tools/lld/lld.cpp

//===- tools/lld/lld.cpp - Linker Driver Dispatcher -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the main function of the lld executable. The main
// function is a thin wrapper which dispatches to the platform specific
// driver.
//
// lld is a single executable that contains four different linkers for ELF,
// COFF, WebAssembly and Mach-O. The main function dispatches according to
// argv[0] (i.e. command name). The most common name for each target is shown
// below:
//
//  - ld.lld:    ELF (Unix)
//  - ld64:      Mach-O (macOS)
//  - lld-link:  COFF (Windows)
//  - ld-wasm:   WebAssembly
//
// lld can be invoked as "lld" along with "-flavor" option. This is for
// backward compatibility and not recommended.
//
//===----------------------------------------------------------------------===//

#include "lld/Common/Driver.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Memory.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/CrashRecoveryContext.h"
#include "llvm/Support/LLVMDriver.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/PluginLoader.h"
#include "llvm/Support/Process.h"
#include "llvm/TargetParser/Host.h"
#include "llvm/TargetParser/Triple.h"
#include <cstdlib>
#include <optional>

using namespace lld;
using namespace llvm;
using namespace llvm::sys;

namespace lld {
extern bool inTestOutputDisabled;

// Bypass the crash recovery handler, which is only meant to be used in
// LLD-as-lib scenarios.
int unsafeLldMain(llvm::ArrayRef<const char *> args,
                  llvm::raw_ostream &stdoutOS, llvm::raw_ostream &stderrOS,
                  llvm::ArrayRef<DriverDef> drivers, bool exitEarly);
} // namespace lld

// When in lit tests, tells how many times the LLD tool should re-execute the
// main loop with the same inputs. When not in test, returns a value of 0 which
// signifies that LLD shall not release any memory after execution, to speed up
// process destruction.
static unsigned inTestVerbosity() {
  unsigned v = 0;
  StringRef(getenv("LLD_IN_TEST")).getAsInteger(10, v);
  return v;
}

LLD_HAS_DRIVER(coff)
LLD_HAS_DRIVER(elf)
LLD_HAS_DRIVER(mingw)
LLD_HAS_DRIVER(macho)
LLD_HAS_DRIVER(wasm)

int lld_main(int argc, char **argv, const llvm::ToolContext &) {
  sys::Process::UseANSIEscapeCodes(true);

  if (::getenv("FORCE_LLD_DIAGNOSTICS_CRASH")) {
    llvm::errs()
        << "crashing due to environment variable FORCE_LLD_DIAGNOSTICS_CRASH\n";
    LLVM_BUILTIN_TRAP;
  }

  ArrayRef<const char *> args(argv, argv + argc);

  // Not running in lit tests, just take the shortest codepath with global
  // exception handling and no memory cleanup on exit.
  if (!inTestVerbosity()) {
    int r =
        lld::unsafeLldMain(args, llvm::outs(), llvm::errs(), LLD_ALL_DRIVERS,
                           /*exitEarly=*/true);
    return r;
  }

  std::optional<int> mainRet;
  CrashRecoveryContext::Enable();

  for (unsigned i = inTestVerbosity(); i > 0; --i) {
    // Disable stdout/stderr for all iterations but the last one.
    inTestOutputDisabled = (i != 1);

    // Execute one iteration.
    auto r = lldMain(args, llvm::outs(), llvm::errs(), LLD_ALL_DRIVERS);
    if (!r.canRunAgain)
      exitLld(r.retCode); // Exit now, can't re-execute again.

    if (!mainRet) {
      mainRet = r.retCode;
    } else if (r.retCode != *mainRet) {
      // Exit now, to fail the tests if the result is different between runs.
      return r.retCode;
    }
  }
  return *mainRet;
}