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//===- tools/lld/lld.cpp - Linker Driver Dispatcher -----------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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 "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Twine.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 bool isPETarget(const std::vector<const char *> &V) {
for (auto It = V.begin(); It + 1 != V.end(); ++It) {
if (StringRef(*It) != "-m")
continue;
StringRef S = *(It + 1);
return S == "i386pe" || S == "i386pep" || S == "thumb2pe" || S == "arm64pe";
}
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-lld"
" (WebAssembly) instead");
}
}