DWARFDebugLine.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
1//===-- DWARFDebugLine.cpp ------------------------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#include "DWARFDebugLine.h" 11#include "llvm/Support/Dwarf.h" 12#include "llvm/Support/Format.h" 13#include "llvm/Support/Path.h" 14#include "llvm/Support/raw_ostream.h" 15#include <algorithm> 16using namespace llvm; 17using namespace dwarf; 18 19void DWARFDebugLine::Prologue::dump(raw_ostream &OS) const { 20 OS << "Line table prologue:\n" 21 << format(" total_length: 0x%8.8x\n", TotalLength) 22 << format(" version: %u\n", Version) 23 << format(" prologue_length: 0x%8.8x\n", PrologueLength) 24 << format(" min_inst_length: %u\n", MinInstLength) 25 << format(Version >= 4 ? "max_ops_per_inst: %u\n" : "", MaxOpsPerInst) 26 << format(" default_is_stmt: %u\n", DefaultIsStmt) 27 << format(" line_base: %i\n", LineBase) 28 << format(" line_range: %u\n", LineRange) 29 << format(" opcode_base: %u\n", OpcodeBase); 30 31 for (uint32_t i = 0; i < StandardOpcodeLengths.size(); ++i) 32 OS << format("standard_opcode_lengths[%s] = %u\n", LNStandardString(i+1), 33 StandardOpcodeLengths[i]); 34 35 if (!IncludeDirectories.empty()) 36 for (uint32_t i = 0; i < IncludeDirectories.size(); ++i) 37 OS << format("include_directories[%3u] = '", i+1) 38 << IncludeDirectories[i] << "'\n"; 39 40 if (!FileNames.empty()) { 41 OS << " Dir Mod Time File Len File Name\n" 42 << " ---- ---------- ---------- -----------" 43 "----------------\n"; 44 for (uint32_t i = 0; i < FileNames.size(); ++i) { 45 const FileNameEntry& fileEntry = FileNames[i]; 46 OS << format("file_names[%3u] %4" PRIu64 " ", i+1, fileEntry.DirIdx) 47 << format("0x%8.8" PRIx64 " 0x%8.8" PRIx64 " ", 48 fileEntry.ModTime, fileEntry.Length) 49 << fileEntry.Name << '\n'; 50 } 51 } 52} 53 54void DWARFDebugLine::Row::postAppend() { 55 BasicBlock = false; 56 PrologueEnd = false; 57 EpilogueBegin = false; 58} 59 60void DWARFDebugLine::Row::reset(bool default_is_stmt) { 61 Address = 0; 62 Line = 1; 63 Column = 0; 64 File = 1; 65 Isa = 0; 66 Discriminator = 0; 67 IsStmt = default_is_stmt; 68 BasicBlock = false; 69 EndSequence = false; 70 PrologueEnd = false; 71 EpilogueBegin = false; 72} 73 74void DWARFDebugLine::Row::dump(raw_ostream &OS) const { 75 OS << format("0x%16.16" PRIx64 " %6u %6u", Address, Line, Column) 76 << format(" %6u %3u %13u ", File, Isa, Discriminator) 77 << (IsStmt ? " is_stmt" : "") 78 << (BasicBlock ? " basic_block" : "") 79 << (PrologueEnd ? " prologue_end" : "") 80 << (EpilogueBegin ? " epilogue_begin" : "") 81 << (EndSequence ? " end_sequence" : "") 82 << '\n'; 83} 84 85void DWARFDebugLine::LineTable::dump(raw_ostream &OS) const { 86 Prologue.dump(OS); 87 OS << '\n'; 88 89 if (!Rows.empty()) { 90 OS << "Address Line Column File ISA Discriminator Flags\n" 91 << "------------------ ------ ------ ------ --- ------------- " 92 "-------------\n"; 93 for (const Row &R : Rows) { 94 R.dump(OS); 95 } 96 } 97} 98 99DWARFDebugLine::State::~State() {} 100 101void DWARFDebugLine::State::appendRowToMatrix(uint32_t offset) { 102 if (Sequence::Empty) { 103 // Record the beginning of instruction sequence. 104 Sequence::Empty = false; 105 Sequence::LowPC = Address; 106 Sequence::FirstRowIndex = row; 107 } 108 ++row; // Increase the row number. 109 LineTable::appendRow(*this); 110 if (EndSequence) { 111 // Record the end of instruction sequence. 112 Sequence::HighPC = Address; 113 Sequence::LastRowIndex = row; 114 if (Sequence::isValid()) 115 LineTable::appendSequence(*this); 116 Sequence::reset(); 117 } 118 Row::postAppend(); 119} 120 121void DWARFDebugLine::State::finalize() { 122 row = DoneParsingLineTable; 123 if (!Sequence::Empty) { 124 fprintf(stderr, "warning: last sequence in debug line table is not" 125 "terminated!\n"); 126 } 127 // Sort all sequences so that address lookup will work faster. 128 if (!Sequences.empty()) { 129 std::sort(Sequences.begin(), Sequences.end(), Sequence::orderByLowPC); 130 // Note: actually, instruction address ranges of sequences should not 131 // overlap (in shared objects and executables). If they do, the address 132 // lookup would still work, though, but result would be ambiguous. 133 // We don't report warning in this case. For example, 134 // sometimes .so compiled from multiple object files contains a few 135 // rudimentary sequences for address ranges [0x0, 0xsomething). 136 } 137} 138 139DWARFDebugLine::DumpingState::~DumpingState() {} 140 141void DWARFDebugLine::DumpingState::finalize() { 142 LineTable::dump(OS); 143} 144 145const DWARFDebugLine::LineTable * 146DWARFDebugLine::getLineTable(uint32_t offset) const { 147 LineTableConstIter pos = LineTableMap.find(offset); 148 if (pos != LineTableMap.end()) 149 return &pos->second; 150 return 0; 151} 152 153const DWARFDebugLine::LineTable * 154DWARFDebugLine::getOrParseLineTable(DataExtractor debug_line_data, 155 uint32_t offset) { 156 std::pair<LineTableIter, bool> pos = 157 LineTableMap.insert(LineTableMapTy::value_type(offset, LineTable())); 158 if (pos.second) { 159 // Parse and cache the line table for at this offset. 160 State state; 161 if (!parseStatementTable(debug_line_data, RelocMap, &offset, state)) 162 return 0; 163 pos.first->second = state; 164 } 165 return &pos.first->second; 166} 167 168bool 169DWARFDebugLine::parsePrologue(DataExtractor debug_line_data, 170 uint32_t *offset_ptr, Prologue *prologue) { 171 const uint32_t prologue_offset = *offset_ptr; 172 173 prologue->clear(); 174 prologue->TotalLength = debug_line_data.getU32(offset_ptr); 175 prologue->Version = debug_line_data.getU16(offset_ptr); 176 if (prologue->Version < 2) 177 return false; 178 179 prologue->PrologueLength = debug_line_data.getU32(offset_ptr); 180 const uint32_t end_prologue_offset = prologue->PrologueLength + *offset_ptr; 181 prologue->MinInstLength = debug_line_data.getU8(offset_ptr); 182 if (prologue->Version >= 4) 183 prologue->MaxOpsPerInst = debug_line_data.getU8(offset_ptr); 184 prologue->DefaultIsStmt = debug_line_data.getU8(offset_ptr); 185 prologue->LineBase = debug_line_data.getU8(offset_ptr); 186 prologue->LineRange = debug_line_data.getU8(offset_ptr); 187 prologue->OpcodeBase = debug_line_data.getU8(offset_ptr); 188 189 prologue->StandardOpcodeLengths.reserve(prologue->OpcodeBase-1); 190 for (uint32_t i = 1; i < prologue->OpcodeBase; ++i) { 191 uint8_t op_len = debug_line_data.getU8(offset_ptr); 192 prologue->StandardOpcodeLengths.push_back(op_len); 193 } 194 195 while (*offset_ptr < end_prologue_offset) { 196 const char *s = debug_line_data.getCStr(offset_ptr); 197 if (s && s[0]) 198 prologue->IncludeDirectories.push_back(s); 199 else 200 break; 201 } 202 203 while (*offset_ptr < end_prologue_offset) { 204 const char *name = debug_line_data.getCStr(offset_ptr); 205 if (name && name[0]) { 206 FileNameEntry fileEntry; 207 fileEntry.Name = name; 208 fileEntry.DirIdx = debug_line_data.getULEB128(offset_ptr); 209 fileEntry.ModTime = debug_line_data.getULEB128(offset_ptr); 210 fileEntry.Length = debug_line_data.getULEB128(offset_ptr); 211 prologue->FileNames.push_back(fileEntry); 212 } else { 213 break; 214 } 215 } 216 217 if (*offset_ptr != end_prologue_offset) { 218 fprintf(stderr, "warning: parsing line table prologue at 0x%8.8x should" 219 " have ended at 0x%8.8x but it ended at 0x%8.8x\n", 220 prologue_offset, end_prologue_offset, *offset_ptr); 221 return false; 222 } 223 return true; 224} 225 226bool DWARFDebugLine::parseStatementTable(DataExtractor debug_line_data, 227 const RelocAddrMap *RMap, 228 uint32_t *offset_ptr, State &state) { 229 const uint32_t debug_line_offset = *offset_ptr; 230 231 Prologue *prologue = &state.Prologue; 232 233 if (!parsePrologue(debug_line_data, offset_ptr, prologue)) { 234 // Restore our offset and return false to indicate failure! 235 *offset_ptr = debug_line_offset; 236 return false; 237 } 238 239 const uint32_t end_offset = debug_line_offset + prologue->TotalLength + 240 sizeof(prologue->TotalLength); 241 242 state.reset(); 243 244 while (*offset_ptr < end_offset) { 245 uint8_t opcode = debug_line_data.getU8(offset_ptr); 246 247 if (opcode == 0) { 248 // Extended Opcodes always start with a zero opcode followed by 249 // a uleb128 length so you can skip ones you don't know about 250 uint32_t ext_offset = *offset_ptr; 251 uint64_t len = debug_line_data.getULEB128(offset_ptr); 252 uint32_t arg_size = len - (*offset_ptr - ext_offset); 253 254 uint8_t sub_opcode = debug_line_data.getU8(offset_ptr); 255 switch (sub_opcode) { 256 case DW_LNE_end_sequence: 257 // Set the end_sequence register of the state machine to true and 258 // append a row to the matrix using the current values of the 259 // state-machine registers. Then reset the registers to the initial 260 // values specified above. Every statement program sequence must end 261 // with a DW_LNE_end_sequence instruction which creates a row whose 262 // address is that of the byte after the last target machine instruction 263 // of the sequence. 264 state.EndSequence = true; 265 state.appendRowToMatrix(*offset_ptr); 266 state.reset(); 267 break; 268 269 case DW_LNE_set_address: 270 // Takes a single relocatable address as an operand. The size of the 271 // operand is the size appropriate to hold an address on the target 272 // machine. Set the address register to the value given by the 273 // relocatable address. All of the other statement program opcodes 274 // that affect the address register add a delta to it. This instruction 275 // stores a relocatable value into it instead. 276 { 277 // If this address is in our relocation map, apply the relocation. 278 RelocAddrMap::const_iterator AI = RMap->find(*offset_ptr); 279 if (AI != RMap->end()) { 280 const std::pair<uint8_t, int64_t> &R = AI->second; 281 state.Address = debug_line_data.getAddress(offset_ptr) + R.second; 282 } else 283 state.Address = debug_line_data.getAddress(offset_ptr); 284 } 285 break; 286 287 case DW_LNE_define_file: 288 // Takes 4 arguments. The first is a null terminated string containing 289 // a source file name. The second is an unsigned LEB128 number 290 // representing the directory index of the directory in which the file 291 // was found. The third is an unsigned LEB128 number representing the 292 // time of last modification of the file. The fourth is an unsigned 293 // LEB128 number representing the length in bytes of the file. The time 294 // and length fields may contain LEB128(0) if the information is not 295 // available. 296 // 297 // The directory index represents an entry in the include_directories 298 // section of the statement program prologue. The index is LEB128(0) 299 // if the file was found in the current directory of the compilation, 300 // LEB128(1) if it was found in the first directory in the 301 // include_directories section, and so on. The directory index is 302 // ignored for file names that represent full path names. 303 // 304 // The files are numbered, starting at 1, in the order in which they 305 // appear; the names in the prologue come before names defined by 306 // the DW_LNE_define_file instruction. These numbers are used in the 307 // the file register of the state machine. 308 { 309 FileNameEntry fileEntry; 310 fileEntry.Name = debug_line_data.getCStr(offset_ptr); 311 fileEntry.DirIdx = debug_line_data.getULEB128(offset_ptr); 312 fileEntry.ModTime = debug_line_data.getULEB128(offset_ptr); 313 fileEntry.Length = debug_line_data.getULEB128(offset_ptr); 314 prologue->FileNames.push_back(fileEntry); 315 } 316 break; 317 318 case DW_LNE_set_discriminator: 319 state.Discriminator = debug_line_data.getULEB128(offset_ptr); 320 break; 321 322 default: 323 // Length doesn't include the zero opcode byte or the length itself, but 324 // it does include the sub_opcode, so we have to adjust for that below 325 (*offset_ptr) += arg_size; 326 break; 327 } 328 } else if (opcode < prologue->OpcodeBase) { 329 switch (opcode) { 330 // Standard Opcodes 331 case DW_LNS_copy: 332 // Takes no arguments. Append a row to the matrix using the 333 // current values of the state-machine registers. Then set 334 // the basic_block register to false. 335 state.appendRowToMatrix(*offset_ptr); 336 break; 337 338 case DW_LNS_advance_pc: 339 // Takes a single unsigned LEB128 operand, multiplies it by the 340 // min_inst_length field of the prologue, and adds the 341 // result to the address register of the state machine. 342 state.Address += debug_line_data.getULEB128(offset_ptr) * 343 prologue->MinInstLength; 344 break; 345 346 case DW_LNS_advance_line: 347 // Takes a single signed LEB128 operand and adds that value to 348 // the line register of the state machine. 349 state.Line += debug_line_data.getSLEB128(offset_ptr); 350 break; 351 352 case DW_LNS_set_file: 353 // Takes a single unsigned LEB128 operand and stores it in the file 354 // register of the state machine. 355 state.File = debug_line_data.getULEB128(offset_ptr); 356 break; 357 358 case DW_LNS_set_column: 359 // Takes a single unsigned LEB128 operand and stores it in the 360 // column register of the state machine. 361 state.Column = debug_line_data.getULEB128(offset_ptr); 362 break; 363 364 case DW_LNS_negate_stmt: 365 // Takes no arguments. Set the is_stmt register of the state 366 // machine to the logical negation of its current value. 367 state.IsStmt = !state.IsStmt; 368 break; 369 370 case DW_LNS_set_basic_block: 371 // Takes no arguments. Set the basic_block register of the 372 // state machine to true 373 state.BasicBlock = true; 374 break; 375 376 case DW_LNS_const_add_pc: 377 // Takes no arguments. Add to the address register of the state 378 // machine the address increment value corresponding to special 379 // opcode 255. The motivation for DW_LNS_const_add_pc is this: 380 // when the statement program needs to advance the address by a 381 // small amount, it can use a single special opcode, which occupies 382 // a single byte. When it needs to advance the address by up to 383 // twice the range of the last special opcode, it can use 384 // DW_LNS_const_add_pc followed by a special opcode, for a total 385 // of two bytes. Only if it needs to advance the address by more 386 // than twice that range will it need to use both DW_LNS_advance_pc 387 // and a special opcode, requiring three or more bytes. 388 { 389 uint8_t adjust_opcode = 255 - prologue->OpcodeBase; 390 uint64_t addr_offset = (adjust_opcode / prologue->LineRange) * 391 prologue->MinInstLength; 392 state.Address += addr_offset; 393 } 394 break; 395 396 case DW_LNS_fixed_advance_pc: 397 // Takes a single uhalf operand. Add to the address register of 398 // the state machine the value of the (unencoded) operand. This 399 // is the only extended opcode that takes an argument that is not 400 // a variable length number. The motivation for DW_LNS_fixed_advance_pc 401 // is this: existing assemblers cannot emit DW_LNS_advance_pc or 402 // special opcodes because they cannot encode LEB128 numbers or 403 // judge when the computation of a special opcode overflows and 404 // requires the use of DW_LNS_advance_pc. Such assemblers, however, 405 // can use DW_LNS_fixed_advance_pc instead, sacrificing compression. 406 state.Address += debug_line_data.getU16(offset_ptr); 407 break; 408 409 case DW_LNS_set_prologue_end: 410 // Takes no arguments. Set the prologue_end register of the 411 // state machine to true 412 state.PrologueEnd = true; 413 break; 414 415 case DW_LNS_set_epilogue_begin: 416 // Takes no arguments. Set the basic_block register of the 417 // state machine to true 418 state.EpilogueBegin = true; 419 break; 420 421 case DW_LNS_set_isa: 422 // Takes a single unsigned LEB128 operand and stores it in the 423 // column register of the state machine. 424 state.Isa = debug_line_data.getULEB128(offset_ptr); 425 break; 426 427 default: 428 // Handle any unknown standard opcodes here. We know the lengths 429 // of such opcodes because they are specified in the prologue 430 // as a multiple of LEB128 operands for each opcode. 431 { 432 assert(opcode - 1U < prologue->StandardOpcodeLengths.size()); 433 uint8_t opcode_length = prologue->StandardOpcodeLengths[opcode - 1]; 434 for (uint8_t i=0; i<opcode_length; ++i) 435 debug_line_data.getULEB128(offset_ptr); 436 } 437 break; 438 } 439 } else { 440 // Special Opcodes 441 442 // A special opcode value is chosen based on the amount that needs 443 // to be added to the line and address registers. The maximum line 444 // increment for a special opcode is the value of the line_base 445 // field in the header, plus the value of the line_range field, 446 // minus 1 (line base + line range - 1). If the desired line 447 // increment is greater than the maximum line increment, a standard 448 // opcode must be used instead of a special opcode. The "address 449 // advance" is calculated by dividing the desired address increment 450 // by the minimum_instruction_length field from the header. The 451 // special opcode is then calculated using the following formula: 452 // 453 // opcode = (desired line increment - line_base) + 454 // (line_range * address advance) + opcode_base 455 // 456 // If the resulting opcode is greater than 255, a standard opcode 457 // must be used instead. 458 // 459 // To decode a special opcode, subtract the opcode_base from the 460 // opcode itself to give the adjusted opcode. The amount to 461 // increment the address register is the result of the adjusted 462 // opcode divided by the line_range multiplied by the 463 // minimum_instruction_length field from the header. That is: 464 // 465 // address increment = (adjusted opcode / line_range) * 466 // minimum_instruction_length 467 // 468 // The amount to increment the line register is the line_base plus 469 // the result of the adjusted opcode modulo the line_range. That is: 470 // 471 // line increment = line_base + (adjusted opcode % line_range) 472 473 uint8_t adjust_opcode = opcode - prologue->OpcodeBase; 474 uint64_t addr_offset = (adjust_opcode / prologue->LineRange) * 475 prologue->MinInstLength; 476 int32_t line_offset = prologue->LineBase + 477 (adjust_opcode % prologue->LineRange); 478 state.Line += line_offset; 479 state.Address += addr_offset; 480 state.appendRowToMatrix(*offset_ptr); 481 } 482 } 483 484 state.finalize(); 485 486 return end_offset; 487} 488 489uint32_t 490DWARFDebugLine::LineTable::lookupAddress(uint64_t address) const { 491 uint32_t unknown_index = UINT32_MAX; 492 if (Sequences.empty()) 493 return unknown_index; 494 // First, find an instruction sequence containing the given address. 495 DWARFDebugLine::Sequence sequence; 496 sequence.LowPC = address; 497 SequenceIter first_seq = Sequences.begin(); 498 SequenceIter last_seq = Sequences.end(); 499 SequenceIter seq_pos = std::lower_bound(first_seq, last_seq, sequence, 500 DWARFDebugLine::Sequence::orderByLowPC); 501 DWARFDebugLine::Sequence found_seq; 502 if (seq_pos == last_seq) { 503 found_seq = Sequences.back(); 504 } else if (seq_pos->LowPC == address) { 505 found_seq = *seq_pos; 506 } else { 507 if (seq_pos == first_seq) 508 return unknown_index; 509 found_seq = *(seq_pos - 1); 510 } 511 if (!found_seq.containsPC(address)) 512 return unknown_index; 513 // Search for instruction address in the rows describing the sequence. 514 // Rows are stored in a vector, so we may use arithmetical operations with 515 // iterators. 516 DWARFDebugLine::Row row; 517 row.Address = address; 518 RowIter first_row = Rows.begin() + found_seq.FirstRowIndex; 519 RowIter last_row = Rows.begin() + found_seq.LastRowIndex; 520 RowIter row_pos = std::lower_bound(first_row, last_row, row, 521 DWARFDebugLine::Row::orderByAddress); 522 if (row_pos == last_row) { 523 return found_seq.LastRowIndex - 1; 524 } 525 uint32_t index = found_seq.FirstRowIndex + (row_pos - first_row); 526 if (row_pos->Address > address) { 527 if (row_pos == first_row) 528 return unknown_index; 529 else 530 index--; 531 } 532 return index; 533} 534 535bool 536DWARFDebugLine::LineTable::lookupAddressRange(uint64_t address, 537 uint64_t size, 538 std::vector<uint32_t>& result) const { 539 if (Sequences.empty()) 540 return false; 541 uint64_t end_addr = address + size; 542 // First, find an instruction sequence containing the given address. 543 DWARFDebugLine::Sequence sequence; 544 sequence.LowPC = address; 545 SequenceIter first_seq = Sequences.begin(); 546 SequenceIter last_seq = Sequences.end(); 547 SequenceIter seq_pos = std::lower_bound(first_seq, last_seq, sequence, 548 DWARFDebugLine::Sequence::orderByLowPC); 549 if (seq_pos == last_seq || seq_pos->LowPC != address) { 550 if (seq_pos == first_seq) 551 return false; 552 seq_pos--; 553 } 554 if (!seq_pos->containsPC(address)) 555 return false; 556 557 SequenceIter start_pos = seq_pos; 558 559 // Add the rows from the first sequence to the vector, starting with the 560 // index we just calculated 561 562 while (seq_pos != last_seq && seq_pos->LowPC < end_addr) { 563 DWARFDebugLine::Sequence cur_seq = *seq_pos; 564 uint32_t first_row_index; 565 uint32_t last_row_index; 566 if (seq_pos == start_pos) { 567 // For the first sequence, we need to find which row in the sequence is the 568 // first in our range. Rows are stored in a vector, so we may use 569 // arithmetical operations with iterators. 570 DWARFDebugLine::Row row; 571 row.Address = address; 572 RowIter first_row = Rows.begin() + cur_seq.FirstRowIndex; 573 RowIter last_row = Rows.begin() + cur_seq.LastRowIndex; 574 RowIter row_pos = std::upper_bound(first_row, last_row, row, 575 DWARFDebugLine::Row::orderByAddress); 576 // The 'row_pos' iterator references the first row that is greater than 577 // our start address. Unless that's the first row, we want to start at 578 // the row before that. 579 first_row_index = cur_seq.FirstRowIndex + (row_pos - first_row); 580 if (row_pos != first_row) 581 --first_row_index; 582 } else 583 first_row_index = cur_seq.FirstRowIndex; 584 585 // For the last sequence in our range, we need to figure out the last row in 586 // range. For all other sequences we can go to the end of the sequence. 587 if (cur_seq.HighPC > end_addr) { 588 DWARFDebugLine::Row row; 589 row.Address = end_addr; 590 RowIter first_row = Rows.begin() + cur_seq.FirstRowIndex; 591 RowIter last_row = Rows.begin() + cur_seq.LastRowIndex; 592 RowIter row_pos = std::upper_bound(first_row, last_row, row, 593 DWARFDebugLine::Row::orderByAddress); 594 // The 'row_pos' iterator references the first row that is greater than 595 // our end address. The row before that is the last row we want. 596 last_row_index = cur_seq.FirstRowIndex + (row_pos - first_row) - 1; 597 } else 598 // Contrary to what you might expect, DWARFDebugLine::SequenceLastRowIndex 599 // isn't a valid index within the current sequence. It's that plus one. 600 last_row_index = cur_seq.LastRowIndex - 1; 601 602 for (uint32_t i = first_row_index; i <= last_row_index; ++i) { 603 result.push_back(i); 604 } 605 606 ++seq_pos; 607 } 608 609 return true; 610} 611 612bool 613DWARFDebugLine::LineTable::getFileNameByIndex(uint64_t FileIndex, 614 bool NeedsAbsoluteFilePath, 615 std::string &Result) const { 616 if (FileIndex == 0 || FileIndex > Prologue.FileNames.size()) 617 return false; 618 const FileNameEntry &Entry = Prologue.FileNames[FileIndex - 1]; 619 const char *FileName = Entry.Name; 620 if (!NeedsAbsoluteFilePath || 621 sys::path::is_absolute(FileName)) { 622 Result = FileName; 623 return true; 624 } 625 SmallString<16> FilePath; 626 uint64_t IncludeDirIndex = Entry.DirIdx; 627 // Be defensive about the contents of Entry. 628 if (IncludeDirIndex > 0 && 629 IncludeDirIndex <= Prologue.IncludeDirectories.size()) { 630 const char *IncludeDir = Prologue.IncludeDirectories[IncludeDirIndex - 1]; 631 sys::path::append(FilePath, IncludeDir); 632 } 633 sys::path::append(FilePath, FileName); 634 Result = FilePath.str(); 635 return true; 636} 637