1 //===- DriverUtils.cpp ----------------------------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains utility functions for the driver. Because there
11 // are so many small functions, we created this separate file to make
12 // Driver.cpp less cluttered.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "Config.h"
17 #include "Driver.h"
18 #include "Symbols.h"
19 #include "lld/Common/ErrorHandler.h"
20 #include "lld/Common/Memory.h"
21 #include "llvm/ADT/Optional.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include "llvm/BinaryFormat/COFF.h"
24 #include "llvm/Object/COFF.h"
25 #include "llvm/Object/WindowsResource.h"
26 #include "llvm/Option/Arg.h"
27 #include "llvm/Option/ArgList.h"
28 #include "llvm/Option/Option.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/FileUtilities.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/Support/Process.h"
33 #include "llvm/Support/Program.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/WindowsManifest/WindowsManifestMerger.h"
36 #include <memory>
37 
38 using namespace llvm::COFF;
39 using namespace llvm;
40 using llvm::sys::Process;
41 
42 namespace lld {
43 namespace coff {
44 namespace {
45 
46 const uint16_t SUBLANG_ENGLISH_US = 0x0409;
47 const uint16_t RT_MANIFEST = 24;
48 
49 class Executor {
50 public:
51   explicit Executor(StringRef S) : Prog(Saver.save(S)) {}
52   void add(StringRef S) { Args.push_back(Saver.save(S)); }
53   void add(std::string &S) { Args.push_back(Saver.save(S)); }
54   void add(Twine S) { Args.push_back(Saver.save(S)); }
55   void add(const char *S) { Args.push_back(Saver.save(S)); }
56 
57   void run() {
58     ErrorOr<std::string> ExeOrErr = sys::findProgramByName(Prog);
59     if (auto EC = ExeOrErr.getError())
60       fatal("unable to find " + Prog + " in PATH: " + EC.message());
61     StringRef Exe = Saver.save(*ExeOrErr);
62     Args.insert(Args.begin(), Exe);
63 
64     std::vector<const char *> Vec;
65     for (StringRef S : Args)
66       Vec.push_back(S.data());
67     Vec.push_back(nullptr);
68 
69     if (sys::ExecuteAndWait(Args[0], Vec.data()) != 0)
70       fatal("ExecuteAndWait failed: " +
71             llvm::join(Args.begin(), Args.end(), " "));
72   }
73 
74 private:
75   StringRef Prog;
76   std::vector<StringRef> Args;
77 };
78 
79 } // anonymous namespace
80 
81 // Returns /machine's value.
82 MachineTypes getMachineType(StringRef S) {
83   MachineTypes MT = StringSwitch<MachineTypes>(S.lower())
84                         .Cases("x64", "amd64", AMD64)
85                         .Cases("x86", "i386", I386)
86                         .Case("arm", ARMNT)
87                         .Case("arm64", ARM64)
88                         .Default(IMAGE_FILE_MACHINE_UNKNOWN);
89   if (MT != IMAGE_FILE_MACHINE_UNKNOWN)
90     return MT;
91   fatal("unknown /machine argument: " + S);
92 }
93 
94 StringRef machineToStr(MachineTypes MT) {
95   switch (MT) {
96   case ARMNT:
97     return "arm";
98   case ARM64:
99     return "arm64";
100   case AMD64:
101     return "x64";
102   case I386:
103     return "x86";
104   default:
105     llvm_unreachable("unknown machine type");
106   }
107 }
108 
109 // Parses a string in the form of "<integer>[,<integer>]".
110 void parseNumbers(StringRef Arg, uint64_t *Addr, uint64_t *Size) {
111   StringRef S1, S2;
112   std::tie(S1, S2) = Arg.split(',');
113   if (S1.getAsInteger(0, *Addr))
114     fatal("invalid number: " + S1);
115   if (Size && !S2.empty() && S2.getAsInteger(0, *Size))
116     fatal("invalid number: " + S2);
117 }
118 
119 // Parses a string in the form of "<integer>[.<integer>]".
120 // If second number is not present, Minor is set to 0.
121 void parseVersion(StringRef Arg, uint32_t *Major, uint32_t *Minor) {
122   StringRef S1, S2;
123   std::tie(S1, S2) = Arg.split('.');
124   if (S1.getAsInteger(0, *Major))
125     fatal("invalid number: " + S1);
126   *Minor = 0;
127   if (!S2.empty() && S2.getAsInteger(0, *Minor))
128     fatal("invalid number: " + S2);
129 }
130 
131 // Parses a string in the form of "<subsystem>[,<integer>[.<integer>]]".
132 void parseSubsystem(StringRef Arg, WindowsSubsystem *Sys, uint32_t *Major,
133                     uint32_t *Minor) {
134   StringRef SysStr, Ver;
135   std::tie(SysStr, Ver) = Arg.split(',');
136   *Sys = StringSwitch<WindowsSubsystem>(SysStr.lower())
137     .Case("boot_application", IMAGE_SUBSYSTEM_WINDOWS_BOOT_APPLICATION)
138     .Case("console", IMAGE_SUBSYSTEM_WINDOWS_CUI)
139     .Case("efi_application", IMAGE_SUBSYSTEM_EFI_APPLICATION)
140     .Case("efi_boot_service_driver", IMAGE_SUBSYSTEM_EFI_BOOT_SERVICE_DRIVER)
141     .Case("efi_rom", IMAGE_SUBSYSTEM_EFI_ROM)
142     .Case("efi_runtime_driver", IMAGE_SUBSYSTEM_EFI_RUNTIME_DRIVER)
143     .Case("native", IMAGE_SUBSYSTEM_NATIVE)
144     .Case("posix", IMAGE_SUBSYSTEM_POSIX_CUI)
145     .Case("windows", IMAGE_SUBSYSTEM_WINDOWS_GUI)
146     .Default(IMAGE_SUBSYSTEM_UNKNOWN);
147   if (*Sys == IMAGE_SUBSYSTEM_UNKNOWN)
148     fatal("unknown subsystem: " + SysStr);
149   if (!Ver.empty())
150     parseVersion(Ver, Major, Minor);
151 }
152 
153 // Parse a string of the form of "<from>=<to>".
154 // Results are directly written to Config.
155 void parseAlternateName(StringRef S) {
156   StringRef From, To;
157   std::tie(From, To) = S.split('=');
158   if (From.empty() || To.empty())
159     fatal("/alternatename: invalid argument: " + S);
160   auto It = Config->AlternateNames.find(From);
161   if (It != Config->AlternateNames.end() && It->second != To)
162     fatal("/alternatename: conflicts: " + S);
163   Config->AlternateNames.insert(It, std::make_pair(From, To));
164 }
165 
166 // Parse a string of the form of "<from>=<to>".
167 // Results are directly written to Config.
168 void parseMerge(StringRef S) {
169   StringRef From, To;
170   std::tie(From, To) = S.split('=');
171   if (From.empty() || To.empty())
172     fatal("/merge: invalid argument: " + S);
173   auto Pair = Config->Merge.insert(std::make_pair(From, To));
174   bool Inserted = Pair.second;
175   if (!Inserted) {
176     StringRef Existing = Pair.first->second;
177     if (Existing != To)
178       warn(S + ": already merged into " + Existing);
179   }
180 }
181 
182 static uint32_t parseSectionAttributes(StringRef S) {
183   uint32_t Ret = 0;
184   for (char C : S.lower()) {
185     switch (C) {
186     case 'd':
187       Ret |= IMAGE_SCN_MEM_DISCARDABLE;
188       break;
189     case 'e':
190       Ret |= IMAGE_SCN_MEM_EXECUTE;
191       break;
192     case 'k':
193       Ret |= IMAGE_SCN_MEM_NOT_CACHED;
194       break;
195     case 'p':
196       Ret |= IMAGE_SCN_MEM_NOT_PAGED;
197       break;
198     case 'r':
199       Ret |= IMAGE_SCN_MEM_READ;
200       break;
201     case 's':
202       Ret |= IMAGE_SCN_MEM_SHARED;
203       break;
204     case 'w':
205       Ret |= IMAGE_SCN_MEM_WRITE;
206       break;
207     default:
208       fatal("/section: invalid argument: " + S);
209     }
210   }
211   return Ret;
212 }
213 
214 // Parses /section option argument.
215 void parseSection(StringRef S) {
216   StringRef Name, Attrs;
217   std::tie(Name, Attrs) = S.split(',');
218   if (Name.empty() || Attrs.empty())
219     fatal("/section: invalid argument: " + S);
220   Config->Section[Name] = parseSectionAttributes(Attrs);
221 }
222 
223 // Parses /aligncomm option argument.
224 void parseAligncomm(StringRef S) {
225   StringRef Name, Align;
226   std::tie(Name, Align) = S.split(',');
227   if (Name.empty() || Align.empty()) {
228     error("/aligncomm: invalid argument: " + S);
229     return;
230   }
231   int V;
232   if (Align.getAsInteger(0, V)) {
233     error("/aligncomm: invalid argument: " + S);
234     return;
235   }
236   Config->AlignComm[Name] = std::max(Config->AlignComm[Name], 1 << V);
237 }
238 
239 // Parses a string in the form of "EMBED[,=<integer>]|NO".
240 // Results are directly written to Config.
241 void parseManifest(StringRef Arg) {
242   if (Arg.equals_lower("no")) {
243     Config->Manifest = Configuration::No;
244     return;
245   }
246   if (!Arg.startswith_lower("embed"))
247     fatal("invalid option " + Arg);
248   Config->Manifest = Configuration::Embed;
249   Arg = Arg.substr(strlen("embed"));
250   if (Arg.empty())
251     return;
252   if (!Arg.startswith_lower(",id="))
253     fatal("invalid option " + Arg);
254   Arg = Arg.substr(strlen(",id="));
255   if (Arg.getAsInteger(0, Config->ManifestID))
256     fatal("invalid option " + Arg);
257 }
258 
259 // Parses a string in the form of "level=<string>|uiAccess=<string>|NO".
260 // Results are directly written to Config.
261 void parseManifestUAC(StringRef Arg) {
262   if (Arg.equals_lower("no")) {
263     Config->ManifestUAC = false;
264     return;
265   }
266   for (;;) {
267     Arg = Arg.ltrim();
268     if (Arg.empty())
269       return;
270     if (Arg.startswith_lower("level=")) {
271       Arg = Arg.substr(strlen("level="));
272       std::tie(Config->ManifestLevel, Arg) = Arg.split(" ");
273       continue;
274     }
275     if (Arg.startswith_lower("uiaccess=")) {
276       Arg = Arg.substr(strlen("uiaccess="));
277       std::tie(Config->ManifestUIAccess, Arg) = Arg.split(" ");
278       continue;
279     }
280     fatal("invalid option " + Arg);
281   }
282 }
283 
284 // An RAII temporary file class that automatically removes a temporary file.
285 namespace {
286 class TemporaryFile {
287 public:
288   TemporaryFile(StringRef Prefix, StringRef Extn, StringRef Contents = "") {
289     SmallString<128> S;
290     if (auto EC = sys::fs::createTemporaryFile("lld-" + Prefix, Extn, S))
291       fatal("cannot create a temporary file: " + EC.message());
292     Path = S.str();
293 
294     if (!Contents.empty()) {
295       std::error_code EC;
296       raw_fd_ostream OS(Path, EC, sys::fs::F_None);
297       if (EC)
298         fatal("failed to open " + Path + ": " + EC.message());
299       OS << Contents;
300     }
301   }
302 
303   TemporaryFile(TemporaryFile &&Obj) {
304     std::swap(Path, Obj.Path);
305   }
306 
307   ~TemporaryFile() {
308     if (Path.empty())
309       return;
310     if (sys::fs::remove(Path))
311       fatal("failed to remove " + Path);
312   }
313 
314   // Returns a memory buffer of this temporary file.
315   // Note that this function does not leave the file open,
316   // so it is safe to remove the file immediately after this function
317   // is called (you cannot remove an opened file on Windows.)
318   std::unique_ptr<MemoryBuffer> getMemoryBuffer() {
319     // IsVolatileSize=true forces MemoryBuffer to not use mmap().
320     return CHECK(MemoryBuffer::getFile(Path, /*FileSize=*/-1,
321                                        /*RequiresNullTerminator=*/false,
322                                        /*IsVolatileSize=*/true),
323                  "could not open " + Path);
324   }
325 
326   std::string Path;
327 };
328 }
329 
330 static std::string createDefaultXml() {
331   std::string Ret;
332   raw_string_ostream OS(Ret);
333 
334   // Emit the XML. Note that we do *not* verify that the XML attributes are
335   // syntactically correct. This is intentional for link.exe compatibility.
336   OS << "<?xml version=\"1.0\" standalone=\"yes\"?>\n"
337      << "<assembly xmlns=\"urn:schemas-microsoft-com:asm.v1\"\n"
338      << "          manifestVersion=\"1.0\">\n";
339   if (Config->ManifestUAC) {
340     OS << "  <trustInfo>\n"
341        << "    <security>\n"
342        << "      <requestedPrivileges>\n"
343        << "         <requestedExecutionLevel level=" << Config->ManifestLevel
344        << " uiAccess=" << Config->ManifestUIAccess << "/>\n"
345        << "      </requestedPrivileges>\n"
346        << "    </security>\n"
347        << "  </trustInfo>\n";
348   }
349   if (!Config->ManifestDependency.empty()) {
350     OS << "  <dependency>\n"
351        << "    <dependentAssembly>\n"
352        << "      <assemblyIdentity " << Config->ManifestDependency << " />\n"
353        << "    </dependentAssembly>\n"
354        << "  </dependency>\n";
355   }
356   OS << "</assembly>\n";
357   return OS.str();
358 }
359 
360 static std::string createManifestXmlWithInternalMt(StringRef DefaultXml) {
361   std::unique_ptr<MemoryBuffer> DefaultXmlCopy =
362       MemoryBuffer::getMemBufferCopy(DefaultXml);
363 
364   windows_manifest::WindowsManifestMerger Merger;
365   if (auto E = Merger.merge(*DefaultXmlCopy.get()))
366     fatal("internal manifest tool failed on default xml: " +
367           toString(std::move(E)));
368 
369   for (StringRef Filename : Config->ManifestInput) {
370     std::unique_ptr<MemoryBuffer> Manifest =
371         check(MemoryBuffer::getFile(Filename));
372     if (auto E = Merger.merge(*Manifest.get()))
373       fatal("internal manifest tool failed on file " + Filename + ": " +
374             toString(std::move(E)));
375   }
376 
377   return Merger.getMergedManifest().get()->getBuffer();
378 }
379 
380 static std::string createManifestXmlWithExternalMt(StringRef DefaultXml) {
381   // Create the default manifest file as a temporary file.
382   TemporaryFile Default("defaultxml", "manifest");
383   std::error_code EC;
384   raw_fd_ostream OS(Default.Path, EC, sys::fs::F_Text);
385   if (EC)
386     fatal("failed to open " + Default.Path + ": " + EC.message());
387   OS << DefaultXml;
388   OS.close();
389 
390   // Merge user-supplied manifests if they are given.  Since libxml2 is not
391   // enabled, we must shell out to Microsoft's mt.exe tool.
392   TemporaryFile User("user", "manifest");
393 
394   Executor E("mt.exe");
395   E.add("/manifest");
396   E.add(Default.Path);
397   for (StringRef Filename : Config->ManifestInput) {
398     E.add("/manifest");
399     E.add(Filename);
400   }
401   E.add("/nologo");
402   E.add("/out:" + StringRef(User.Path));
403   E.run();
404 
405   return CHECK(MemoryBuffer::getFile(User.Path), "could not open " + User.Path)
406       .get()
407       ->getBuffer();
408 }
409 
410 static std::string createManifestXml() {
411   std::string DefaultXml = createDefaultXml();
412   if (Config->ManifestInput.empty())
413     return DefaultXml;
414 
415   if (windows_manifest::isAvailable())
416     return createManifestXmlWithInternalMt(DefaultXml);
417 
418   return createManifestXmlWithExternalMt(DefaultXml);
419 }
420 
421 static std::unique_ptr<WritableMemoryBuffer>
422 createMemoryBufferForManifestRes(size_t ManifestSize) {
423   size_t ResSize = alignTo(
424       object::WIN_RES_MAGIC_SIZE + object::WIN_RES_NULL_ENTRY_SIZE +
425           sizeof(object::WinResHeaderPrefix) + sizeof(object::WinResIDs) +
426           sizeof(object::WinResHeaderSuffix) + ManifestSize,
427       object::WIN_RES_DATA_ALIGNMENT);
428   return WritableMemoryBuffer::getNewMemBuffer(ResSize, Config->OutputFile +
429                                                             ".manifest.res");
430 }
431 
432 static void writeResFileHeader(char *&Buf) {
433   memcpy(Buf, COFF::WinResMagic, sizeof(COFF::WinResMagic));
434   Buf += sizeof(COFF::WinResMagic);
435   memset(Buf, 0, object::WIN_RES_NULL_ENTRY_SIZE);
436   Buf += object::WIN_RES_NULL_ENTRY_SIZE;
437 }
438 
439 static void writeResEntryHeader(char *&Buf, size_t ManifestSize) {
440   // Write the prefix.
441   auto *Prefix = reinterpret_cast<object::WinResHeaderPrefix *>(Buf);
442   Prefix->DataSize = ManifestSize;
443   Prefix->HeaderSize = sizeof(object::WinResHeaderPrefix) +
444                        sizeof(object::WinResIDs) +
445                        sizeof(object::WinResHeaderSuffix);
446   Buf += sizeof(object::WinResHeaderPrefix);
447 
448   // Write the Type/Name IDs.
449   auto *IDs = reinterpret_cast<object::WinResIDs *>(Buf);
450   IDs->setType(RT_MANIFEST);
451   IDs->setName(Config->ManifestID);
452   Buf += sizeof(object::WinResIDs);
453 
454   // Write the suffix.
455   auto *Suffix = reinterpret_cast<object::WinResHeaderSuffix *>(Buf);
456   Suffix->DataVersion = 0;
457   Suffix->MemoryFlags = object::WIN_RES_PURE_MOVEABLE;
458   Suffix->Language = SUBLANG_ENGLISH_US;
459   Suffix->Version = 0;
460   Suffix->Characteristics = 0;
461   Buf += sizeof(object::WinResHeaderSuffix);
462 }
463 
464 // Create a resource file containing a manifest XML.
465 std::unique_ptr<MemoryBuffer> createManifestRes() {
466   std::string Manifest = createManifestXml();
467 
468   std::unique_ptr<WritableMemoryBuffer> Res =
469       createMemoryBufferForManifestRes(Manifest.size());
470 
471   char *Buf = Res->getBufferStart();
472   writeResFileHeader(Buf);
473   writeResEntryHeader(Buf, Manifest.size());
474 
475   // Copy the manifest data into the .res file.
476   std::copy(Manifest.begin(), Manifest.end(), Buf);
477   return std::move(Res);
478 }
479 
480 void createSideBySideManifest() {
481   std::string Path = Config->ManifestFile;
482   if (Path == "")
483     Path = Config->OutputFile + ".manifest";
484   std::error_code EC;
485   raw_fd_ostream Out(Path, EC, sys::fs::F_Text);
486   if (EC)
487     fatal("failed to create manifest: " + EC.message());
488   Out << createManifestXml();
489 }
490 
491 // Parse a string in the form of
492 // "<name>[=<internalname>][,@ordinal[,NONAME]][,DATA][,PRIVATE]"
493 // or "<name>=<dllname>.<name>".
494 // Used for parsing /export arguments.
495 Export parseExport(StringRef Arg) {
496   Export E;
497   StringRef Rest;
498   std::tie(E.Name, Rest) = Arg.split(",");
499   if (E.Name.empty())
500     goto err;
501 
502   if (E.Name.contains('=')) {
503     StringRef X, Y;
504     std::tie(X, Y) = E.Name.split("=");
505 
506     // If "<name>=<dllname>.<name>".
507     if (Y.contains(".")) {
508       E.Name = X;
509       E.ForwardTo = Y;
510       return E;
511     }
512 
513     E.ExtName = X;
514     E.Name = Y;
515     if (E.Name.empty())
516       goto err;
517   }
518 
519   // If "<name>=<internalname>[,@ordinal[,NONAME]][,DATA][,PRIVATE]"
520   while (!Rest.empty()) {
521     StringRef Tok;
522     std::tie(Tok, Rest) = Rest.split(",");
523     if (Tok.equals_lower("noname")) {
524       if (E.Ordinal == 0)
525         goto err;
526       E.Noname = true;
527       continue;
528     }
529     if (Tok.equals_lower("data")) {
530       E.Data = true;
531       continue;
532     }
533     if (Tok.equals_lower("constant")) {
534       E.Constant = true;
535       continue;
536     }
537     if (Tok.equals_lower("private")) {
538       E.Private = true;
539       continue;
540     }
541     if (Tok.startswith("@")) {
542       int32_t Ord;
543       if (Tok.substr(1).getAsInteger(0, Ord))
544         goto err;
545       if (Ord <= 0 || 65535 < Ord)
546         goto err;
547       E.Ordinal = Ord;
548       continue;
549     }
550     goto err;
551   }
552   return E;
553 
554 err:
555   fatal("invalid /export: " + Arg);
556 }
557 
558 static StringRef undecorate(StringRef Sym) {
559   if (Config->Machine != I386)
560     return Sym;
561   return Sym.startswith("_") ? Sym.substr(1) : Sym;
562 }
563 
564 // Performs error checking on all /export arguments.
565 // It also sets ordinals.
566 void fixupExports() {
567   // Symbol ordinals must be unique.
568   std::set<uint16_t> Ords;
569   for (Export &E : Config->Exports) {
570     if (E.Ordinal == 0)
571       continue;
572     if (!Ords.insert(E.Ordinal).second)
573       fatal("duplicate export ordinal: " + E.Name);
574   }
575 
576   for (Export &E : Config->Exports) {
577     Symbol *Sym = E.Sym;
578     if (!E.ForwardTo.empty() || !Sym) {
579       E.SymbolName = E.Name;
580     } else {
581       if (auto *U = dyn_cast<Undefined>(Sym))
582         if (U->WeakAlias)
583           Sym = U->WeakAlias;
584       E.SymbolName = Sym->getName();
585     }
586   }
587 
588   for (Export &E : Config->Exports) {
589     if (!E.ForwardTo.empty()) {
590       E.ExportName = undecorate(E.Name);
591     } else {
592       E.ExportName = undecorate(E.ExtName.empty() ? E.Name : E.ExtName);
593     }
594   }
595 
596   // Uniquefy by name.
597   DenseMap<StringRef, Export *> Map(Config->Exports.size());
598   std::vector<Export> V;
599   for (Export &E : Config->Exports) {
600     auto Pair = Map.insert(std::make_pair(E.ExportName, &E));
601     bool Inserted = Pair.second;
602     if (Inserted) {
603       V.push_back(E);
604       continue;
605     }
606     Export *Existing = Pair.first->second;
607     if (E == *Existing || E.Name != Existing->Name)
608       continue;
609     warn("duplicate /export option: " + E.Name);
610   }
611   Config->Exports = std::move(V);
612 
613   // Sort by name.
614   std::sort(Config->Exports.begin(), Config->Exports.end(),
615             [](const Export &A, const Export &B) {
616               return A.ExportName < B.ExportName;
617             });
618 }
619 
620 void assignExportOrdinals() {
621   // Assign unique ordinals if default (= 0).
622   uint16_t Max = 0;
623   for (Export &E : Config->Exports)
624     Max = std::max(Max, E.Ordinal);
625   for (Export &E : Config->Exports)
626     if (E.Ordinal == 0)
627       E.Ordinal = ++Max;
628 }
629 
630 // Parses a string in the form of "key=value" and check
631 // if value matches previous values for the same key.
632 void checkFailIfMismatch(StringRef Arg) {
633   StringRef K, V;
634   std::tie(K, V) = Arg.split('=');
635   if (K.empty() || V.empty())
636     fatal("/failifmismatch: invalid argument: " + Arg);
637   StringRef Existing = Config->MustMatch[K];
638   if (!Existing.empty() && V != Existing)
639     fatal("/failifmismatch: mismatch detected: " + Existing + " and " + V +
640           " for key " + K);
641   Config->MustMatch[K] = V;
642 }
643 
644 // Convert Windows resource files (.res files) to a .obj file.
645 MemoryBufferRef convertResToCOFF(ArrayRef<MemoryBufferRef> MBs) {
646   object::WindowsResourceParser Parser;
647 
648   for (MemoryBufferRef MB : MBs) {
649     std::unique_ptr<object::Binary> Bin = check(object::createBinary(MB));
650     object::WindowsResource *RF = dyn_cast<object::WindowsResource>(Bin.get());
651     if (!RF)
652       fatal("cannot compile non-resource file as resource");
653     if (auto EC = Parser.parse(RF))
654       fatal("failed to parse .res file: " + toString(std::move(EC)));
655   }
656 
657   Expected<std::unique_ptr<MemoryBuffer>> E =
658       llvm::object::writeWindowsResourceCOFF(Config->Machine, Parser);
659   if (!E)
660     fatal("failed to write .res to COFF: " + toString(E.takeError()));
661 
662   MemoryBufferRef MBRef = **E;
663   make<std::unique_ptr<MemoryBuffer>>(std::move(*E)); // take ownership
664   return MBRef;
665 }
666 
667 // Run MSVC link.exe for given in-memory object files.
668 // Command line options are copied from those given to LLD.
669 // This is for the /msvclto option.
670 void runMSVCLinker(std::string Rsp, ArrayRef<StringRef> Objects) {
671   // Write the in-memory object files to disk.
672   std::vector<TemporaryFile> Temps;
673   for (StringRef S : Objects) {
674     Temps.emplace_back("lto", "obj", S);
675     Rsp += quote(Temps.back().Path) + "\n";
676   }
677 
678   log("link.exe " + Rsp);
679 
680   // Run MSVC link.exe.
681   Temps.emplace_back("lto", "rsp", Rsp);
682   Executor E("link.exe");
683   E.add(Twine("@" + Temps.back().Path));
684   E.run();
685 }
686 
687 // Create OptTable
688 
689 // Create prefix string literals used in Options.td
690 #define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
691 #include "Options.inc"
692 #undef PREFIX
693 
694 // Create table mapping all options defined in Options.td
695 static const llvm::opt::OptTable::Info InfoTable[] = {
696 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12)      \
697   {X1, X2, X10,         X11,         OPT_##ID, llvm::opt::Option::KIND##Class, \
698    X9, X8, OPT_##GROUP, OPT_##ALIAS, X7,       X12},
699 #include "Options.inc"
700 #undef OPTION
701 };
702 
703 COFFOptTable::COFFOptTable() : OptTable(InfoTable, true) {}
704 
705 static cl::TokenizerCallback getQuotingStyle(opt::InputArgList &Args) {
706   if (auto *Arg = Args.getLastArg(OPT_rsp_quoting)) {
707     StringRef S = Arg->getValue();
708     if (S != "windows" && S != "posix")
709       error("invalid response file quoting: " + S);
710     if (S == "windows")
711       return cl::TokenizeWindowsCommandLine;
712     return cl::TokenizeGNUCommandLine;
713   }
714   // The COFF linker always defaults to Windows quoting.
715   return cl::TokenizeWindowsCommandLine;
716 }
717 
718 // Parses a given list of options.
719 opt::InputArgList ArgParser::parse(ArrayRef<const char *> Argv) {
720   // Make InputArgList from string vectors.
721   unsigned MissingIndex;
722   unsigned MissingCount;
723   SmallVector<const char *, 256> Vec(Argv.data(), Argv.data() + Argv.size());
724 
725   // We need to get the quoting style for response files before parsing all
726   // options so we parse here before and ignore all the options but
727   // --rsp-quoting.
728   opt::InputArgList Args = Table.ParseArgs(Vec, MissingIndex, MissingCount);
729 
730   // Expand response files (arguments in the form of @<filename>)
731   // and then parse the argument again.
732   cl::ExpandResponseFiles(Saver, getQuotingStyle(Args), Vec);
733   Args = Table.ParseArgs(Vec, MissingIndex, MissingCount);
734 
735   // Print the real command line if response files are expanded.
736   if (Args.hasArg(OPT_verbose) && Argv.size() != Vec.size()) {
737     std::string Msg = "Command line:";
738     for (const char *S : Vec)
739       Msg += " " + std::string(S);
740     message(Msg);
741   }
742 
743   // Handle /WX early since it converts missing argument warnings to errors.
744   errorHandler().FatalWarnings = Args.hasFlag(OPT_WX, OPT_WX_no, false);
745 
746   if (MissingCount)
747     fatal(Twine(Args.getArgString(MissingIndex)) + ": missing argument");
748   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
749     warn("ignoring unknown argument: " + Arg->getSpelling());
750   return Args;
751 }
752 
753 // Tokenizes and parses a given string as command line in .drective section.
754 // /EXPORT options are processed in fastpath.
755 std::pair<opt::InputArgList, std::vector<StringRef>>
756 ArgParser::parseDirectives(StringRef S) {
757   std::vector<StringRef> Exports;
758   SmallVector<const char *, 16> Rest;
759 
760   for (StringRef Tok : tokenize(S)) {
761     if (Tok.startswith_lower("/export:") || Tok.startswith_lower("-export:"))
762       Exports.push_back(Tok.substr(strlen("/export:")));
763     else
764       Rest.push_back(Tok.data());
765   }
766 
767   // Make InputArgList from unparsed string vectors.
768   unsigned MissingIndex;
769   unsigned MissingCount;
770 
771   opt::InputArgList Args = Table.ParseArgs(Rest, MissingIndex, MissingCount);
772 
773   if (MissingCount)
774     fatal(Twine(Args.getArgString(MissingIndex)) + ": missing argument");
775   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
776     warn("ignoring unknown argument: " + Arg->getSpelling());
777   return {std::move(Args), std::move(Exports)};
778 }
779 
780 // link.exe has an interesting feature. If LINK or _LINK_ environment
781 // variables exist, their contents are handled as command line strings.
782 // So you can pass extra arguments using them.
783 opt::InputArgList ArgParser::parseLINK(std::vector<const char *> Argv) {
784   // Concatenate LINK env and command line arguments, and then parse them.
785   if (Optional<std::string> S = Process::GetEnv("LINK")) {
786     std::vector<const char *> V = tokenize(*S);
787     Argv.insert(Argv.begin(), V.begin(), V.end());
788   }
789   if (Optional<std::string> S = Process::GetEnv("_LINK_")) {
790     std::vector<const char *> V = tokenize(*S);
791     Argv.insert(Argv.begin(), V.begin(), V.end());
792   }
793   return parse(Argv);
794 }
795 
796 std::vector<const char *> ArgParser::tokenize(StringRef S) {
797   SmallVector<const char *, 16> Tokens;
798   cl::TokenizeWindowsCommandLine(S, Saver, Tokens);
799   return std::vector<const char *>(Tokens.begin(), Tokens.end());
800 }
801 
802 void printHelp(const char *Argv0) {
803   COFFOptTable().PrintHelp(outs(), Argv0, "LLVM Linker", false);
804 }
805 
806 } // namespace coff
807 } // namespace lld
808