1 //===- InterpolatingCompilationDatabase.cpp ---------------------*- 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 // InterpolatingCompilationDatabase wraps another CompilationDatabase and 10 // attempts to heuristically determine appropriate compile commands for files 11 // that are not included, such as headers or newly created files. 12 // 13 // Motivating cases include: 14 // Header files that live next to their implementation files. These typically 15 // share a base filename. (libclang/CXString.h, libclang/CXString.cpp). 16 // Some projects separate headers from includes. Filenames still typically 17 // match, maybe other path segments too. (include/llvm/IR/Use.h, lib/IR/Use.cc). 18 // Matches are sometimes only approximate (Sema.h, SemaDecl.cpp). This goes 19 // for directories too (Support/Unix/Process.inc, lib/Support/Process.cpp). 20 // Even if we can't find a "right" compile command, even a random one from 21 // the project will tend to get important flags like -I and -x right. 22 // 23 // We "borrow" the compile command for the closest available file: 24 // - points are awarded if the filename matches (ignoring extension) 25 // - points are awarded if the directory structure matches 26 // - ties are broken by length of path prefix match 27 // 28 // The compile command is adjusted, replacing the filename and removing output 29 // file arguments. The -x and -std flags may be affected too. 30 // 31 // Source language is a tricky issue: is it OK to use a .c file's command 32 // for building a .cc file? What language is a .h file in? 33 // - We only consider compile commands for c-family languages as candidates. 34 // - For files whose language is implied by the filename (e.g. .m, .hpp) 35 // we prefer candidates from the same language. 36 // If we must cross languages, we drop any -x and -std flags. 37 // - For .h files, candidates from any c-family language are acceptable. 38 // We use the candidate's language, inserting e.g. -x c++-header. 39 // 40 // This class is only useful when wrapping databases that can enumerate all 41 // their compile commands. If getAllFilenames() is empty, no inference occurs. 42 // 43 //===----------------------------------------------------------------------===// 44 45 #include "clang/Basic/LangStandard.h" 46 #include "clang/Driver/Driver.h" 47 #include "clang/Driver/Options.h" 48 #include "clang/Driver/Types.h" 49 #include "clang/Tooling/CompilationDatabase.h" 50 #include "llvm/ADT/ArrayRef.h" 51 #include "llvm/ADT/DenseMap.h" 52 #include "llvm/ADT/StringExtras.h" 53 #include "llvm/Option/ArgList.h" 54 #include "llvm/Option/OptTable.h" 55 #include "llvm/Support/Debug.h" 56 #include "llvm/Support/Path.h" 57 #include "llvm/Support/StringSaver.h" 58 #include "llvm/Support/raw_ostream.h" 59 #include <memory> 60 #include <optional> 61 62 namespace clang { 63 namespace tooling { 64 namespace { 65 using namespace llvm; 66 namespace types = clang::driver::types; 67 namespace path = llvm::sys::path; 68 69 // The length of the prefix these two strings have in common. 70 size_t matchingPrefix(StringRef L, StringRef R) { 71 size_t Limit = std::min(L.size(), R.size()); 72 for (size_t I = 0; I < Limit; ++I) 73 if (L[I] != R[I]) 74 return I; 75 return Limit; 76 } 77 78 // A comparator for searching SubstringWithIndexes with std::equal_range etc. 79 // Optionaly prefix semantics: compares equal if the key is a prefix. 80 template <bool Prefix> struct Less { 81 bool operator()(StringRef Key, std::pair<StringRef, size_t> Value) const { 82 StringRef V = Prefix ? Value.first.substr(0, Key.size()) : Value.first; 83 return Key < V; 84 } 85 bool operator()(std::pair<StringRef, size_t> Value, StringRef Key) const { 86 StringRef V = Prefix ? Value.first.substr(0, Key.size()) : Value.first; 87 return V < Key; 88 } 89 }; 90 91 // Infer type from filename. If we might have gotten it wrong, set *Certain. 92 // *.h will be inferred as a C header, but not certain. 93 types::ID guessType(StringRef Filename, bool *Certain = nullptr) { 94 // path::extension is ".cpp", lookupTypeForExtension wants "cpp". 95 auto Lang = 96 types::lookupTypeForExtension(path::extension(Filename).substr(1)); 97 if (Certain) 98 *Certain = Lang != types::TY_CHeader && Lang != types::TY_INVALID; 99 return Lang; 100 } 101 102 // Return Lang as one of the canonical supported types. 103 // e.g. c-header --> c; fortran --> TY_INVALID 104 static types::ID foldType(types::ID Lang) { 105 switch (Lang) { 106 case types::TY_C: 107 case types::TY_CHeader: 108 return types::TY_C; 109 case types::TY_ObjC: 110 case types::TY_ObjCHeader: 111 return types::TY_ObjC; 112 case types::TY_CXX: 113 case types::TY_CXXHeader: 114 return types::TY_CXX; 115 case types::TY_ObjCXX: 116 case types::TY_ObjCXXHeader: 117 return types::TY_ObjCXX; 118 case types::TY_CUDA: 119 case types::TY_CUDA_DEVICE: 120 return types::TY_CUDA; 121 default: 122 return types::TY_INVALID; 123 } 124 } 125 126 // A CompileCommand that can be applied to another file. 127 struct TransferableCommand { 128 // Flags that should not apply to all files are stripped from CommandLine. 129 CompileCommand Cmd; 130 // Language detected from -x or the filename. Never TY_INVALID. 131 std::optional<types::ID> Type; 132 // Standard specified by -std. 133 LangStandard::Kind Std = LangStandard::lang_unspecified; 134 // Whether the command line is for the cl-compatible driver. 135 bool ClangCLMode; 136 137 TransferableCommand(CompileCommand C) 138 : Cmd(std::move(C)), Type(guessType(Cmd.Filename)) { 139 std::vector<std::string> OldArgs = std::move(Cmd.CommandLine); 140 Cmd.CommandLine.clear(); 141 142 // Wrap the old arguments in an InputArgList. 143 llvm::opt::InputArgList ArgList; 144 { 145 SmallVector<const char *, 16> TmpArgv; 146 for (const std::string &S : OldArgs) 147 TmpArgv.push_back(S.c_str()); 148 ClangCLMode = !TmpArgv.empty() && 149 driver::IsClangCL(driver::getDriverMode( 150 TmpArgv.front(), llvm::ArrayRef(TmpArgv).slice(1))); 151 ArgList = {TmpArgv.begin(), TmpArgv.end()}; 152 } 153 154 // Parse the old args in order to strip out and record unwanted flags. 155 // We parse each argument individually so that we can retain the exact 156 // spelling of each argument; re-rendering is lossy for aliased flags. 157 // E.g. in CL mode, /W4 maps to -Wall. 158 auto &OptTable = clang::driver::getDriverOptTable(); 159 if (!OldArgs.empty()) 160 Cmd.CommandLine.emplace_back(OldArgs.front()); 161 for (unsigned Pos = 1; Pos < OldArgs.size();) { 162 using namespace driver::options; 163 164 const unsigned OldPos = Pos; 165 std::unique_ptr<llvm::opt::Arg> Arg(OptTable.ParseOneArg( 166 ArgList, Pos, 167 llvm::opt::Visibility(ClangCLMode ? CLOption : ClangOption))); 168 169 if (!Arg) 170 continue; 171 172 const llvm::opt::Option &Opt = Arg->getOption(); 173 174 // Strip input and output files. 175 if (Opt.matches(OPT_INPUT) || Opt.matches(OPT_o) || 176 (ClangCLMode && (Opt.matches(OPT__SLASH_Fa) || 177 Opt.matches(OPT__SLASH_Fe) || 178 Opt.matches(OPT__SLASH_Fi) || 179 Opt.matches(OPT__SLASH_Fo)))) 180 continue; 181 182 // ...including when the inputs are passed after --. 183 if (Opt.matches(OPT__DASH_DASH)) 184 break; 185 186 // Strip -x, but record the overridden language. 187 if (const auto GivenType = tryParseTypeArg(*Arg)) { 188 Type = *GivenType; 189 continue; 190 } 191 192 // Strip -std, but record the value. 193 if (const auto GivenStd = tryParseStdArg(*Arg)) { 194 if (*GivenStd != LangStandard::lang_unspecified) 195 Std = *GivenStd; 196 continue; 197 } 198 199 Cmd.CommandLine.insert(Cmd.CommandLine.end(), 200 OldArgs.data() + OldPos, OldArgs.data() + Pos); 201 } 202 203 // Make use of -std iff -x was missing. 204 if (Type == types::TY_INVALID && Std != LangStandard::lang_unspecified) 205 Type = toType(LangStandard::getLangStandardForKind(Std).getLanguage()); 206 Type = foldType(*Type); 207 // The contract is to store None instead of TY_INVALID. 208 if (Type == types::TY_INVALID) 209 Type = std::nullopt; 210 } 211 212 // Produce a CompileCommand for \p filename, based on this one. 213 // (This consumes the TransferableCommand just to avoid copying Cmd). 214 CompileCommand transferTo(StringRef Filename) && { 215 CompileCommand Result = std::move(Cmd); 216 Result.Heuristic = "inferred from " + Result.Filename; 217 Result.Filename = std::string(Filename); 218 bool TypeCertain; 219 auto TargetType = guessType(Filename, &TypeCertain); 220 // If the filename doesn't determine the language (.h), transfer with -x. 221 if ((!TargetType || !TypeCertain) && Type) { 222 // Use *Type, or its header variant if the file is a header. 223 // Treat no/invalid extension as header (e.g. C++ standard library). 224 TargetType = 225 (!TargetType || types::onlyPrecompileType(TargetType)) // header? 226 ? types::lookupHeaderTypeForSourceType(*Type) 227 : *Type; 228 if (ClangCLMode) { 229 const StringRef Flag = toCLFlag(TargetType); 230 if (!Flag.empty()) 231 Result.CommandLine.push_back(std::string(Flag)); 232 } else { 233 Result.CommandLine.push_back("-x"); 234 Result.CommandLine.push_back(types::getTypeName(TargetType)); 235 } 236 } 237 // --std flag may only be transferred if the language is the same. 238 // We may consider "translating" these, e.g. c++11 -> c11. 239 if (Std != LangStandard::lang_unspecified && foldType(TargetType) == Type) { 240 Result.CommandLine.emplace_back(( 241 llvm::Twine(ClangCLMode ? "/std:" : "-std=") + 242 LangStandard::getLangStandardForKind(Std).getName()).str()); 243 } 244 Result.CommandLine.push_back("--"); 245 Result.CommandLine.push_back(std::string(Filename)); 246 return Result; 247 } 248 249 private: 250 // Map the language from the --std flag to that of the -x flag. 251 static types::ID toType(Language Lang) { 252 switch (Lang) { 253 case Language::C: 254 return types::TY_C; 255 case Language::CXX: 256 return types::TY_CXX; 257 case Language::ObjC: 258 return types::TY_ObjC; 259 case Language::ObjCXX: 260 return types::TY_ObjCXX; 261 default: 262 return types::TY_INVALID; 263 } 264 } 265 266 // Convert a file type to the matching CL-style type flag. 267 static StringRef toCLFlag(types::ID Type) { 268 switch (Type) { 269 case types::TY_C: 270 case types::TY_CHeader: 271 return "/TC"; 272 case types::TY_CXX: 273 case types::TY_CXXHeader: 274 return "/TP"; 275 default: 276 return StringRef(); 277 } 278 } 279 280 // Try to interpret the argument as a type specifier, e.g. '-x'. 281 std::optional<types::ID> tryParseTypeArg(const llvm::opt::Arg &Arg) { 282 const llvm::opt::Option &Opt = Arg.getOption(); 283 using namespace driver::options; 284 if (ClangCLMode) { 285 if (Opt.matches(OPT__SLASH_TC) || Opt.matches(OPT__SLASH_Tc)) 286 return types::TY_C; 287 if (Opt.matches(OPT__SLASH_TP) || Opt.matches(OPT__SLASH_Tp)) 288 return types::TY_CXX; 289 } else { 290 if (Opt.matches(driver::options::OPT_x)) 291 return types::lookupTypeForTypeSpecifier(Arg.getValue()); 292 } 293 return std::nullopt; 294 } 295 296 // Try to interpret the argument as '-std='. 297 std::optional<LangStandard::Kind> tryParseStdArg(const llvm::opt::Arg &Arg) { 298 using namespace driver::options; 299 if (Arg.getOption().matches(ClangCLMode ? OPT__SLASH_std : OPT_std_EQ)) 300 return LangStandard::getLangKind(Arg.getValue()); 301 return std::nullopt; 302 } 303 }; 304 305 // Given a filename, FileIndex picks the best matching file from the underlying 306 // DB. This is the proxy file whose CompileCommand will be reused. The 307 // heuristics incorporate file name, extension, and directory structure. 308 // Strategy: 309 // - Build indexes of each of the substrings we want to look up by. 310 // These indexes are just sorted lists of the substrings. 311 // - Each criterion corresponds to a range lookup into the index, so we only 312 // need O(log N) string comparisons to determine scores. 313 // 314 // Apart from path proximity signals, also takes file extensions into account 315 // when scoring the candidates. 316 class FileIndex { 317 public: 318 FileIndex(std::vector<std::string> Files) 319 : OriginalPaths(std::move(Files)), Strings(Arena) { 320 // Sort commands by filename for determinism (index is a tiebreaker later). 321 llvm::sort(OriginalPaths); 322 Paths.reserve(OriginalPaths.size()); 323 Types.reserve(OriginalPaths.size()); 324 Stems.reserve(OriginalPaths.size()); 325 for (size_t I = 0; I < OriginalPaths.size(); ++I) { 326 StringRef Path = Strings.save(StringRef(OriginalPaths[I]).lower()); 327 328 Paths.emplace_back(Path, I); 329 Types.push_back(foldType(guessType(OriginalPaths[I]))); 330 Stems.emplace_back(sys::path::stem(Path), I); 331 auto Dir = ++sys::path::rbegin(Path), DirEnd = sys::path::rend(Path); 332 for (int J = 0; J < DirectorySegmentsIndexed && Dir != DirEnd; ++J, ++Dir) 333 if (Dir->size() > ShortDirectorySegment) // not trivial ones 334 Components.emplace_back(*Dir, I); 335 } 336 llvm::sort(Paths); 337 llvm::sort(Stems); 338 llvm::sort(Components); 339 } 340 341 bool empty() const { return Paths.empty(); } 342 343 // Returns the path for the file that best fits OriginalFilename. 344 // Candidates with extensions matching PreferLanguage will be chosen over 345 // others (unless it's TY_INVALID, or all candidates are bad). 346 StringRef chooseProxy(StringRef OriginalFilename, 347 types::ID PreferLanguage) const { 348 assert(!empty() && "need at least one candidate!"); 349 std::string Filename = OriginalFilename.lower(); 350 auto Candidates = scoreCandidates(Filename); 351 std::pair<size_t, int> Best = 352 pickWinner(Candidates, Filename, PreferLanguage); 353 354 DEBUG_WITH_TYPE( 355 "interpolate", 356 llvm::dbgs() << "interpolate: chose " << OriginalPaths[Best.first] 357 << " as proxy for " << OriginalFilename << " preferring " 358 << (PreferLanguage == types::TY_INVALID 359 ? "none" 360 : types::getTypeName(PreferLanguage)) 361 << " score=" << Best.second << "\n"); 362 return OriginalPaths[Best.first]; 363 } 364 365 private: 366 using SubstringAndIndex = std::pair<StringRef, size_t>; 367 // Directory matching parameters: we look at the last two segments of the 368 // parent directory (usually the semantically significant ones in practice). 369 // We search only the last four of each candidate (for efficiency). 370 constexpr static int DirectorySegmentsIndexed = 4; 371 constexpr static int DirectorySegmentsQueried = 2; 372 constexpr static int ShortDirectorySegment = 1; // Only look at longer names. 373 374 // Award points to candidate entries that should be considered for the file. 375 // Returned keys are indexes into paths, and the values are (nonzero) scores. 376 DenseMap<size_t, int> scoreCandidates(StringRef Filename) const { 377 // Decompose Filename into the parts we care about. 378 // /some/path/complicated/project/Interesting.h 379 // [-prefix--][---dir---] [-dir-] [--stem---] 380 StringRef Stem = sys::path::stem(Filename); 381 llvm::SmallVector<StringRef, DirectorySegmentsQueried> Dirs; 382 llvm::StringRef Prefix; 383 auto Dir = ++sys::path::rbegin(Filename), 384 DirEnd = sys::path::rend(Filename); 385 for (int I = 0; I < DirectorySegmentsQueried && Dir != DirEnd; ++I, ++Dir) { 386 if (Dir->size() > ShortDirectorySegment) 387 Dirs.push_back(*Dir); 388 Prefix = Filename.substr(0, Dir - DirEnd); 389 } 390 391 // Now award points based on lookups into our various indexes. 392 DenseMap<size_t, int> Candidates; // Index -> score. 393 auto Award = [&](int Points, ArrayRef<SubstringAndIndex> Range) { 394 for (const auto &Entry : Range) 395 Candidates[Entry.second] += Points; 396 }; 397 // Award one point if the file's basename is a prefix of the candidate, 398 // and another if it's an exact match (so exact matches get two points). 399 Award(1, indexLookup</*Prefix=*/true>(Stem, Stems)); 400 Award(1, indexLookup</*Prefix=*/false>(Stem, Stems)); 401 // For each of the last few directories in the Filename, award a point 402 // if it's present in the candidate. 403 for (StringRef Dir : Dirs) 404 Award(1, indexLookup</*Prefix=*/false>(Dir, Components)); 405 // Award one more point if the whole rest of the path matches. 406 if (sys::path::root_directory(Prefix) != Prefix) 407 Award(1, indexLookup</*Prefix=*/true>(Prefix, Paths)); 408 return Candidates; 409 } 410 411 // Pick a single winner from the set of scored candidates. 412 // Returns (index, score). 413 std::pair<size_t, int> pickWinner(const DenseMap<size_t, int> &Candidates, 414 StringRef Filename, 415 types::ID PreferredLanguage) const { 416 struct ScoredCandidate { 417 size_t Index; 418 bool Preferred; 419 int Points; 420 size_t PrefixLength; 421 }; 422 // Choose the best candidate by (preferred, points, prefix length, alpha). 423 ScoredCandidate Best = {size_t(-1), false, 0, 0}; 424 for (const auto &Candidate : Candidates) { 425 ScoredCandidate S; 426 S.Index = Candidate.first; 427 S.Preferred = PreferredLanguage == types::TY_INVALID || 428 PreferredLanguage == Types[S.Index]; 429 S.Points = Candidate.second; 430 if (!S.Preferred && Best.Preferred) 431 continue; 432 if (S.Preferred == Best.Preferred) { 433 if (S.Points < Best.Points) 434 continue; 435 if (S.Points == Best.Points) { 436 S.PrefixLength = matchingPrefix(Filename, Paths[S.Index].first); 437 if (S.PrefixLength < Best.PrefixLength) 438 continue; 439 // hidden heuristics should at least be deterministic! 440 if (S.PrefixLength == Best.PrefixLength) 441 if (S.Index > Best.Index) 442 continue; 443 } 444 } 445 // PrefixLength was only set above if actually needed for a tiebreak. 446 // But it definitely needs to be set to break ties in the future. 447 S.PrefixLength = matchingPrefix(Filename, Paths[S.Index].first); 448 Best = S; 449 } 450 // Edge case: no candidate got any points. 451 // We ignore PreferredLanguage at this point (not ideal). 452 if (Best.Index == size_t(-1)) 453 return {longestMatch(Filename, Paths).second, 0}; 454 return {Best.Index, Best.Points}; 455 } 456 457 // Returns the range within a sorted index that compares equal to Key. 458 // If Prefix is true, it's instead the range starting with Key. 459 template <bool Prefix> 460 ArrayRef<SubstringAndIndex> 461 indexLookup(StringRef Key, ArrayRef<SubstringAndIndex> Idx) const { 462 // Use pointers as iteratiors to ease conversion of result to ArrayRef. 463 auto Range = std::equal_range(Idx.data(), Idx.data() + Idx.size(), Key, 464 Less<Prefix>()); 465 return {Range.first, Range.second}; 466 } 467 468 // Performs a point lookup into a nonempty index, returning a longest match. 469 SubstringAndIndex longestMatch(StringRef Key, 470 ArrayRef<SubstringAndIndex> Idx) const { 471 assert(!Idx.empty()); 472 // Longest substring match will be adjacent to a direct lookup. 473 auto It = llvm::lower_bound(Idx, SubstringAndIndex{Key, 0}); 474 if (It == Idx.begin()) 475 return *It; 476 if (It == Idx.end()) 477 return *--It; 478 // Have to choose between It and It-1 479 size_t Prefix = matchingPrefix(Key, It->first); 480 size_t PrevPrefix = matchingPrefix(Key, (It - 1)->first); 481 return Prefix > PrevPrefix ? *It : *--It; 482 } 483 484 // Original paths, everything else is in lowercase. 485 std::vector<std::string> OriginalPaths; 486 BumpPtrAllocator Arena; 487 StringSaver Strings; 488 // Indexes of candidates by certain substrings. 489 // String is lowercase and sorted, index points into OriginalPaths. 490 std::vector<SubstringAndIndex> Paths; // Full path. 491 // Lang types obtained by guessing on the corresponding path. I-th element is 492 // a type for the I-th path. 493 std::vector<types::ID> Types; 494 std::vector<SubstringAndIndex> Stems; // Basename, without extension. 495 std::vector<SubstringAndIndex> Components; // Last path components. 496 }; 497 498 // The actual CompilationDatabase wrapper delegates to its inner database. 499 // If no match, looks up a proxy file in FileIndex and transfers its 500 // command to the requested file. 501 class InterpolatingCompilationDatabase : public CompilationDatabase { 502 public: 503 InterpolatingCompilationDatabase(std::unique_ptr<CompilationDatabase> Inner) 504 : Inner(std::move(Inner)), Index(this->Inner->getAllFiles()) {} 505 506 std::vector<CompileCommand> 507 getCompileCommands(StringRef Filename) const override { 508 auto Known = Inner->getCompileCommands(Filename); 509 if (Index.empty() || !Known.empty()) 510 return Known; 511 bool TypeCertain; 512 auto Lang = guessType(Filename, &TypeCertain); 513 if (!TypeCertain) 514 Lang = types::TY_INVALID; 515 auto ProxyCommands = 516 Inner->getCompileCommands(Index.chooseProxy(Filename, foldType(Lang))); 517 if (ProxyCommands.empty()) 518 return {}; 519 return {transferCompileCommand(std::move(ProxyCommands.front()), Filename)}; 520 } 521 522 std::vector<std::string> getAllFiles() const override { 523 return Inner->getAllFiles(); 524 } 525 526 std::vector<CompileCommand> getAllCompileCommands() const override { 527 return Inner->getAllCompileCommands(); 528 } 529 530 private: 531 std::unique_ptr<CompilationDatabase> Inner; 532 FileIndex Index; 533 }; 534 535 } // namespace 536 537 std::unique_ptr<CompilationDatabase> 538 inferMissingCompileCommands(std::unique_ptr<CompilationDatabase> Inner) { 539 return std::make_unique<InterpolatingCompilationDatabase>(std::move(Inner)); 540 } 541 542 tooling::CompileCommand transferCompileCommand(CompileCommand Cmd, 543 StringRef Filename) { 544 return TransferableCommand(std::move(Cmd)).transferTo(Filename); 545 } 546 547 } // namespace tooling 548 } // namespace clang 549