1 //===- tools/lld/lld.cpp - Linker Driver Dispatcher -----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains the main function of the lld executable. The main
10 // function is a thin wrapper which dispatches to the platform specific
11 // driver.
12 //
13 // lld is a single executable that contains four different linkers for ELF,
14 // COFF, WebAssembly and Mach-O. The main function dispatches according to
15 // argv[0] (i.e. command name). The most common name for each target is shown
16 // below:
17 //
18 //  - ld.lld:    ELF (Unix)
19 //  - ld64:      Mach-O (macOS)
20 //  - lld-link:  COFF (Windows)
21 //  - ld-wasm:   WebAssembly
22 //
23 // lld can be invoked as "lld" along with "-flavor" option. This is for
24 // backward compatibility and not recommended.
25 //
26 //===----------------------------------------------------------------------===//
27 
28 #include "lld/Common/Driver.h"
29 #include "lld/Common/ErrorHandler.h"
30 #include "lld/Common/Memory.h"
31 #include "llvm/ADT/STLExtras.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/ADT/Twine.h"
34 #include "llvm/Support/CommandLine.h"
35 #include "llvm/Support/CrashRecoveryContext.h"
36 #include "llvm/Support/InitLLVM.h"
37 #include "llvm/Support/LLVMDriver.h"
38 #include "llvm/Support/Path.h"
39 #include "llvm/Support/PluginLoader.h"
40 #include "llvm/Support/Process.h"
41 #include "llvm/TargetParser/Host.h"
42 #include "llvm/TargetParser/Triple.h"
43 #include <cstdlib>
44 #include <optional>
45 
46 using namespace lld;
47 using namespace llvm;
48 using namespace llvm::sys;
49 
50 namespace lld {
51 extern bool inTestOutputDisabled;
52 
53 // Bypass the crash recovery handler, which is only meant to be used in
54 // LLD-as-lib scenarios.
55 int unsafeLldMain(llvm::ArrayRef<const char *> args,
56                   llvm::raw_ostream &stdoutOS, llvm::raw_ostream &stderrOS,
57                   llvm::ArrayRef<DriverDef> drivers, bool exitEarly);
58 } // namespace lld
59 
60 // When in lit tests, tells how many times the LLD tool should re-execute the
61 // main loop with the same inputs. When not in test, returns a value of 0 which
62 // signifies that LLD shall not release any memory after execution, to speed up
63 // process destruction.
64 static unsigned inTestVerbosity() {
65   unsigned v = 0;
66   StringRef(getenv("LLD_IN_TEST")).getAsInteger(10, v);
67   return v;
68 }
69 
70 #if 1
71 // On FreeBSD we only build the ELF linker.
72 LLD_HAS_DRIVER(elf)
73 #undef LLD_ALL_DRIVERS
74 #define LLD_ALL_DRIVERS { {lld::Gnu, &lld::elf::link} }
75 #else
76 LLD_HAS_DRIVER(coff)
77 LLD_HAS_DRIVER(elf)
78 LLD_HAS_DRIVER(mingw)
79 LLD_HAS_DRIVER(macho)
80 LLD_HAS_DRIVER(wasm)
81 #endif
82 
83 int lld_main(int argc, char **argv, const llvm::ToolContext &) {
84   InitLLVM x(argc, argv);
85   sys::Process::UseANSIEscapeCodes(true);
86 
87   if (::getenv("FORCE_LLD_DIAGNOSTICS_CRASH")) {
88     llvm::errs()
89         << "crashing due to environment variable FORCE_LLD_DIAGNOSTICS_CRASH\n";
90     LLVM_BUILTIN_TRAP;
91   }
92 
93   ArrayRef<const char *> args(argv, argv + argc);
94 
95   // Not running in lit tests, just take the shortest codepath with global
96   // exception handling and no memory cleanup on exit.
97   if (!inTestVerbosity()) {
98     int r =
99         lld::unsafeLldMain(args, llvm::outs(), llvm::errs(), LLD_ALL_DRIVERS,
100                            /*exitEarly=*/true);
101     return r;
102   }
103 
104   std::optional<int> mainRet;
105   CrashRecoveryContext::Enable();
106 
107   for (unsigned i = inTestVerbosity(); i > 0; --i) {
108     // Disable stdout/stderr for all iterations but the last one.
109     inTestOutputDisabled = (i != 1);
110 
111     // Execute one iteration.
112     auto r = lldMain(args, llvm::outs(), llvm::errs(), LLD_ALL_DRIVERS);
113     if (!r.canRunAgain)
114       exitLld(r.retCode); // Exit now, can't re-execute again.
115 
116     if (!mainRet) {
117       mainRet = r.retCode;
118     } else if (r.retCode != *mainRet) {
119       // Exit now, to fail the tests if the result is different between runs.
120       return r.retCode;
121     }
122   }
123   return *mainRet;
124 }
125