChars[15] = "-plugin-opt=O0";
  optChars[13] = '0' + std::min<char>(optLevel(), 3);
  addLinkerFlag(args, optChars);

#if LDC_LLVM_VER >= 400
  const llvm::TargetOptions &TO = gTargetMachine->Options;
  if (TO.FunctionSections)
    addLinkerFlag(args, "-plugin-opt=-function-sections");
  if (TO.DataSections)
    addLinkerFlag(args, "-plugin-opt=-data-sections");
#endif
}

// Returns an empty string when libLTO.dylib was not specified nor found.
std::string getLTOdylibPath() {
  if (!ltoLibrary.empty()) {
    if (llvm::sys::fs::exists(ltoLibrary))
      return ltoLibrary;

    error(Loc(), "-flto-binary: '%s' not found", ltoLibrary.c_str());
    fatal();
  } else {
    std::string searchPath = exe_path::prependLibDir("libLTO.dylib");
    if (llvm::sys::fs::exists(searchPath))
      return searchPath;

    return "";
  }
}

void addDarwinLTOFlags(std::vector<std::string> &args) {
  std::string dylibPath = getLTOdylibPath();
  if (!dylibPath.empty()) {
      args.push_back("-lto_library");
      args.push_back(std::move(dylibPath));
  }
}

/// Adds the required linker flags for LTO builds to args.
void addLTOLinkFlags(std::vector<std::string> &args) {
#if LDC_LLVM_VER >= 309
  if (global.params.targetTriple->isOSLinux() ||
      global.params.targetTriple->isOSFreeBSD() ||
      global.params.targetTriple->isOSNetBSD() ||
      global.params.targetTriple->isOSOpenBSD() ||
      global.params.targetTriple->isOSDragonFly()) {
    // Assume that ld.gold or ld.bfd is used with plugin support.
    addLTOGoldPluginFlags(args);
  } else if (global.params.targetTriple->isOSDarwin()) {
    addDarwinLTOFlags(args);
  }
#endif
}
} // anonymous namespace

//////////////////////////////////////////////////////////////////////////////

namespace {

#if LDC_LLVM_VER >= 306
/// Insert an LLVM bitcode file into the module
void insertBitcodeIntoModule(const char *bcFile, llvm::Module &M,
                             llvm::LLVMContext &Context) {
  Logger::println("*** Linking-in bitcode file %s ***", bcFile);

  llvm::SMDiagnostic Err;
  std::unique_ptr<llvm::Module> loadedModule(
      getLazyIRFileModule(bcFile, Err, Context));
  if (!loadedModule) {
    error(Loc(), "Error when loading LLVM bitcode file: %s", bcFile);
    fatal();
  }
#if LDC_LLVM_VER >= 308
  llvm::Linker(M).linkInModule(std::move(loadedModule));
#else
  llvm::Linker(&M).linkInModule(loadedModule.release());
#endif
}
#endif
}

/// Insert LLVM bitcode files into the module
void insertBitcodeFiles(llvm::Module &M, llvm::LLVMContext &Ctx,
                        Array<const char *> &bitcodeFiles) {
#if LDC_LLVM_VER >= 306
  for (const char *fname : bitcodeFiles) {
    insertBitcodeIntoModule(fname, M, Ctx);
  }
#else
  if (!bitcodeFiles.empty()) {
    error(Loc(),
          "Passing LLVM bitcode files to LDC is not supported for LLVM < 3.6");
    fatal();
  }
#endif
}

//////////////////////////////////////////////////////////////////////////////

static void appendObjectFiles(std::vector<std::string> &args) {
  for (unsigned i = 0; i < global.params.objfiles->dim; i++)
    args.push_back((*global.params.objfiles)[i]);

  if (global.params.targetTriple->isWindowsMSVCEnvironment()) {
    if (global.params.resfile)
      args.push_back(global.params.resfile);
    if (global.params.deffile)
      args.push_back(std::string("/DEF:") + global.params.deffile);
  }
}

//////////////////////////////////////////////////////////////////////////////

static std::string gExePath;

static int linkObjToBinaryGcc(bool sharedLib, bool fullyStatic) {
  Logger::println("*** Linking executable ***");

  // find gcc for linking
  std::string gcc(getGcc());

  // build arguments
  std::vector<std::string> args;

  appendObjectFiles(args);

  // Link with profile-rt library when generating an instrumented binary.
  // profile-rt uses Phobos (MD5 hashing) and therefore must be passed on the
  // commandline before Phobos.
  if (global.params.genInstrProf) {
#if LDC_LLVM_VER >= 308
    if (global.params.targetTriple->isOSLinux()) {
      // For Linux, explicitly define __llvm_profile_runtime as undefined
      // symbol, so that the initialization part of profile-rt is linked in.
      args.push_back(
          ("-Wl,-u," + llvm::getInstrProfRuntimeHookVarName()).str());
    }
#endif
    args.push_back("-lldc-profile-rt");
  }

  // user libs
  for (unsigned i = 0; i < global.params.libfiles->dim; i++)
    args.push_back((*global.params.libfiles)[i]);

  // output filename
  std::string output = getOutputName(sharedLib);

  if (sharedLib) {
    args.push_back("-shared");
  }

  if (fullyStatic) {
    args.push_back("-static");
  }

  args.push_back("-o");
  args.push_back(output);

  // set the global gExePath
  gExePath = output;
  // assert(gExePath.isValid());

  // create path to exe
  CreateDirectoryOnDisk(gExePath);

  // Pass sanitizer arguments to linker. Requires clang.
  if (opts::sanitize == opts::AddressSanitizer) {
    args.push_back("-fsanitize=address");
  }

  if (opts::sanitize == opts::MemorySanitizer) {
    args.push_back("-fsanitize=memory");
  }

  if (opts::sanitize == opts::ThreadSanitizer) {
    args.push_back("-fsanitize=thread");
  }

  // Add LTO link flags before adding the user link switches, such that the user
  // can pass additional options to the LTO plugin.
  if (opts::isUsingLTO())
    addLTOLinkFlags(args);

  // additional linker switches
  for (unsigned i = 0; i < global.params.linkswitches->dim; i++) {
    const char *p = (*global.params.linkswitches)[i];
    // Don't push -l and -L switches using -Xlinker, but pass them indirectly
    // via GCC. This makes sure user-defined paths take precedence over
    // GCC's builtin LIBRARY_PATHs.
    // Options starting with -shared and -static are not handled by
    // the linker and must be passed to the driver.
    auto str = llvm::StringRef(p);
    if (!(str.startswith("-l") || str.startswith("-L") ||
          str.startswith("-shared") || str.startswith("-static"))) {
      args.push_back("-Xlinker");
    }
    args.push_back(p);
  }

  // default libs
  bool addSoname = false;
  switch (global.params.targetTriple->getOS()) {
  case llvm::Triple::Linux:
    addSoname = true;
    // Make sure we don't do --gc-sections when generating a profile-
    // instrumented binary. The runtime relies on magic sections, which
    // would be stripped by gc-section on older version of ld, see bug:
    // https://sourceware.org/bugzilla/show_bug.cgi?id=19161
    if (!opts::disableLinkerStripDead && !global.params.genInstrProf) {
      args.push_back("-Wl,--gc-sections");
    }
    if (global.params.targetTriple->getEnvironment() == llvm::Triple::Android) {
      args.push_back("-ldl");
      args.push_back("-lm");
      break;
    }
    args.push_back("-lrt");
  // fallthrough
  case llvm::Triple::Darwin:
  case llvm::Triple::MacOSX:
    args.push_back("-ldl");
  // fallthrough
  case llvm::Triple::FreeBSD:
  case llvm::Triple::NetBSD:
  case llvm::Triple::OpenBSD:
  case llvm::Triple::DragonFly:
    addSoname = true;
    args.push_back("-lpthread");
    args.push_back("-lm");
    break;

  case llvm::Triple::Solaris:
    args.push_back("-lm");
    args.push_back("-lumem");
    args.push_back("-lsocket");
    args.push_back("-lnsl");
    break;

  default:
    // OS not yet handled, will probably lead to linker errors.
    // FIXME: Win32.
    break;
  }

  if (global.params.targetTriple->isWindowsGNUEnvironment()) {
    // This is really more of a kludge, as linking in the Winsock functions
    // should be handled by the pragma(lib, ...) in std.socket, but it
    // makes LDC behave as expected for now.
    args.push_back("-lws2_32");
  }

  // Only specify -m32/-m64 for architectures where the two variants actually
  // exist (as e.g. the GCC ARM toolchain doesn't recognize the switches).
  // MIPS does not have -m32/-m64 but requires -mabi=.
  if (global.params.targetTriple->get64BitArchVariant().getArch() !=
          llvm::Triple::UnknownArch &&
      global.params.targetTriple->get32BitArchVariant().getArch() !=
          llvm::Triple::UnknownArch) {
    if (global.params.targetTriple->get64BitArchVariant().getArch() ==
            llvm::Triple::mips64 ||
        global.params.targetTriple->get64BitArchVariant().getArch() ==
            llvm::Triple::mips64el) {
      switch (getMipsABI()) {
      case MipsABI::EABI:
        args.push_back("-mabi=eabi");
        break;
      case MipsABI::O32:
        args.push_back("-mabi=32");
        break;
      case MipsABI::N32:
        args.push_back("-mabi=n32");
        break;
      case MipsABI::N64:
        args.push_back("-mabi=64");
        break;
      case MipsABI::Unknown:
        break;
      }
    } else {
      switch (global.params.targetTriple->getArch()) {
      case llvm::Triple::arm:
      case llvm::Triple::armeb:
      case llvm::Triple::aarch64:
      case llvm::Triple::aarch64_be:
#if LDC_LLVM_VER == 305
      case llvm::Triple::arm64:
      case llvm::Triple::arm64_be:
#endif
        break;
      default:
        if (global.params.is64bit) {
          args.push_back("-m64");
        } else {
          args.push_back("-m32");
        }
      }
    }
  }

  if (global.params.dll && addSoname) {
    std::string soname = opts::soname;
    if (!soname.empty()) {
      args.push_back("-Wl,-soname," + soname);
    }
  }

  Logger::println("Linking with: ");
  Stream logstr = Logger::cout();
  for (const auto &arg : args) {
    if (!arg.empty()) {
      logstr << "'" << arg << "'"
             << " ";
    }
  }
  logstr << "\n"; // FIXME where's flush ?

  // try to call linker
  return executeToolAndWait(gcc, args, global.params.verbose);
}

//////////////////////////////////////////////////////////////////////////////

#ifdef _WIN32

namespace windows {
bool needsQuotes(const llvm::StringRef &arg) {
  return // not already quoted
      !(arg.size() > 1 && arg[0] == '"' &&
        arg.back() == '"') && // empty or min 1 space or min 1 double quote
      (arg.empty() || arg.find(' ') != arg.npos || arg.find('"') != arg.npos);
}

size_t countPrecedingBackslashes(const std::string &arg, size_t index) {
  size_t count = 0;

  for (size_t i = index - 1; i >= 0; --i) {
    if (arg[i] != '\\')
      break;
    ++count;
  }

  return count;
}

std::string quoteArg(const std::string &arg) {
  if (!needsQuotes(arg))
    return arg;

  std::string quotedArg;
  quotedArg.reserve(3 + 2 * arg.size()); // worst case

  quotedArg.push_back('"');

  const size_t argLength = arg.length();
  for (size_t i = 0; i < argLength; ++i) {
    if (arg[i] == '"') {
      // Escape all preceding backslashes (if any).
      // Note that we *don't* need to escape runs of backslashes that don't
      // precede a double quote! See MSDN:
      // http://msdn.microsoft.com/en-us/library/17w5ykft%28v=vs.85%29.aspx
      quotedArg.append(countPrecedingBackslashes(arg, i), '\\');

      // Escape the double quote.
      quotedArg.push_back('\\');
    }

    quotedArg.push_back(arg[i]);
  }

  // Make sure our final double quote doesn't get escaped by a trailing
  // backslash.
  quotedArg.append(countPrecedingBackslashes(arg, argLength), '\\');
  quotedArg.push_back('"');

  return quotedArg;
}

int executeAndWait(const char *commandLine) {
  STARTUPINFO si;
  ZeroMemory(&si, sizeof(si));
  si.cb = sizeof(si);

  PROCESS_INFORMATION pi;
  ZeroMemory(&pi, sizeof(pi));

  DWORD exitCode;

#if UNICODE
  std::wstring wcommandLine;
  if (!llvm::ConvertUTF8toWide(commandLine, wcommandLine))
    return -3;
  auto cmdline = const_cast<wchar_t *>(wcommandLine.data());
#else
  auto cmdline = const_cast<char *>(commandLine);
#endif
  // according to MSDN, only CreateProcessW (unicode) may modify the passed
  // command line
  if (!CreateProcess(NULL, cmdline, NULL, NULL, TRUE, 0,
                     NULL, NULL, &si, &pi)) {
    exitCode = -1;
  } else {
    if (WaitForSingleObject(pi.hProcess, INFINITE) != 0 ||
        !GetExitCodeProcess(pi.hProcess, &exitCode))
      exitCode = -2;

    CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
  }

  return exitCode;
}
}

int executeMsvcToolAndWait(const std::string &tool,
                           const std::vector<std::string> &args, bool verbose) {
  llvm::SmallString<1024> commandLine; // full command line incl. executable

  // if the VSINSTALLDIR environment variable is NOT set,
  // the MSVC environment needs to be set up
  const bool needMsvcSetup = !getenv("VSINSTALLDIR");
  if (needMsvcSetup) {
    /* <command line> => %ComSpec% /s /c "<batch file> <command line>"
     *
     * cmd.exe /c treats the following string argument (the command)
     * in a very peculiar way if it starts with a double-quote.
     * By adding /s and enclosing the command in extra double-quotes
     * (WITHOUT additionally escaping the command), the command will
     * be parsed properly.
     */

    auto comspecEnv = getenv("ComSpec");
    if (!comspecEnv) {
      warning(Loc(),
              "'ComSpec' environment variable is not set, assuming 'cmd.exe'.");
      comspecEnv = "cmd.exe";
    }
    std::string cmdExecutable = comspecEnv;
    std::string batchFile = exe_path::prependBinDir(
        global.params.targetTriple->isArch64Bit() ? "amd64.bat" : "x86.bat");

    commandLine.append(windows::quoteArg(cmdExecutable));
    commandLine.append(" /s /c \"");
    commandLine.append(windows::quoteArg(batchFile));
    commandLine.push_back(' ');
    commandLine.append(windows::quoteArg(tool));
  } else {
    std::string toolPath = getProgram(tool.c_str());
    commandLine.append(windows::quoteArg(toolPath));
  }

  const size_t commandLineLengthAfterTool = commandLine.size();

  // append (quoted) args
  for (size_t i = 0; i < args.size(); ++i) {
    commandLine.push_back(' ');
    commandLine.append(windows::quoteArg(args[i]));
  }

  const bool useResponseFile = (!args.empty() && commandLine.size() > 2000);
  llvm::SmallString<128> responseFilePath;
  if (useResponseFile) {
    const size_t firstArgIndex = commandLineLengthAfterTool + 1;
    llvm::StringRef content(commandLine.data() + firstArgIndex,
                            commandLine.size() - firstArgIndex);

    if (llvm::sys::fs::createTemporaryFile("ldc_link", "rsp",
                                           responseFilePath) ||
        llvm::sys::writeFileWithEncoding(
            responseFilePath,
            content)) // keep encoding (LLVM assumes UTF-8 input)
    {
      error(Loc(), "cannot write temporary response file for %s", tool.c_str());
      return -1;
    }

    // replace all args by @<responseFilePath>
    std::string responseFileArg = ("@" + responseFilePath).str();
    commandLine.resize(firstArgIndex);
    commandLine.append(windows::quoteArg(responseFileArg));
  }

  if (needMsvcSetup)
    commandLine.push_back('"');

  const char *finalCommandLine = commandLine.c_str();

  if (verbose) {
    fprintf(global.stdmsg, finalCommandLine);
    fprintf(global.stdmsg, "\n");
    fflush(global.stdmsg);
  }

  const int exitCode = windows::executeAndWait(finalCommandLine);

  if (exitCode != 0) {
    commandLine.resize(commandLineLengthAfterTool);
    if (needMsvcSetup)
      commandLine.push_back('"');
    error(Loc(), "`%s` failed with status: %d", commandLine.c_str(), exitCode);
  }

  if (useResponseFile)
    llvm::sys::fs::remove(responseFilePath);

  return exitCode;
}

#else // !_WIN32

int executeMsvcToolAndWait(const std::string &,
                           const std::vector<std::string> &, bool) {
  assert(0);
  return -1;
}

#endif

//////////////////////////////////////////////////////////////////////////////

static int linkObjToBinaryMSVC(bool sharedLib) {
  Logger::println("*** Linking executable ***");

  std::string tool = "link.exe";

  // build arguments
  std::vector<std::string> args;

  args.push_back("/NOLOGO");

  // specify that the image will contain a table of safe exception handlers
  // (32bit only)
  if (!global.params.is64bit) {
    args.push_back("/SAFESEH");
  }

  // because of a LLVM bug, see LDC issue 442
  if (global.params.symdebug) {
    args.push_back("/LARGEADDRESSAWARE:NO");
  } else {
    args.push_back("/LARGEADDRESSAWARE");
  }

  // output debug information
  if (global.params.symdebug) {
    args.push_back("/DEBUG");
  }

  // enable Link-time Code Generation (aka. whole program optimization)
  if (global.params.optimize) {
    args.push_back("/LTCG");
  }

  // remove dead code and fold identical COMDATs
  if (opts::disableLinkerStripDead) {
    args.push_back("/OPT:NOREF");
  } else {
    args.push_back("/OPT:REF");
    args.push_back("/OPT:ICF");
  }

  // specify creation of DLL
  if (sharedLib) {
    args.push_back("/DLL");
  }

  // output filename
  std::string output = getOutputName(sharedLib);

  args.push_back("/OUT:" + output);

  appendObjectFiles(args);

  // Link with profile-rt library when generating an instrumented binary
  // profile-rt depends on Phobos (MD5 hashing).
  if (global.params.genInstrProf) {
    args.push_back("ldc-profile-rt.lib");
    // profile-rt depends on ws2_32 for symbol `gethostname`
    args.push_back("ws2_32.lib");
  }

  // user libs
  for (unsigned i = 0; i < global.params.libfiles->dim; i++)
    args.push_back((*global.params.libfiles)[i]);

  // set the global gExePath
  gExePath = output;
  // assert(gExePath.isValid());

  // create path to exe
  CreateDirectoryOnDisk(gExePath);

  // additional linker switches
  for (unsigned i = 0; i < global.params.linkswitches->dim; i++) {
    std::string str = global.params.linkswitches->data[i];
    if (str.length() > 2) {
      // rewrite common -L and -l switches
      if (str[0] == '-' && str[1] == 'L') {
        str = "/LIBPATH:" + str.substr(2);
      } else if (str[0] == '-' && str[1] == 'l') {
        str = str.substr(2) + ".lib";
      }
    }
    args.push_back(str);
  }

  // default libs
  // TODO check which libaries are necessary
  args.push_back("kernel32.lib");
  args.push_back("user32.lib");
  args.push_back("gdi32.lib");
  args.push_back("winspool.lib");
  args.push_back("shell32.lib"); // required for dmain2.d
  args.push_back("ole32.lib");
  args.push_back("oleaut32.lib");
  args.push_back("uuid.lib");
  args.push_back("comdlg32.lib");
  args.push_back("advapi32.lib");

  Logger::println("Linking with: ");
  Stream logstr = Logger::cout();
  for (const auto &arg : args) {
    if (!arg.empty()) {
      logstr << "'" << arg << "'"
             << " ";
    }
  }
  logstr << "\n"; // FIXME where's flush ?

  // try to call linker
  return executeMsvcToolAndWait(tool, args, global.params.verbose);
}

//////////////////////////////////////////////////////////////////////////////

int linkObjToBinary() {
  if (global.params.targetTriple->isWindowsMSVCEnvironment()) {
    // TODO: Choose dynamic/static MSVCRT version based on staticFlag?
    return linkObjToBinaryMSVC(global.params.dll);
  }

  return linkObjToBinaryGcc(global.params.dll, staticFlag);
}

//////////////////////////////////////////////////////////////////////////////

int createStaticLibrary() {
  Logger::println("*** Creating static library ***");

  const bool isTargetMSVC =
      global.params.targetTriple->isWindowsMSVCEnvironment();

  // find archiver
  std::string tool(isTargetMSVC ? "lib.exe" : getArchiver());

  // build arguments
  std::vector<std::string> args;

  // ask ar to create a new library
  if (!isTargetMSVC) {
    args.push_back("rcs");
  }

  // ask lib to be quiet
  if (isTargetMSVC) {
    args.push_back("/NOLOGO");
  }

  // enable Link-time Code Generation (aka. whole program optimization)
  if (isTargetMSVC && global.params.optimize) {
    args.push_back("/LTCG");
  }

  // output filename
  std::string libName;
  if (global.params.libname) { // explicit
    libName = global.params.libname;
  } else { // infer from first object file
    libName = global.params.objfiles->dim
                  ? FileName::removeExt((*global.params.objfiles)[0])
                  : "a.out";
    libName.push_back('.');
    libName.append(global.lib_ext);
  }
  if (createStaticLibInObjdir && global.params.objdir &&
      !FileName::absolute(libName.c_str())) {
    libName = FileName::combine(global.params.objdir, libName.c_str());
  }

  if (isTargetMSVC) {
    args.push_back("/OUT:" + libName);
  } else {
    args.push_back(libName);
  }

  appendObjectFiles(args);

  // create path to the library
  CreateDirectoryOnDisk(libName);

  // try to call archiver
  int exitCode;
  if (isTargetMSVC) {
    exitCode = executeMsvcToolAndWait(tool, args, global.params.verbose);
  } else {
    exitCode = executeToolAndWait(tool, args, global.params.verbose);
  }
  return exitCode;
}

//////////////////////////////////////////////////////////////////////////////

void deleteExeFile() {
  if (!gExePath.empty() && !llvm::sys::fs::is_directory(gExePath)) {
    llvm::sys::fs::remove(gExePath);
  }
}

//////////////////////////////////////////////////////////////////////////////

int runProgram() {
  assert(!gExePath.empty());
  // assert(gExePath.isValid());

  // Run executable
  int status =
      executeToolAndWait(gExePath, opts::runargs, global.params.verbose);
  if (status < 0) {
#if defined(_MSC_VER) || defined(__MINGW32__)
    error(Loc(), "program received signal %d", -status);
#else
    error(Loc(), "program received signal %d (%s)", -status,
          strsignal(-status));
#endif
    return -status;
  }
  return status;
}