1//===- ArchiveWriter.cpp - ar File Format implementation --------*- C++ -*-===//
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 defines the writeArchive function.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/Object/ArchiveWriter.h"
14#include "llvm/ADT/ArrayRef.h"
15#include "llvm/ADT/StringMap.h"
16#include "llvm/ADT/StringRef.h"
17#include "llvm/BinaryFormat/Magic.h"
18#include "llvm/IR/LLVMContext.h"
19#include "llvm/Object/Archive.h"
20#include "llvm/Object/Error.h"
21#include "llvm/Object/ObjectFile.h"
22#include "llvm/Object/SymbolicFile.h"
23#include "llvm/Support/Alignment.h"
24#include "llvm/Support/EndianStream.h"
25#include "llvm/Support/Errc.h"
26#include "llvm/Support/ErrorHandling.h"
27#include "llvm/Support/Format.h"
28#include "llvm/Support/Path.h"
29#include "llvm/Support/SmallVectorMemoryBuffer.h"
30#include "llvm/Support/ToolOutputFile.h"
31#include "llvm/Support/raw_ostream.h"
32
33#include <map>
34
35#if !defined(_MSC_VER) && !defined(__MINGW32__)
36#include <unistd.h>
37#else
38#include <io.h>
39#endif
40
41using namespace llvm;
42
43NewArchiveMember::NewArchiveMember(MemoryBufferRef BufRef)
44    : Buf(MemoryBuffer::getMemBuffer(BufRef, false)),
45      MemberName(BufRef.getBufferIdentifier()) {}
46
47Expected<NewArchiveMember>
48NewArchiveMember::getOldMember(const object::Archive::Child &OldMember,
49                               bool Deterministic) {
50  Expected<llvm::MemoryBufferRef> BufOrErr = OldMember.getMemoryBufferRef();
51  if (!BufOrErr)
52    return BufOrErr.takeError();
53
54  NewArchiveMember M;
55  M.Buf = MemoryBuffer::getMemBuffer(*BufOrErr, false);
56  M.MemberName = M.Buf->getBufferIdentifier();
57  if (!Deterministic) {
58    auto ModTimeOrErr = OldMember.getLastModified();
59    if (!ModTimeOrErr)
60      return ModTimeOrErr.takeError();
61    M.ModTime = ModTimeOrErr.get();
62    Expected<unsigned> UIDOrErr = OldMember.getUID();
63    if (!UIDOrErr)
64      return UIDOrErr.takeError();
65    M.UID = UIDOrErr.get();
66    Expected<unsigned> GIDOrErr = OldMember.getGID();
67    if (!GIDOrErr)
68      return GIDOrErr.takeError();
69    M.GID = GIDOrErr.get();
70    Expected<sys::fs::perms> AccessModeOrErr = OldMember.getAccessMode();
71    if (!AccessModeOrErr)
72      return AccessModeOrErr.takeError();
73    M.Perms = AccessModeOrErr.get();
74  }
75  return std::move(M);
76}
77
78Expected<NewArchiveMember> NewArchiveMember::getFile(StringRef FileName,
79                                                     bool Deterministic) {
80  sys::fs::file_status Status;
81  auto FDOrErr = sys::fs::openNativeFileForRead(FileName);
82  if (!FDOrErr)
83    return FDOrErr.takeError();
84  sys::fs::file_t FD = *FDOrErr;
85  assert(FD != sys::fs::kInvalidFile);
86
87  if (auto EC = sys::fs::status(FD, Status))
88    return errorCodeToError(EC);
89
90  // Opening a directory doesn't make sense. Let it fail.
91  // Linux cannot open directories with open(2), although
92  // cygwin and *bsd can.
93  if (Status.type() == sys::fs::file_type::directory_file)
94    return errorCodeToError(make_error_code(errc::is_a_directory));
95
96  ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
97      MemoryBuffer::getOpenFile(FD, FileName, Status.getSize(), false);
98  if (!MemberBufferOrErr)
99    return errorCodeToError(MemberBufferOrErr.getError());
100
101  if (auto EC = sys::fs::closeFile(FD))
102    return errorCodeToError(EC);
103
104  NewArchiveMember M;
105  M.Buf = std::move(*MemberBufferOrErr);
106  M.MemberName = M.Buf->getBufferIdentifier();
107  if (!Deterministic) {
108    M.ModTime = std::chrono::time_point_cast<std::chrono::seconds>(
109        Status.getLastModificationTime());
110    M.UID = Status.getUser();
111    M.GID = Status.getGroup();
112    M.Perms = Status.permissions();
113  }
114  return std::move(M);
115}
116
117template <typename T>
118static void printWithSpacePadding(raw_ostream &OS, T Data, unsigned Size) {
119  uint64_t OldPos = OS.tell();
120  OS << Data;
121  unsigned SizeSoFar = OS.tell() - OldPos;
122  assert(SizeSoFar <= Size && "Data doesn't fit in Size");
123  OS.indent(Size - SizeSoFar);
124}
125
126static bool isDarwin(object::Archive::Kind Kind) {
127  return Kind == object::Archive::K_DARWIN ||
128         Kind == object::Archive::K_DARWIN64;
129}
130
131static bool isBSDLike(object::Archive::Kind Kind) {
132  switch (Kind) {
133  case object::Archive::K_GNU:
134  case object::Archive::K_GNU64:
135    return false;
136  case object::Archive::K_BSD:
137  case object::Archive::K_DARWIN:
138  case object::Archive::K_DARWIN64:
139    return true;
140  case object::Archive::K_COFF:
141    break;
142  }
143  llvm_unreachable("not supported for writting");
144}
145
146template <class T>
147static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val) {
148  support::endian::write(Out, Val,
149                         isBSDLike(Kind) ? support::little : support::big);
150}
151
152static void printRestOfMemberHeader(
153    raw_ostream &Out, const sys::TimePoint<std::chrono::seconds> &ModTime,
154    unsigned UID, unsigned GID, unsigned Perms, uint64_t Size) {
155  printWithSpacePadding(Out, sys::toTimeT(ModTime), 12);
156
157  // The format has only 6 chars for uid and gid. Truncate if the provided
158  // values don't fit.
159  printWithSpacePadding(Out, UID % 1000000, 6);
160  printWithSpacePadding(Out, GID % 1000000, 6);
161
162  printWithSpacePadding(Out, format("%o", Perms), 8);
163  printWithSpacePadding(Out, Size, 10);
164  Out << "`\n";
165}
166
167static void
168printGNUSmallMemberHeader(raw_ostream &Out, StringRef Name,
169                          const sys::TimePoint<std::chrono::seconds> &ModTime,
170                          unsigned UID, unsigned GID, unsigned Perms,
171                          uint64_t Size) {
172  printWithSpacePadding(Out, Twine(Name) + "/", 16);
173  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
174}
175
176static void
177printBSDMemberHeader(raw_ostream &Out, uint64_t Pos, StringRef Name,
178                     const sys::TimePoint<std::chrono::seconds> &ModTime,
179                     unsigned UID, unsigned GID, unsigned Perms, uint64_t Size) {
180  uint64_t PosAfterHeader = Pos + 60 + Name.size();
181  // Pad so that even 64 bit object files are aligned.
182  unsigned Pad = offsetToAlignment(PosAfterHeader, Align(8));
183  unsigned NameWithPadding = Name.size() + Pad;
184  printWithSpacePadding(Out, Twine("#1/") + Twine(NameWithPadding), 16);
185  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms,
186                          NameWithPadding + Size);
187  Out << Name;
188  while (Pad--)
189    Out.write(uint8_t(0));
190}
191
192static bool useStringTable(bool Thin, StringRef Name) {
193  return Thin || Name.size() >= 16 || Name.contains('/');
194}
195
196static bool is64BitKind(object::Archive::Kind Kind) {
197  switch (Kind) {
198  case object::Archive::K_GNU:
199  case object::Archive::K_BSD:
200  case object::Archive::K_DARWIN:
201  case object::Archive::K_COFF:
202    return false;
203  case object::Archive::K_DARWIN64:
204  case object::Archive::K_GNU64:
205    return true;
206  }
207  llvm_unreachable("not supported for writting");
208}
209
210static void
211printMemberHeader(raw_ostream &Out, uint64_t Pos, raw_ostream &StringTable,
212                  StringMap<uint64_t> &MemberNames, object::Archive::Kind Kind,
213                  bool Thin, const NewArchiveMember &M,
214                  sys::TimePoint<std::chrono::seconds> ModTime, uint64_t Size) {
215  if (isBSDLike(Kind))
216    return printBSDMemberHeader(Out, Pos, M.MemberName, ModTime, M.UID, M.GID,
217                                M.Perms, Size);
218  if (!useStringTable(Thin, M.MemberName))
219    return printGNUSmallMemberHeader(Out, M.MemberName, ModTime, M.UID, M.GID,
220                                     M.Perms, Size);
221  Out << '/';
222  uint64_t NamePos;
223  if (Thin) {
224    NamePos = StringTable.tell();
225    StringTable << M.MemberName << "/\n";
226  } else {
227    auto Insertion = MemberNames.insert({M.MemberName, uint64_t(0)});
228    if (Insertion.second) {
229      Insertion.first->second = StringTable.tell();
230      StringTable << M.MemberName << "/\n";
231    }
232    NamePos = Insertion.first->second;
233  }
234  printWithSpacePadding(Out, NamePos, 15);
235  printRestOfMemberHeader(Out, ModTime, M.UID, M.GID, M.Perms, Size);
236}
237
238namespace {
239struct MemberData {
240  std::vector<unsigned> Symbols;
241  std::string Header;
242  StringRef Data;
243  StringRef Padding;
244};
245} // namespace
246
247static MemberData computeStringTable(StringRef Names) {
248  unsigned Size = Names.size();
249  unsigned Pad = offsetToAlignment(Size, Align(2));
250  std::string Header;
251  raw_string_ostream Out(Header);
252  printWithSpacePadding(Out, "//", 48);
253  printWithSpacePadding(Out, Size + Pad, 10);
254  Out << "`\n";
255  Out.flush();
256  return {{}, std::move(Header), Names, Pad ? "\n" : ""};
257}
258
259static sys::TimePoint<std::chrono::seconds> now(bool Deterministic) {
260  using namespace std::chrono;
261
262  if (!Deterministic)
263    return time_point_cast<seconds>(system_clock::now());
264  return sys::TimePoint<seconds>();
265}
266
267static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
268  Expected<uint32_t> SymFlagsOrErr = S.getFlags();
269  if (!SymFlagsOrErr)
270    // TODO: Actually report errors helpfully.
271    report_fatal_error(SymFlagsOrErr.takeError());
272  if (*SymFlagsOrErr & object::SymbolRef::SF_FormatSpecific)
273    return false;
274  if (!(*SymFlagsOrErr & object::SymbolRef::SF_Global))
275    return false;
276  if (*SymFlagsOrErr & object::SymbolRef::SF_Undefined)
277    return false;
278  return true;
279}
280
281static void printNBits(raw_ostream &Out, object::Archive::Kind Kind,
282                       uint64_t Val) {
283  if (is64BitKind(Kind))
284    print<uint64_t>(Out, Kind, Val);
285  else
286    print<uint32_t>(Out, Kind, Val);
287}
288
289static uint64_t computeSymbolTableSize(object::Archive::Kind Kind,
290                                       uint64_t NumSyms, uint64_t OffsetSize,
291                                       StringRef StringTable,
292                                       uint32_t *Padding = nullptr) {
293  assert((OffsetSize == 4 || OffsetSize == 8) && "Unsupported OffsetSize");
294  uint64_t Size = OffsetSize; // Number of entries
295  if (isBSDLike(Kind))
296    Size += NumSyms * OffsetSize * 2; // Table
297  else
298    Size += NumSyms * OffsetSize; // Table
299  if (isBSDLike(Kind))
300    Size += OffsetSize; // byte count
301  Size += StringTable.size();
302  // ld64 expects the members to be 8-byte aligned for 64-bit content and at
303  // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
304  // uniformly.
305  // We do this for all bsd formats because it simplifies aligning members.
306  uint32_t Pad = offsetToAlignment(Size, Align(isBSDLike(Kind) ? 8 : 2));
307  Size += Pad;
308  if (Padding)
309    *Padding = Pad;
310  return Size;
311}
312
313static void writeSymbolTableHeader(raw_ostream &Out, object::Archive::Kind Kind,
314                                   bool Deterministic, uint64_t Size) {
315  if (isBSDLike(Kind)) {
316    const char *Name = is64BitKind(Kind) ? "__.SYMDEF_64" : "__.SYMDEF";
317    printBSDMemberHeader(Out, Out.tell(), Name, now(Deterministic), 0, 0, 0,
318                         Size);
319  } else {
320    const char *Name = is64BitKind(Kind) ? "/SYM64" : "";
321    printGNUSmallMemberHeader(Out, Name, now(Deterministic), 0, 0, 0, Size);
322  }
323}
324
325static void writeSymbolTable(raw_ostream &Out, object::Archive::Kind Kind,
326                             bool Deterministic, ArrayRef<MemberData> Members,
327                             StringRef StringTable) {
328  // We don't write a symbol table on an archive with no members -- except on
329  // Darwin, where the linker will abort unless the archive has a symbol table.
330  if (StringTable.empty() && !isDarwin(Kind))
331    return;
332
333  unsigned NumSyms = 0;
334  for (const MemberData &M : Members)
335    NumSyms += M.Symbols.size();
336
337  uint64_t OffsetSize = is64BitKind(Kind) ? 8 : 4;
338  uint32_t Pad;
339  uint64_t Size = computeSymbolTableSize(Kind, NumSyms, OffsetSize, StringTable, &Pad);
340  writeSymbolTableHeader(Out, Kind, Deterministic, Size);
341
342  uint64_t Pos = Out.tell() + Size;
343
344  if (isBSDLike(Kind))
345    printNBits(Out, Kind, NumSyms * 2 * OffsetSize);
346  else
347    printNBits(Out, Kind, NumSyms);
348
349  for (const MemberData &M : Members) {
350    for (unsigned StringOffset : M.Symbols) {
351      if (isBSDLike(Kind))
352        printNBits(Out, Kind, StringOffset);
353      printNBits(Out, Kind, Pos); // member offset
354    }
355    Pos += M.Header.size() + M.Data.size() + M.Padding.size();
356  }
357
358  if (isBSDLike(Kind))
359    // byte count of the string table
360    printNBits(Out, Kind, StringTable.size());
361  Out << StringTable;
362
363  while (Pad--)
364    Out.write(uint8_t(0));
365}
366
367static Expected<std::vector<unsigned>>
368getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
369  std::vector<unsigned> Ret;
370
371  // In the scenario when LLVMContext is populated SymbolicFile will contain a
372  // reference to it, thus SymbolicFile should be destroyed first.
373  LLVMContext Context;
374  std::unique_ptr<object::SymbolicFile> Obj;
375
376  const file_magic Type = identify_magic(Buf.getBuffer());
377  // Treat unsupported file types as having no symbols.
378  if (!object::SymbolicFile::isSymbolicFile(Type, &Context))
379    return Ret;
380  if (Type == file_magic::bitcode) {
381    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
382        Buf, file_magic::bitcode, &Context);
383    if (!ObjOrErr)
384      return ObjOrErr.takeError();
385    Obj = std::move(*ObjOrErr);
386  } else {
387    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(Buf);
388    if (!ObjOrErr)
389      return ObjOrErr.takeError();
390    Obj = std::move(*ObjOrErr);
391  }
392
393  HasObject = true;
394  for (const object::BasicSymbolRef &S : Obj->symbols()) {
395    if (!isArchiveSymbol(S))
396      continue;
397    Ret.push_back(SymNames.tell());
398    if (Error E = S.printName(SymNames))
399      return std::move(E);
400    SymNames << '\0';
401  }
402  return Ret;
403}
404
405static Expected<std::vector<MemberData>>
406computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
407                  object::Archive::Kind Kind, bool Thin, bool Deterministic,
408                  bool NeedSymbols, ArrayRef<NewArchiveMember> NewMembers) {
409  static char PaddingData[8] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'};
410
411  // This ignores the symbol table, but we only need the value mod 8 and the
412  // symbol table is aligned to be a multiple of 8 bytes
413  uint64_t Pos = 0;
414
415  std::vector<MemberData> Ret;
416  bool HasObject = false;
417
418  // Deduplicate long member names in the string table and reuse earlier name
419  // offsets. This especially saves space for COFF Import libraries where all
420  // members have the same name.
421  StringMap<uint64_t> MemberNames;
422
423  // UniqueTimestamps is a special case to improve debugging on Darwin:
424  //
425  // The Darwin linker does not link debug info into the final
426  // binary. Instead, it emits entries of type N_OSO in in the output
427  // binary's symbol table, containing references to the linked-in
428  // object files. Using that reference, the debugger can read the
429  // debug data directly from the object files. Alternatively, an
430  // invocation of 'dsymutil' will link the debug data from the object
431  // files into a dSYM bundle, which can be loaded by the debugger,
432  // instead of the object files.
433  //
434  // For an object file, the N_OSO entries contain the absolute path
435  // path to the file, and the file's timestamp. For an object
436  // included in an archive, the path is formatted like
437  // "/absolute/path/to/archive.a(member.o)", and the timestamp is the
438  // archive member's timestamp, rather than the archive's timestamp.
439  //
440  // However, this doesn't always uniquely identify an object within
441  // an archive -- an archive file can have multiple entries with the
442  // same filename. (This will happen commonly if the original object
443  // files started in different directories.) The only way they get
444  // distinguished, then, is via the timestamp. But this process is
445  // unable to find the correct object file in the archive when there
446  // are two files of the same name and timestamp.
447  //
448  // Additionally, timestamp==0 is treated specially, and causes the
449  // timestamp to be ignored as a match criteria.
450  //
451  // That will "usually" work out okay when creating an archive not in
452  // deterministic timestamp mode, because the objects will probably
453  // have been created at different timestamps.
454  //
455  // To ameliorate this problem, in deterministic archive mode (which
456  // is the default), on Darwin we will emit a unique non-zero
457  // timestamp for each entry with a duplicated name. This is still
458  // deterministic: the only thing affecting that timestamp is the
459  // order of the files in the resultant archive.
460  //
461  // See also the functions that handle the lookup:
462  // in lldb: ObjectContainerBSDArchive::Archive::FindObject()
463  // in llvm/tools/dsymutil: BinaryHolder::GetArchiveMemberBuffers().
464  bool UniqueTimestamps = Deterministic && isDarwin(Kind);
465  std::map<StringRef, unsigned> FilenameCount;
466  if (UniqueTimestamps) {
467    for (const NewArchiveMember &M : NewMembers)
468      FilenameCount[M.MemberName]++;
469    for (auto &Entry : FilenameCount)
470      Entry.second = Entry.second > 1 ? 1 : 0;
471  }
472
473  for (const NewArchiveMember &M : NewMembers) {
474    std::string Header;
475    raw_string_ostream Out(Header);
476
477    MemoryBufferRef Buf = M.Buf->getMemBufferRef();
478    StringRef Data = Thin ? "" : Buf.getBuffer();
479
480    // ld64 expects the members to be 8-byte aligned for 64-bit content and at
481    // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
482    // uniformly.  This matches the behaviour with cctools and ensures that ld64
483    // is happy with archives that we generate.
484    unsigned MemberPadding =
485        isDarwin(Kind) ? offsetToAlignment(Data.size(), Align(8)) : 0;
486    unsigned TailPadding =
487        offsetToAlignment(Data.size() + MemberPadding, Align(2));
488    StringRef Padding = StringRef(PaddingData, MemberPadding + TailPadding);
489
490    sys::TimePoint<std::chrono::seconds> ModTime;
491    if (UniqueTimestamps)
492      // Increment timestamp for each file of a given name.
493      ModTime = sys::toTimePoint(FilenameCount[M.MemberName]++);
494    else
495      ModTime = M.ModTime;
496
497    uint64_t Size = Buf.getBufferSize() + MemberPadding;
498    if (Size > object::Archive::MaxMemberSize) {
499      std::string StringMsg =
500          "File " + M.MemberName.str() + " exceeds size limit";
501      return make_error<object::GenericBinaryError>(
502          std::move(StringMsg), object::object_error::parse_failed);
503    }
504
505    printMemberHeader(Out, Pos, StringTable, MemberNames, Kind, Thin, M,
506                      ModTime, Size);
507    Out.flush();
508
509    std::vector<unsigned> Symbols;
510    if (NeedSymbols) {
511      Expected<std::vector<unsigned>> SymbolsOrErr =
512          getSymbols(Buf, SymNames, HasObject);
513      if (auto E = SymbolsOrErr.takeError())
514        return std::move(E);
515      Symbols = std::move(*SymbolsOrErr);
516    }
517
518    Pos += Header.size() + Data.size() + Padding.size();
519    Ret.push_back({std::move(Symbols), std::move(Header), Data, Padding});
520  }
521  // If there are no symbols, emit an empty symbol table, to satisfy Solaris
522  // tools, older versions of which expect a symbol table in a non-empty
523  // archive, regardless of whether there are any symbols in it.
524  if (HasObject && SymNames.tell() == 0)
525    SymNames << '\0' << '\0' << '\0';
526  return Ret;
527}
528
529namespace llvm {
530
531static ErrorOr<SmallString<128>> canonicalizePath(StringRef P) {
532  SmallString<128> Ret = P;
533  std::error_code Err = sys::fs::make_absolute(Ret);
534  if (Err)
535    return Err;
536  sys::path::remove_dots(Ret, /*removedotdot*/ true);
537  return Ret;
538}
539
540// Compute the relative path from From to To.
541Expected<std::string> computeArchiveRelativePath(StringRef From, StringRef To) {
542  ErrorOr<SmallString<128>> PathToOrErr = canonicalizePath(To);
543  ErrorOr<SmallString<128>> DirFromOrErr = canonicalizePath(From);
544  if (!PathToOrErr || !DirFromOrErr)
545    return errorCodeToError(std::error_code(errno, std::generic_category()));
546
547  const SmallString<128> &PathTo = *PathToOrErr;
548  const SmallString<128> &DirFrom = sys::path::parent_path(*DirFromOrErr);
549
550  // Can't construct a relative path between different roots
551  if (sys::path::root_name(PathTo) != sys::path::root_name(DirFrom))
552    return sys::path::convert_to_slash(PathTo);
553
554  // Skip common prefixes
555  auto FromTo =
556      std::mismatch(sys::path::begin(DirFrom), sys::path::end(DirFrom),
557                    sys::path::begin(PathTo));
558  auto FromI = FromTo.first;
559  auto ToI = FromTo.second;
560
561  // Construct relative path
562  SmallString<128> Relative;
563  for (auto FromE = sys::path::end(DirFrom); FromI != FromE; ++FromI)
564    sys::path::append(Relative, sys::path::Style::posix, "..");
565
566  for (auto ToE = sys::path::end(PathTo); ToI != ToE; ++ToI)
567    sys::path::append(Relative, sys::path::Style::posix, *ToI);
568
569  return std::string(Relative.str());
570}
571
572static Error writeArchiveToStream(raw_ostream &Out,
573                                  ArrayRef<NewArchiveMember> NewMembers,
574                                  bool WriteSymtab, object::Archive::Kind Kind,
575                                  bool Deterministic, bool Thin) {
576  assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
577
578  SmallString<0> SymNamesBuf;
579  raw_svector_ostream SymNames(SymNamesBuf);
580  SmallString<0> StringTableBuf;
581  raw_svector_ostream StringTable(StringTableBuf);
582
583  Expected<std::vector<MemberData>> DataOrErr =
584      computeMemberData(StringTable, SymNames, Kind, Thin, Deterministic,
585                        WriteSymtab, NewMembers);
586  if (Error E = DataOrErr.takeError())
587    return E;
588  std::vector<MemberData> &Data = *DataOrErr;
589
590  if (!StringTableBuf.empty())
591    Data.insert(Data.begin(), computeStringTable(StringTableBuf));
592
593  // We would like to detect if we need to switch to a 64-bit symbol table.
594  if (WriteSymtab) {
595    uint64_t MaxOffset = 8; // For the file signature.
596    uint64_t LastOffset = MaxOffset;
597    uint64_t NumSyms = 0;
598    for (const auto &M : Data) {
599      // Record the start of the member's offset
600      LastOffset = MaxOffset;
601      // Account for the size of each part associated with the member.
602      MaxOffset += M.Header.size() + M.Data.size() + M.Padding.size();
603      NumSyms += M.Symbols.size();
604    }
605
606    // We assume 32-bit offsets to see if 32-bit symbols are possible or not.
607    uint64_t SymtabSize = computeSymbolTableSize(Kind, NumSyms, 4, SymNamesBuf);
608    auto computeSymbolTableHeaderSize =
609        [=] {
610          SmallString<0> TmpBuf;
611          raw_svector_ostream Tmp(TmpBuf);
612          writeSymbolTableHeader(Tmp, Kind, Deterministic, SymtabSize);
613          return TmpBuf.size();
614        };
615    LastOffset += computeSymbolTableHeaderSize() + SymtabSize;
616
617    // The SYM64 format is used when an archive's member offsets are larger than
618    // 32-bits can hold. The need for this shift in format is detected by
619    // writeArchive. To test this we need to generate a file with a member that
620    // has an offset larger than 32-bits but this demands a very slow test. To
621    // speed the test up we use this environment variable to pretend like the
622    // cutoff happens before 32-bits and instead happens at some much smaller
623    // value.
624    uint64_t Sym64Threshold = 1ULL << 32;
625    const char *Sym64Env = std::getenv("SYM64_THRESHOLD");
626    if (Sym64Env)
627      StringRef(Sym64Env).getAsInteger(10, Sym64Threshold);
628
629    // If LastOffset isn't going to fit in a 32-bit varible we need to switch
630    // to 64-bit. Note that the file can be larger than 4GB as long as the last
631    // member starts before the 4GB offset.
632    if (LastOffset >= Sym64Threshold) {
633      if (Kind == object::Archive::K_DARWIN)
634        Kind = object::Archive::K_DARWIN64;
635      else
636        Kind = object::Archive::K_GNU64;
637    }
638  }
639
640  if (Thin)
641    Out << "!<thin>\n";
642  else
643    Out << "!<arch>\n";
644
645  if (WriteSymtab)
646    writeSymbolTable(Out, Kind, Deterministic, Data, SymNamesBuf);
647
648  for (const MemberData &M : Data)
649    Out << M.Header << M.Data << M.Padding;
650
651  Out.flush();
652  return Error::success();
653}
654
655Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
656                   bool WriteSymtab, object::Archive::Kind Kind,
657                   bool Deterministic, bool Thin,
658                   std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
659  Expected<sys::fs::TempFile> Temp =
660      sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
661  if (!Temp)
662    return Temp.takeError();
663  raw_fd_ostream Out(Temp->FD, false);
664
665  if (Error E = writeArchiveToStream(Out, NewMembers, WriteSymtab, Kind,
666                                     Deterministic, Thin)) {
667    if (Error DiscardError = Temp->discard())
668      return joinErrors(std::move(E), std::move(DiscardError));
669    return E;
670  }
671
672  // At this point, we no longer need whatever backing memory
673  // was used to generate the NewMembers. On Windows, this buffer
674  // could be a mapped view of the file we want to replace (if
675  // we're updating an existing archive, say). In that case, the
676  // rename would still succeed, but it would leave behind a
677  // temporary file (actually the original file renamed) because
678  // a file cannot be deleted while there's a handle open on it,
679  // only renamed. So by freeing this buffer, this ensures that
680  // the last open handle on the destination file, if any, is
681  // closed before we attempt to rename.
682  OldArchiveBuf.reset();
683
684  return Temp->keep(ArcName);
685}
686
687Expected<std::unique_ptr<MemoryBuffer>>
688writeArchiveToBuffer(ArrayRef<NewArchiveMember> NewMembers, bool WriteSymtab,
689                     object::Archive::Kind Kind, bool Deterministic,
690                     bool Thin) {
691  SmallVector<char, 0> ArchiveBufferVector;
692  raw_svector_ostream ArchiveStream(ArchiveBufferVector);
693
694  if (Error E = writeArchiveToStream(ArchiveStream, NewMembers, WriteSymtab,
695                                     Kind, Deterministic, Thin))
696    return std::move(E);
697
698  return std::make_unique<SmallVectorMemoryBuffer>(
699      std::move(ArchiveBufferVector));
700}
701
702} // namespace llvm
703