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 /* Include */ ClangCLMode ? CoreOption | CLOption | CLDXCOption : 0, 168 /* Exclude */ ClangCLMode ? 0 : CLOption | CLDXCOption)); 169 170 if (!Arg) 171 continue; 172 173 const llvm::opt::Option &Opt = Arg->getOption(); 174 175 // Strip input and output files. 176 if (Opt.matches(OPT_INPUT) || Opt.matches(OPT_o) || 177 (ClangCLMode && (Opt.matches(OPT__SLASH_Fa) || 178 Opt.matches(OPT__SLASH_Fe) || 179 Opt.matches(OPT__SLASH_Fi) || 180 Opt.matches(OPT__SLASH_Fo)))) 181 continue; 182 183 // ...including when the inputs are passed after --. 184 if (Opt.matches(OPT__DASH_DASH)) 185 break; 186 187 // Strip -x, but record the overridden language. 188 if (const auto GivenType = tryParseTypeArg(*Arg)) { 189 Type = *GivenType; 190 continue; 191 } 192 193 // Strip -std, but record the value. 194 if (const auto GivenStd = tryParseStdArg(*Arg)) { 195 if (*GivenStd != LangStandard::lang_unspecified) 196 Std = *GivenStd; 197 continue; 198 } 199 200 Cmd.CommandLine.insert(Cmd.CommandLine.end(), 201 OldArgs.data() + OldPos, OldArgs.data() + Pos); 202 } 203 204 // Make use of -std iff -x was missing. 205 if (Type == types::TY_INVALID && Std != LangStandard::lang_unspecified) 206 Type = toType(LangStandard::getLangStandardForKind(Std).getLanguage()); 207 Type = foldType(*Type); 208 // The contract is to store None instead of TY_INVALID. 209 if (Type == types::TY_INVALID) 210 Type = std::nullopt; 211 } 212 213 // Produce a CompileCommand for \p filename, based on this one. 214 // (This consumes the TransferableCommand just to avoid copying Cmd). 215 CompileCommand transferTo(StringRef Filename) && { 216 CompileCommand Result = std::move(Cmd); 217 Result.Heuristic = "inferred from " + Result.Filename; 218 Result.Filename = std::string(Filename); 219 bool TypeCertain; 220 auto TargetType = guessType(Filename, &TypeCertain); 221 // If the filename doesn't determine the language (.h), transfer with -x. 222 if ((!TargetType || !TypeCertain) && Type) { 223 // Use *Type, or its header variant if the file is a header. 224 // Treat no/invalid extension as header (e.g. C++ standard library). 225 TargetType = 226 (!TargetType || types::onlyPrecompileType(TargetType)) // header? 227 ? types::lookupHeaderTypeForSourceType(*Type) 228 : *Type; 229 if (ClangCLMode) { 230 const StringRef Flag = toCLFlag(TargetType); 231 if (!Flag.empty()) 232 Result.CommandLine.push_back(std::string(Flag)); 233 } else { 234 Result.CommandLine.push_back("-x"); 235 Result.CommandLine.push_back(types::getTypeName(TargetType)); 236 } 237 } 238 // --std flag may only be transferred if the language is the same. 239 // We may consider "translating" these, e.g. c++11 -> c11. 240 if (Std != LangStandard::lang_unspecified && foldType(TargetType) == Type) { 241 Result.CommandLine.emplace_back(( 242 llvm::Twine(ClangCLMode ? "/std:" : "-std=") + 243 LangStandard::getLangStandardForKind(Std).getName()).str()); 244 } 245 Result.CommandLine.push_back("--"); 246 Result.CommandLine.push_back(std::string(Filename)); 247 return Result; 248 } 249 250 private: 251 // Map the language from the --std flag to that of the -x flag. 252 static types::ID toType(Language Lang) { 253 switch (Lang) { 254 case Language::C: 255 return types::TY_C; 256 case Language::CXX: 257 return types::TY_CXX; 258 case Language::ObjC: 259 return types::TY_ObjC; 260 case Language::ObjCXX: 261 return types::TY_ObjCXX; 262 default: 263 return types::TY_INVALID; 264 } 265 } 266 267 // Convert a file type to the matching CL-style type flag. 268 static StringRef toCLFlag(types::ID Type) { 269 switch (Type) { 270 case types::TY_C: 271 case types::TY_CHeader: 272 return "/TC"; 273 case types::TY_CXX: 274 case types::TY_CXXHeader: 275 return "/TP"; 276 default: 277 return StringRef(); 278 } 279 } 280 281 // Try to interpret the argument as a type specifier, e.g. '-x'. 282 std::optional<types::ID> tryParseTypeArg(const llvm::opt::Arg &Arg) { 283 const llvm::opt::Option &Opt = Arg.getOption(); 284 using namespace driver::options; 285 if (ClangCLMode) { 286 if (Opt.matches(OPT__SLASH_TC) || Opt.matches(OPT__SLASH_Tc)) 287 return types::TY_C; 288 if (Opt.matches(OPT__SLASH_TP) || Opt.matches(OPT__SLASH_Tp)) 289 return types::TY_CXX; 290 } else { 291 if (Opt.matches(driver::options::OPT_x)) 292 return types::lookupTypeForTypeSpecifier(Arg.getValue()); 293 } 294 return std::nullopt; 295 } 296 297 // Try to interpret the argument as '-std='. 298 std::optional<LangStandard::Kind> tryParseStdArg(const llvm::opt::Arg &Arg) { 299 using namespace driver::options; 300 if (Arg.getOption().matches(ClangCLMode ? OPT__SLASH_std : OPT_std_EQ)) 301 return LangStandard::getLangKind(Arg.getValue()); 302 return std::nullopt; 303 } 304 }; 305 306 // Given a filename, FileIndex picks the best matching file from the underlying 307 // DB. This is the proxy file whose CompileCommand will be reused. The 308 // heuristics incorporate file name, extension, and directory structure. 309 // Strategy: 310 // - Build indexes of each of the substrings we want to look up by. 311 // These indexes are just sorted lists of the substrings. 312 // - Each criterion corresponds to a range lookup into the index, so we only 313 // need O(log N) string comparisons to determine scores. 314 // 315 // Apart from path proximity signals, also takes file extensions into account 316 // when scoring the candidates. 317 class FileIndex { 318 public: 319 FileIndex(std::vector<std::string> Files) 320 : OriginalPaths(std::move(Files)), Strings(Arena) { 321 // Sort commands by filename for determinism (index is a tiebreaker later). 322 llvm::sort(OriginalPaths); 323 Paths.reserve(OriginalPaths.size()); 324 Types.reserve(OriginalPaths.size()); 325 Stems.reserve(OriginalPaths.size()); 326 for (size_t I = 0; I < OriginalPaths.size(); ++I) { 327 StringRef Path = Strings.save(StringRef(OriginalPaths[I]).lower()); 328 329 Paths.emplace_back(Path, I); 330 Types.push_back(foldType(guessType(OriginalPaths[I]))); 331 Stems.emplace_back(sys::path::stem(Path), I); 332 auto Dir = ++sys::path::rbegin(Path), DirEnd = sys::path::rend(Path); 333 for (int J = 0; J < DirectorySegmentsIndexed && Dir != DirEnd; ++J, ++Dir) 334 if (Dir->size() > ShortDirectorySegment) // not trivial ones 335 Components.emplace_back(*Dir, I); 336 } 337 llvm::sort(Paths); 338 llvm::sort(Stems); 339 llvm::sort(Components); 340 } 341 342 bool empty() const { return Paths.empty(); } 343 344 // Returns the path for the file that best fits OriginalFilename. 345 // Candidates with extensions matching PreferLanguage will be chosen over 346 // others (unless it's TY_INVALID, or all candidates are bad). 347 StringRef chooseProxy(StringRef OriginalFilename, 348 types::ID PreferLanguage) const { 349 assert(!empty() && "need at least one candidate!"); 350 std::string Filename = OriginalFilename.lower(); 351 auto Candidates = scoreCandidates(Filename); 352 std::pair<size_t, int> Best = 353 pickWinner(Candidates, Filename, PreferLanguage); 354 355 DEBUG_WITH_TYPE( 356 "interpolate", 357 llvm::dbgs() << "interpolate: chose " << OriginalPaths[Best.first] 358 << " as proxy for " << OriginalFilename << " preferring " 359 << (PreferLanguage == types::TY_INVALID 360 ? "none" 361 : types::getTypeName(PreferLanguage)) 362 << " score=" << Best.second << "\n"); 363 return OriginalPaths[Best.first]; 364 } 365 366 private: 367 using SubstringAndIndex = std::pair<StringRef, size_t>; 368 // Directory matching parameters: we look at the last two segments of the 369 // parent directory (usually the semantically significant ones in practice). 370 // We search only the last four of each candidate (for efficiency). 371 constexpr static int DirectorySegmentsIndexed = 4; 372 constexpr static int DirectorySegmentsQueried = 2; 373 constexpr static int ShortDirectorySegment = 1; // Only look at longer names. 374 375 // Award points to candidate entries that should be considered for the file. 376 // Returned keys are indexes into paths, and the values are (nonzero) scores. 377 DenseMap<size_t, int> scoreCandidates(StringRef Filename) const { 378 // Decompose Filename into the parts we care about. 379 // /some/path/complicated/project/Interesting.h 380 // [-prefix--][---dir---] [-dir-] [--stem---] 381 StringRef Stem = sys::path::stem(Filename); 382 llvm::SmallVector<StringRef, DirectorySegmentsQueried> Dirs; 383 llvm::StringRef Prefix; 384 auto Dir = ++sys::path::rbegin(Filename), 385 DirEnd = sys::path::rend(Filename); 386 for (int I = 0; I < DirectorySegmentsQueried && Dir != DirEnd; ++I, ++Dir) { 387 if (Dir->size() > ShortDirectorySegment) 388 Dirs.push_back(*Dir); 389 Prefix = Filename.substr(0, Dir - DirEnd); 390 } 391 392 // Now award points based on lookups into our various indexes. 393 DenseMap<size_t, int> Candidates; // Index -> score. 394 auto Award = [&](int Points, ArrayRef<SubstringAndIndex> Range) { 395 for (const auto &Entry : Range) 396 Candidates[Entry.second] += Points; 397 }; 398 // Award one point if the file's basename is a prefix of the candidate, 399 // and another if it's an exact match (so exact matches get two points). 400 Award(1, indexLookup</*Prefix=*/true>(Stem, Stems)); 401 Award(1, indexLookup</*Prefix=*/false>(Stem, Stems)); 402 // For each of the last few directories in the Filename, award a point 403 // if it's present in the candidate. 404 for (StringRef Dir : Dirs) 405 Award(1, indexLookup</*Prefix=*/false>(Dir, Components)); 406 // Award one more point if the whole rest of the path matches. 407 if (sys::path::root_directory(Prefix) != Prefix) 408 Award(1, indexLookup</*Prefix=*/true>(Prefix, Paths)); 409 return Candidates; 410 } 411 412 // Pick a single winner from the set of scored candidates. 413 // Returns (index, score). 414 std::pair<size_t, int> pickWinner(const DenseMap<size_t, int> &Candidates, 415 StringRef Filename, 416 types::ID PreferredLanguage) const { 417 struct ScoredCandidate { 418 size_t Index; 419 bool Preferred; 420 int Points; 421 size_t PrefixLength; 422 }; 423 // Choose the best candidate by (preferred, points, prefix length, alpha). 424 ScoredCandidate Best = {size_t(-1), false, 0, 0}; 425 for (const auto &Candidate : Candidates) { 426 ScoredCandidate S; 427 S.Index = Candidate.first; 428 S.Preferred = PreferredLanguage == types::TY_INVALID || 429 PreferredLanguage == Types[S.Index]; 430 S.Points = Candidate.second; 431 if (!S.Preferred && Best.Preferred) 432 continue; 433 if (S.Preferred == Best.Preferred) { 434 if (S.Points < Best.Points) 435 continue; 436 if (S.Points == Best.Points) { 437 S.PrefixLength = matchingPrefix(Filename, Paths[S.Index].first); 438 if (S.PrefixLength < Best.PrefixLength) 439 continue; 440 // hidden heuristics should at least be deterministic! 441 if (S.PrefixLength == Best.PrefixLength) 442 if (S.Index > Best.Index) 443 continue; 444 } 445 } 446 // PrefixLength was only set above if actually needed for a tiebreak. 447 // But it definitely needs to be set to break ties in the future. 448 S.PrefixLength = matchingPrefix(Filename, Paths[S.Index].first); 449 Best = S; 450 } 451 // Edge case: no candidate got any points. 452 // We ignore PreferredLanguage at this point (not ideal). 453 if (Best.Index == size_t(-1)) 454 return {longestMatch(Filename, Paths).second, 0}; 455 return {Best.Index, Best.Points}; 456 } 457 458 // Returns the range within a sorted index that compares equal to Key. 459 // If Prefix is true, it's instead the range starting with Key. 460 template <bool Prefix> 461 ArrayRef<SubstringAndIndex> 462 indexLookup(StringRef Key, ArrayRef<SubstringAndIndex> Idx) const { 463 // Use pointers as iteratiors to ease conversion of result to ArrayRef. 464 auto Range = std::equal_range(Idx.data(), Idx.data() + Idx.size(), Key, 465 Less<Prefix>()); 466 return {Range.first, Range.second}; 467 } 468 469 // Performs a point lookup into a nonempty index, returning a longest match. 470 SubstringAndIndex longestMatch(StringRef Key, 471 ArrayRef<SubstringAndIndex> Idx) const { 472 assert(!Idx.empty()); 473 // Longest substring match will be adjacent to a direct lookup. 474 auto It = llvm::lower_bound(Idx, SubstringAndIndex{Key, 0}); 475 if (It == Idx.begin()) 476 return *It; 477 if (It == Idx.end()) 478 return *--It; 479 // Have to choose between It and It-1 480 size_t Prefix = matchingPrefix(Key, It->first); 481 size_t PrevPrefix = matchingPrefix(Key, (It - 1)->first); 482 return Prefix > PrevPrefix ? *It : *--It; 483 } 484 485 // Original paths, everything else is in lowercase. 486 std::vector<std::string> OriginalPaths; 487 BumpPtrAllocator Arena; 488 StringSaver Strings; 489 // Indexes of candidates by certain substrings. 490 // String is lowercase and sorted, index points into OriginalPaths. 491 std::vector<SubstringAndIndex> Paths; // Full path. 492 // Lang types obtained by guessing on the corresponding path. I-th element is 493 // a type for the I-th path. 494 std::vector<types::ID> Types; 495 std::vector<SubstringAndIndex> Stems; // Basename, without extension. 496 std::vector<SubstringAndIndex> Components; // Last path components. 497 }; 498 499 // The actual CompilationDatabase wrapper delegates to its inner database. 500 // If no match, looks up a proxy file in FileIndex and transfers its 501 // command to the requested file. 502 class InterpolatingCompilationDatabase : public CompilationDatabase { 503 public: 504 InterpolatingCompilationDatabase(std::unique_ptr<CompilationDatabase> Inner) 505 : Inner(std::move(Inner)), Index(this->Inner->getAllFiles()) {} 506 507 std::vector<CompileCommand> 508 getCompileCommands(StringRef Filename) const override { 509 auto Known = Inner->getCompileCommands(Filename); 510 if (Index.empty() || !Known.empty()) 511 return Known; 512 bool TypeCertain; 513 auto Lang = guessType(Filename, &TypeCertain); 514 if (!TypeCertain) 515 Lang = types::TY_INVALID; 516 auto ProxyCommands = 517 Inner->getCompileCommands(Index.chooseProxy(Filename, foldType(Lang))); 518 if (ProxyCommands.empty()) 519 return {}; 520 return {transferCompileCommand(std::move(ProxyCommands.front()), Filename)}; 521 } 522 523 std::vector<std::string> getAllFiles() const override { 524 return Inner->getAllFiles(); 525 } 526 527 std::vector<CompileCommand> getAllCompileCommands() const override { 528 return Inner->getAllCompileCommands(); 529 } 530 531 private: 532 std::unique_ptr<CompilationDatabase> Inner; 533 FileIndex Index; 534 }; 535 536 } // namespace 537 538 std::unique_ptr<CompilationDatabase> 539 inferMissingCompileCommands(std::unique_ptr<CompilationDatabase> Inner) { 540 return std::make_unique<InterpolatingCompilationDatabase>(std::move(Inner)); 541 } 542 543 tooling::CompileCommand transferCompileCommand(CompileCommand Cmd, 544 StringRef Filename) { 545 return TransferableCommand(std::move(Cmd)).transferTo(Filename); 546 } 547 548 } // namespace tooling 549 } // namespace clang 550