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//===- 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/Memory.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/Path.h"
#include <cstdlib>
using namespace lld;
using namespace llvm;
using namespace llvm::sys;
enum Flavor {
Invalid,
Gnu, // -flavor gnu
WinLink, // -flavor link
Darwin, // -flavor darwin
Wasm, // -flavor wasm
};
LLVM_ATTRIBUTE_NORETURN static void die(const Twine &s) {
errs() << s << "\n";
exit(1);
}
static Flavor getFlavor(StringRef s) {
return StringSwitch<Flavor>(s)
.CasesLower("ld", "ld.lld", "gnu", Gnu)
.CasesLower("wasm", "ld-wasm", Wasm)
.CaseLower("link", WinLink)
.CasesLower("ld64", "ld64.lld", "darwin", Darwin)
.Default(Invalid);
}
static cl::TokenizerCallback getDefaultQuotingStyle() {
if (Triple(sys::getProcessTriple()).getOS() == Triple::Win32)
return cl::TokenizeWindowsCommandLine;
return cl::TokenizeGNUCommandLine;
}
static bool isPETargetName(StringRef s) {
return s == "i386pe" || s == "i386pep" || s == "thumb2pe" || s == "arm64pe";
}
static bool isPETarget(std::vector<const char *> &v) {
for (auto it = v.begin(); it + 1 != v.end(); ++it) {
if (StringRef(*it) != "-m")
continue;
return isPETargetName(*(it + 1));
}
// Expand response files (arguments in the form of @<filename>)
// to allow detecting the -m argument from arguments in them.
SmallVector<const char *, 256> expandedArgs(v.data(), v.data() + v.size());
cl::ExpandResponseFiles(saver, getDefaultQuotingStyle(), expandedArgs);
for (auto it = expandedArgs.begin(); it + 1 != expandedArgs.end(); ++it) {
if (StringRef(*it) != "-m")
continue;
return isPETargetName(*(it + 1));
}
return false;
}
static Flavor parseProgname(StringRef progname) {
#if __APPLE__
// Use Darwin driver for "ld" on Darwin.
if (progname == "ld")
return Darwin;
#endif
#if LLVM_ON_UNIX
// Use GNU driver for "ld" on other Unix-like system.
if (progname == "ld")
return Gnu;
#endif
// Progname may be something like "lld-gnu". Parse it.
SmallVector<StringRef, 3> v;
progname.split(v, "-");
for (StringRef s : v)
if (Flavor f = getFlavor(s))
return f;
return Invalid;
}
static Flavor parseFlavor(std::vector<const char *> &v) {
// Parse -flavor option.
if (v.size() > 1 && v[1] == StringRef("-flavor")) {
if (v.size() <= 2)
die("missing arg value for '-flavor'");
Flavor f = getFlavor(v[2]);
if (f == Invalid)
die("Unknown flavor: " + StringRef(v[2]));
v.erase(v.begin() + 1, v.begin() + 3);
return f;
}
// Deduct the flavor from argv[0].
StringRef arg0 = path::filename(v[0]);
if (arg0.endswith_lower(".exe"))
arg0 = arg0.drop_back(4);
return parseProgname(arg0);
}
// If this function returns true, lld calls _exit() so that it quickly
// exits without invoking destructors of globally allocated objects.
//
// We don't want to do that if we are running tests though, because
// doing that breaks leak sanitizer. So, lit sets this environment variable,
// and we use it to detect whether we are running tests or not.
static bool canExitEarly() { return StringRef(getenv("LLD_IN_TEST")) != "1"; }
/// Universal linker main(). This linker emulates the gnu, darwin, or
/// windows linker based on the argv[0] or -flavor option.
int main(int argc, const char **argv) {
InitLLVM x(argc, argv);
std::vector<const char *> args(argv, argv + argc);
switch (parseFlavor(args)) {
case Gnu:
if (isPETarget(args))
return !mingw::link(args);
return !elf::link(args, canExitEarly());
case WinLink:
return !coff::link(args, canExitEarly());
case Darwin:
return !mach_o::link(args, canExitEarly());
case Wasm:
return !wasm::link(args, canExitEarly());
default:
die("lld is a generic driver.\n"
"Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld"
" (WebAssembly) instead");
}
}
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