clang-tools-extra/clangd/CompileCommands.cpp

   1 //===--- CompileCommands.cpp ----------------------------------------------===//
   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 #include "CompileCommands.h"
  10 #include "Config.h"
  11 #include "support/Logger.h"
  12 #include "support/Trace.h"
  13 #include "clang/Driver/Driver.h"
  14 #include "clang/Driver/Options.h"
  15 #include "clang/Frontend/CompilerInvocation.h"
  16 #include "clang/Tooling/CompilationDatabase.h"
  17 #include "clang/Tooling/Tooling.h"
  18 #include "llvm/ADT/ArrayRef.h"
  19 #include "llvm/ADT/STLExtras.h"
  20 #include "llvm/ADT/SmallVector.h"
  21 #include "llvm/ADT/StringRef.h"
  22 #include "llvm/Option/ArgList.h"
  23 #include "llvm/Option/Option.h"
  24 #include "llvm/Support/Allocator.h"
  25 #include "llvm/Support/Debug.h"
  26 #include "llvm/Support/FileSystem.h"
  27 #include "llvm/Support/FileUtilities.h"
  28 #include "llvm/Support/MemoryBuffer.h"
  29 #include "llvm/Support/Path.h"
  30 #include "llvm/Support/Program.h"
  31 #include <iterator>
  32 #include <optional>
  33 #include <string>
  34 #include <vector>
  35
  36 namespace clang {
  37 namespace clangd {
  38 namespace {
  39
  40 // Query apple's `xcrun` launcher, which is the source of truth for "how should"
  41 // clang be invoked on this system.
  42 std::optional<std::string> queryXcrun(llvm::ArrayRef<llvm::StringRef> Argv) {
  43   auto Xcrun = llvm::sys::findProgramByName("xcrun");
  44   if (!Xcrun) {
  45     log("Couldn't find xcrun. Hopefully you have a non-apple toolchain...");
  46     return std::nullopt;
  47   }
  48   llvm::SmallString<64> OutFile;
  49   llvm::sys::fs::createTemporaryFile("clangd-xcrun", "", OutFile);
  50   llvm::FileRemover OutRemover(OutFile);
  51   std::optional<llvm::StringRef> Redirects[3] = {
  52       /*stdin=*/{""}, /*stdout=*/{OutFile.str()}, /*stderr=*/{""}};
  53   vlog("Invoking {0} to find clang installation", *Xcrun);
  54   int Ret = llvm::sys::ExecuteAndWait(*Xcrun, Argv,
  55                                       /*Env=*/std::nullopt, Redirects,
  56                                       /*SecondsToWait=*/10);
  57   if (Ret != 0) {
  58     log("xcrun exists but failed with code {0}. "
  59         "If you have a non-apple toolchain, this is OK. "
  60         "Otherwise, try xcode-select --install.",
  61         Ret);
  62     return std::nullopt;
  63   }
  64
  65   auto Buf = llvm::MemoryBuffer::getFile(OutFile);
  66   if (!Buf) {
  67     log("Can't read xcrun output: {0}", Buf.getError().message());
  68     return std::nullopt;
  69   }
  70   StringRef Path = Buf->get()->getBuffer().trim();
  71   if (Path.empty()) {
  72     log("xcrun produced no output");
  73     return std::nullopt;
  74   }
  75   return Path.str();
  76 }
  77
  78 // Resolve symlinks if possible.
  79 std::string resolve(std::string Path) {
  80   llvm::SmallString<128> Resolved;
  81   if (llvm::sys::fs::real_path(Path, Resolved)) {
  82     log("Failed to resolve possible symlink {0}", Path);
  83     return Path;
  84   }
  85   return std::string(Resolved);
  86 }
  87
  88 // Get a plausible full `clang` path.
  89 // This is used in the fallback compile command, or when the CDB returns a
  90 // generic driver with no path.
  91 std::string detectClangPath() {
  92   // The driver and/or cc1 sometimes depend on the binary name to compute
  93   // useful things like the standard library location.
  94   // We need to emulate what clang on this system is likely to see.
  95   // cc1 in particular looks at the "real path" of the running process, and
  96   // so if /usr/bin/clang is a symlink, it sees the resolved path.
  97   // clangd doesn't have that luxury, so we resolve symlinks ourselves.
  98
  99   // On Mac, `which clang` is /usr/bin/clang. It runs `xcrun clang`, which knows
 100   // where the real clang is kept. We need to do the same thing,
 101   // because cc1 (not the driver!) will find libc++ relative to argv[0].
 102 #ifdef __APPLE__
 103   if (auto MacClang = queryXcrun({"xcrun", "--find", "clang"}))
 104     return resolve(std::move(*MacClang));
 105 #endif
 106   // On other platforms, just look for compilers on the PATH.
 107   for (const char *Name : {"clang", "gcc", "cc"})
 108     if (auto PathCC = llvm::sys::findProgramByName(Name))
 109       return resolve(std::move(*PathCC));
 110   // Fallback: a nonexistent 'clang' binary next to clangd.
 111   static int StaticForMainAddr;
 112   std::string ClangdExecutable =
 113       llvm::sys::fs::getMainExecutable("clangd", (void *)&StaticForMainAddr);
 114   SmallString<128> ClangPath;
 115   ClangPath = llvm::sys::path::parent_path(ClangdExecutable);
 116   llvm::sys::path::append(ClangPath, "clang");
 117   return std::string(ClangPath);
 118 }
 119
 120 // On mac, /usr/bin/clang sets SDKROOT and then invokes the real clang.
 121 // The effect of this is to set -isysroot correctly. We do the same.
 122 std::optional<std::string> detectSysroot() {
 123 #ifndef __APPLE__
 124   return std::nullopt;
 125 #endif
 126
 127   // SDKROOT overridden in environment, respect it. Driver will set isysroot.
 128   if (::getenv("SDKROOT"))
 129     return std::nullopt;
 130   return queryXcrun({"xcrun", "--show-sdk-path"});
 131 }
 132
 133 std::string detectStandardResourceDir() {
 134   static int StaticForMainAddr; // Just an address in this process.
 135   return CompilerInvocation::GetResourcesPath("clangd",
 136                                               (void *)&StaticForMainAddr);
 137 }
 138
 139 // The path passed to argv[0] is important:
 140 //  - its parent directory is Driver::Dir, used for library discovery
 141 //  - its basename affects CLI parsing (clang-cl) and other settings
 142 // Where possible it should be an absolute path with sensible directory, but
 143 // with the original basename.
 144 static std::string resolveDriver(llvm::StringRef Driver, bool FollowSymlink,
 145                                  std::optional<std::string> ClangPath) {
 146   auto SiblingOf = [&](llvm::StringRef AbsPath) {
 147     llvm::SmallString<128> Result = llvm::sys::path::parent_path(AbsPath);
 148     llvm::sys::path::append(Result, llvm::sys::path::filename(Driver));
 149     return Result.str().str();
 150   };
 151
 152   // First, eliminate relative paths.
 153   std::string Storage;
 154   if (!llvm::sys::path::is_absolute(Driver)) {
 155     // If it's working-dir relative like bin/clang, we can't resolve it.
 156     // FIXME: we could if we had the working directory here.
 157     // Let's hope it's not a symlink.
 158     if (llvm::any_of(Driver,
 159                      [](char C) { return llvm::sys::path::is_separator(C); }))
 160       return Driver.str();
 161     // If the driver is a generic like "g++" with no path, add clang dir.
 162     if (ClangPath &&
 163         (Driver == "clang" || Driver == "clang++" || Driver == "gcc" ||
 164          Driver == "g++" || Driver == "cc" || Driver == "c++")) {
 165       return SiblingOf(*ClangPath);
 166     }
 167     // Otherwise try to look it up on PATH. This won't change basename.
 168     auto Absolute = llvm::sys::findProgramByName(Driver);
 169     if (Absolute && llvm::sys::path::is_absolute(*Absolute))
 170       Driver = Storage = std::move(*Absolute);
 171     else if (ClangPath) // If we don't find it, use clang dir again.
 172       return SiblingOf(*ClangPath);
 173     else // Nothing to do: can't find the command and no detected dir.
 174       return Driver.str();
 175   }
 176
 177   // Now we have an absolute path, but it may be a symlink.
 178   assert(llvm::sys::path::is_absolute(Driver));
 179   if (FollowSymlink) {
 180     llvm::SmallString<256> Resolved;
 181     if (!llvm::sys::fs::real_path(Driver, Resolved))
 182       return SiblingOf(Resolved);
 183   }
 184   return Driver.str();
 185 }
 186
 187 } // namespace
 188
 189 CommandMangler CommandMangler::detect() {
 190   CommandMangler Result;
 191   Result.ClangPath = detectClangPath();
 192   Result.ResourceDir = detectStandardResourceDir();
 193   Result.Sysroot = detectSysroot();
 194   return Result;
 195 }
 196
 197 CommandMangler CommandMangler::forTests() { return CommandMangler(); }
 198
 199 void CommandMangler::operator()(tooling::CompileCommand &Command,
 200                                 llvm::StringRef File) const {
 201   std::vector<std::string> &Cmd = Command.CommandLine;
 202   trace::Span S("AdjustCompileFlags");
 203   // Most of the modifications below assumes the Cmd starts with a driver name.
 204   // We might consider injecting a generic driver name like "cc" or "c++", but
 205   // a Cmd missing the driver is probably rare enough in practice and erroneous.
 206   if (Cmd.empty())
 207     return;
 208
 209   auto &OptTable = clang::driver::getDriverOptTable();
 210   // OriginalArgs needs to outlive ArgList.
 211   llvm::SmallVector<const char *, 16> OriginalArgs;
 212   OriginalArgs.reserve(Cmd.size());
 213   for (const auto &S : Cmd)
 214     OriginalArgs.push_back(S.c_str());
 215   bool IsCLMode = driver::IsClangCL(driver::getDriverMode(
 216       OriginalArgs[0], llvm::ArrayRef(OriginalArgs).slice(1)));
 217   // ParseArgs propagates missing arg/opt counts on error, but preserves
 218   // everything it could parse in ArgList. So we just ignore those counts.
 219   unsigned IgnoredCount;
 220   // Drop the executable name, as ParseArgs doesn't expect it. This means
 221   // indices are actually of by one between ArgList and OriginalArgs.
 222   llvm::opt::InputArgList ArgList;
 223   ArgList = OptTable.ParseArgs(
 224       llvm::ArrayRef(OriginalArgs).drop_front(), IgnoredCount, IgnoredCount,
 225       llvm::opt::Visibility(IsCLMode ? driver::options::CLOption
 226                                      : driver::options::ClangOption));
 227
 228   llvm::SmallVector<unsigned, 1> IndicesToDrop;
 229   // Having multiple architecture options (e.g. when building fat binaries)
 230   // results in multiple compiler jobs, which clangd cannot handle. In such
 231   // cases strip all the `-arch` options and fallback to default architecture.
 232   // As there are no signals to figure out which one user actually wants. They
 233   // can explicitly specify one through `CompileFlags.Add` if need be.
 234   unsigned ArchOptCount = 0;
 235   for (auto *Input : ArgList.filtered(driver::options::OPT_arch)) {
 236     ++ArchOptCount;
 237     for (auto I = 0U; I <= Input->getNumValues(); ++I)
 238       IndicesToDrop.push_back(Input->getIndex() + I);
 239   }
 240   // If there is a single `-arch` option, keep it.
 241   if (ArchOptCount < 2)
 242     IndicesToDrop.clear();
 243
 244   // In some cases people may try to reuse the command from another file, e.g.
 245   //   { File: "foo.h", CommandLine: "clang foo.cpp" }.
 246   // We assume the intent is to parse foo.h the same way as foo.cpp, or as if
 247   // it were being included from foo.cpp.
 248   //
 249   // We're going to rewrite the command to refer to foo.h, and this may change
 250   // its semantics (e.g. by parsing the file as C). If we do this, we should
 251   // use transferCompileCommand to adjust the argv.
 252   // In practice only the extension of the file matters, so do this only when
 253   // it differs.
 254   llvm::StringRef FileExtension = llvm::sys::path::extension(File);
 255   std::optional<std::string> TransferFrom;
 256   auto SawInput = [&](llvm::StringRef Input) {
 257     if (llvm::sys::path::extension(Input) != FileExtension)
 258       TransferFrom.emplace(Input);
 259   };
 260
 261   // Strip all the inputs and `--`. We'll put the input for the requested file
 262   // explicitly at the end of the flags. This ensures modifications done in the
 263   // following steps apply in more cases (like setting -x, which only affects
 264   // inputs that come after it).
 265   for (auto *Input : ArgList.filtered(driver::options::OPT_INPUT)) {
 266     SawInput(Input->getValue(0));
 267     IndicesToDrop.push_back(Input->getIndex());
 268   }
 269   // Anything after `--` is also treated as input, drop them as well.
 270   if (auto *DashDash =
 271           ArgList.getLastArgNoClaim(driver::options::OPT__DASH_DASH)) {
 272     auto DashDashIndex = DashDash->getIndex() + 1; // +1 accounts for Cmd[0]
 273     for (unsigned I = DashDashIndex; I < Cmd.size(); ++I)
 274       SawInput(Cmd[I]);
 275     Cmd.resize(DashDashIndex);
 276   }
 277   llvm::sort(IndicesToDrop);
 278   for (unsigned Idx : llvm::reverse(IndicesToDrop))
 279     // +1 to account for the executable name in Cmd[0] that
 280     // doesn't exist in ArgList.
 281     Cmd.erase(Cmd.begin() + Idx + 1);
 282   // All the inputs are stripped, append the name for the requested file. Rest
 283   // of the modifications should respect `--`.
 284   Cmd.push_back("--");
 285   Cmd.push_back(File.str());
 286
 287   if (TransferFrom) {
 288     tooling::CompileCommand TransferCmd;
 289     TransferCmd.Filename = std::move(*TransferFrom);
 290     TransferCmd.CommandLine = std::move(Cmd);
 291     TransferCmd = transferCompileCommand(std::move(TransferCmd), File);
 292     Cmd = std::move(TransferCmd.CommandLine);
 293     assert(Cmd.size() >= 2 && Cmd.back() == File &&
 294            Cmd[Cmd.size() - 2] == "--" &&
 295            "TransferCommand should produce a command ending in -- filename");
 296   }
 297
 298   for (auto &Edit : Config::current().CompileFlags.Edits)
 299     Edit(Cmd);
 300
 301   // The system include extractor needs to run:
 302   //  - AFTER transferCompileCommand(), because the -x flag it adds may be
 303   //    necessary for the system include extractor to identify the file type
 304   //  - AFTER applying CompileFlags.Edits, because the name of the compiler
 305   //    that needs to be invoked may come from the CompileFlags->Compiler key
 306   //  - BEFORE addTargetAndModeForProgramName(), because gcc doesn't support
 307   //    the target flag that might be added.
 308   //  - BEFORE resolveDriver() because that can mess up the driver path,
 309   //    e.g. changing gcc to /path/to/clang/bin/gcc
 310   if (SystemIncludeExtractor) {
 311     SystemIncludeExtractor(Command, File);
 312   }
 313
 314   tooling::addTargetAndModeForProgramName(Cmd, Cmd.front());
 315
 316   // Check whether the flag exists in the command.
 317   auto HasExact = [&](llvm::StringRef Flag) {
 318     return llvm::any_of(Cmd, [&](llvm::StringRef Arg) { return Arg == Flag; });
 319   };
 320
 321   // Check whether the flag appears in the command as a prefix.
 322   auto HasPrefix = [&](llvm::StringRef Flag) {
 323     return llvm::any_of(
 324         Cmd, [&](llvm::StringRef Arg) { return Arg.starts_with(Flag); });
 325   };
 326
 327   llvm::erase_if(Cmd, [](llvm::StringRef Elem) {
 328     return Elem.starts_with("--save-temps") || Elem.starts_with("-save-temps");
 329   });
 330
 331   std::vector<std::string> ToAppend;
 332   if (ResourceDir && !HasExact("-resource-dir") && !HasPrefix("-resource-dir="))
 333     ToAppend.push_back(("-resource-dir=" + *ResourceDir));
 334
 335   // Don't set `-isysroot` if it is already set or if `--sysroot` is set.
 336   // `--sysroot` is a superset of the `-isysroot` argument.
 337   if (Sysroot && !HasPrefix("-isysroot") && !HasExact("--sysroot") &&
 338       !HasPrefix("--sysroot=")) {
 339     ToAppend.push_back("-isysroot");
 340     ToAppend.push_back(*Sysroot);
 341   }
 342
 343   if (!ToAppend.empty()) {
 344     Cmd.insert(llvm::find(Cmd, "--"), std::make_move_iterator(ToAppend.begin()),
 345                std::make_move_iterator(ToAppend.end()));
 346   }
 347
 348   if (!Cmd.empty()) {
 349     bool FollowSymlink = !HasExact("-no-canonical-prefixes");
 350     Cmd.front() =
 351         (FollowSymlink ? ResolvedDrivers : ResolvedDriversNoFollow)
 352             .get(Cmd.front(), [&, this] {
 353               return resolveDriver(Cmd.front(), FollowSymlink, ClangPath);
 354             });
 355   }
 356 }
 357
 358 // ArgStripper implementation
 359 namespace {
 360
 361 // Determine total number of args consumed by this option.
 362 // Return answers for {Exact, Prefix} match. 0 means not allowed.
 363 std::pair<unsigned, unsigned> getArgCount(const llvm::opt::Option &Opt) {
 364   constexpr static unsigned Rest = 10000; // Should be all the rest!
 365   // Reference is llvm::opt::Option::acceptInternal()
 366   using llvm::opt::Option;
 367   switch (Opt.getKind()) {
 368   case Option::FlagClass:
 369     return {1, 0};
 370   case Option::JoinedClass:
 371   case Option::CommaJoinedClass:
 372     return {1, 1};
 373   case Option::GroupClass:
 374   case Option::InputClass:
 375   case Option::UnknownClass:
 376   case Option::ValuesClass:
 377     return {1, 0};
 378   case Option::JoinedAndSeparateClass:
 379     return {2, 2};
 380   case Option::SeparateClass:
 381     return {2, 0};
 382   case Option::MultiArgClass:
 383     return {1 + Opt.getNumArgs(), 0};
 384   case Option::JoinedOrSeparateClass:
 385     return {2, 1};
 386   case Option::RemainingArgsClass:
 387     return {Rest, 0};
 388   case Option::RemainingArgsJoinedClass:
 389     return {Rest, Rest};
 390   }
 391   llvm_unreachable("Unhandled option kind");
 392 }
 393
 394 // Flag-parsing mode, which affects which flags are available.
 395 enum DriverMode : unsigned char {
 396   DM_None = 0,
 397   DM_GCC = 1, // Default mode e.g. when invoked as 'clang'
 398   DM_CL = 2,  // MS CL.exe compatible mode e.g. when invoked as 'clang-cl'
 399   DM_CC1 = 4, // When invoked as 'clang -cc1' or after '-Xclang'
 400   DM_All = 7
 401 };
 402
 403 // Examine args list to determine if we're in GCC, CL-compatible, or cc1 mode.
 404 DriverMode getDriverMode(const std::vector<std::string> &Args) {
 405   DriverMode Mode = DM_GCC;
 406   llvm::StringRef Argv0 = Args.front();
 407   if (Argv0.ends_with_insensitive(".exe"))
 408     Argv0 = Argv0.drop_back(strlen(".exe"));
 409   if (Argv0.ends_with_insensitive("cl"))
 410     Mode = DM_CL;
 411   for (const llvm::StringRef Arg : Args) {
 412     if (Arg == "--driver-mode=cl") {
 413       Mode = DM_CL;
 414       break;
 415     }
 416     if (Arg == "-cc1") {
 417       Mode = DM_CC1;
 418       break;
 419     }
 420   }
 421   return Mode;
 422 }
 423
 424 // Returns the set of DriverModes where an option may be used.
 425 unsigned char getModes(const llvm::opt::Option &Opt) {
 426   unsigned char Result = DM_None;
 427   if (Opt.hasVisibilityFlag(driver::options::ClangOption))
 428     Result |= DM_GCC;
 429   if (Opt.hasVisibilityFlag(driver::options::CC1Option))
 430     Result |= DM_CC1;
 431   if (Opt.hasVisibilityFlag(driver::options::CLOption))
 432     Result |= DM_CL;
 433   return Result;
 434 }
 435
 436 } // namespace
 437
 438 llvm::ArrayRef<ArgStripper::Rule> ArgStripper::rulesFor(llvm::StringRef Arg) {
 439   // All the hard work is done once in a static initializer.
 440   // We compute a table containing strings to look for and #args to skip.
 441   // e.g. "-x" => {-x 2 args, -x* 1 arg, --language 2 args, --language=* 1 arg}
 442   using TableTy =
 443       llvm::StringMap<llvm::SmallVector<Rule, 4>, llvm::BumpPtrAllocator>;
 444   static TableTy *Table = [] {
 445     auto &DriverTable = driver::getDriverOptTable();
 446     using DriverID = clang::driver::options::ID;
 447
 448     // Collect sets of aliases, so we can treat -foo and -foo= as synonyms.
 449     // Conceptually a double-linked list: PrevAlias[I] -> I -> NextAlias[I].
 450     // If PrevAlias[I] is INVALID, then I is canonical.
 451     DriverID PrevAlias[DriverID::LastOption] = {DriverID::OPT_INVALID};
 452     DriverID NextAlias[DriverID::LastOption] = {DriverID::OPT_INVALID};
 453     auto AddAlias = [&](DriverID Self, DriverID T) {
 454       if (NextAlias[T]) {
 455         PrevAlias[NextAlias[T]] = Self;
 456         NextAlias[Self] = NextAlias[T];
 457       }
 458       PrevAlias[Self] = T;
 459       NextAlias[T] = Self;
 460     };
 461     // Also grab prefixes for each option, these are not fully exposed.
 462     llvm::ArrayRef<llvm::StringLiteral> Prefixes[DriverID::LastOption];
 463
 464 #define PREFIX(NAME, VALUE)                                                    \
 465   static constexpr llvm::StringLiteral NAME##_init[] = VALUE;                  \
 466   static constexpr llvm::ArrayRef<llvm::StringLiteral> NAME(                   \
 467       NAME##_init, std::size(NAME##_init) - 1);
 468 #define OPTION(PREFIX, PREFIXED_NAME, ID, KIND, GROUP, ALIAS, ALIASARGS,       \
 469                FLAGS, VISIBILITY, PARAM, HELPTEXT, HELPTEXTSFORVARIANTS,       \
 470                METAVAR, VALUES)                                                \
 471   Prefixes[DriverID::OPT_##ID] = PREFIX;
 472 #include "clang/Driver/Options.inc"
 473 #undef OPTION
 474 #undef PREFIX
 475
 476     struct {
 477       DriverID ID;
 478       DriverID AliasID;
 479       const void *AliasArgs;
 480     } AliasTable[] = {
 481 #define OPTION(PREFIX, PREFIXED_NAME, ID, KIND, GROUP, ALIAS, ALIASARGS,       \
 482                FLAGS, VISIBILITY, PARAM, HELPTEXT, HELPTEXTSFORVARIANTS,       \
 483                METAVAR, VALUES)                                                \
 484   {DriverID::OPT_##ID, DriverID::OPT_##ALIAS, ALIASARGS},
 485 #include "clang/Driver/Options.inc"
 486 #undef OPTION
 487     };
 488     for (auto &E : AliasTable)
 489       if (E.AliasID != DriverID::OPT_INVALID && E.AliasArgs == nullptr)
 490         AddAlias(E.ID, E.AliasID);
 491
 492     auto Result = std::make_unique<TableTy>();
 493     // Iterate over distinct options (represented by the canonical alias).
 494     // Every spelling of this option will get the same set of rules.
 495     for (unsigned ID = 1 /*Skip INVALID */; ID < DriverID::LastOption; ++ID) {
 496       if (PrevAlias[ID] || ID == DriverID::OPT_Xclang)
 497         continue; // Not canonical, or specially handled.
 498       llvm::SmallVector<Rule> Rules;
 499       // Iterate over each alias, to add rules for parsing it.
 500       for (unsigned A = ID; A != DriverID::OPT_INVALID; A = NextAlias[A]) {
 501         if (!Prefixes[A].size()) // option groups.
 502           continue;
 503         auto Opt = DriverTable.getOption(A);
 504         // Exclude - and -foo pseudo-options.
 505         if (Opt.getName().empty())
 506           continue;
 507         auto Modes = getModes(Opt);
 508         std::pair<unsigned, unsigned> ArgCount = getArgCount(Opt);
 509         // Iterate over each spelling of the alias, e.g. -foo vs --foo.
 510         for (StringRef Prefix : Prefixes[A]) {
 511           llvm::SmallString<64> Buf(Prefix);
 512           Buf.append(Opt.getName());
 513           llvm::StringRef Spelling = Result->try_emplace(Buf).first->getKey();
 514           Rules.emplace_back();
 515           Rule &R = Rules.back();
 516           R.Text = Spelling;
 517           R.Modes = Modes;
 518           R.ExactArgs = ArgCount.first;
 519           R.PrefixArgs = ArgCount.second;
 520           // Concrete priority is the index into the option table.
 521           // Effectively, earlier entries take priority over later ones.
 522           assert(ID < std::numeric_limits<decltype(R.Priority)>::max() &&
 523                  "Rules::Priority overflowed by options table");
 524           R.Priority = ID;
 525         }
 526       }
 527       // Register the set of rules under each possible name.
 528       for (const auto &R : Rules)
 529         Result->find(R.Text)->second.append(Rules.begin(), Rules.end());
 530     }
 531 #ifndef NDEBUG
 532     // Dump the table and various measures of its size.
 533     unsigned RuleCount = 0;
 534     dlog("ArgStripper Option spelling table");
 535     for (const auto &Entry : *Result) {
 536       dlog("{0}", Entry.first());
 537       RuleCount += Entry.second.size();
 538       for (const auto &R : Entry.second)
 539         dlog("  {0} #={1} *={2} Mode={3}", R.Text, R.ExactArgs, R.PrefixArgs,
 540              int(R.Modes));
 541     }
 542     dlog("Table spellings={0} rules={1} string-bytes={2}", Result->size(),
 543          RuleCount, Result->getAllocator().getBytesAllocated());
 544 #endif
 545     // The static table will never be destroyed.
 546     return Result.release();
 547   }();
 548
 549   auto It = Table->find(Arg);
 550   return (It == Table->end()) ? llvm::ArrayRef<Rule>() : It->second;
 551 }
 552
 553 void ArgStripper::strip(llvm::StringRef Arg) {
 554   auto OptionRules = rulesFor(Arg);
 555   if (OptionRules.empty()) {
 556     // Not a recognized flag. Strip it literally.
 557     Storage.emplace_back(Arg);
 558     Rules.emplace_back();
 559     Rules.back().Text = Storage.back();
 560     Rules.back().ExactArgs = 1;
 561     if (Rules.back().Text.consume_back("*"))
 562       Rules.back().PrefixArgs = 1;
 563     Rules.back().Modes = DM_All;
 564     Rules.back().Priority = -1; // Max unsigned = lowest priority.
 565   } else {
 566     Rules.append(OptionRules.begin(), OptionRules.end());
 567   }
 568 }
 569
 570 const ArgStripper::Rule *ArgStripper::matchingRule(llvm::StringRef Arg,
 571                                                    unsigned Mode,
 572                                                    unsigned &ArgCount) const {
 573   const ArgStripper::Rule *BestRule = nullptr;
 574   for (const Rule &R : Rules) {
 575     // Rule can fail to match if...
 576     if (!(R.Modes & Mode))
 577       continue; // not applicable to current driver mode
 578     if (BestRule && BestRule->Priority < R.Priority)
 579       continue; // lower-priority than best candidate.
 580     if (!Arg.starts_with(R.Text))
 581       continue; // current arg doesn't match the prefix string
 582     bool PrefixMatch = Arg.size() > R.Text.size();
 583     // Can rule apply as an exact/prefix match?
 584     if (unsigned Count = PrefixMatch ? R.PrefixArgs : R.ExactArgs) {
 585       BestRule = &R;
 586       ArgCount = Count;
 587     }
 588     // Continue in case we find a higher-priority rule.
 589   }
 590   return BestRule;
 591 }
 592
 593 void ArgStripper::process(std::vector<std::string> &Args) const {
 594   if (Args.empty())
 595     return;
 596
 597   // We're parsing the args list in some mode (e.g. gcc-compatible) but may
 598   // temporarily switch to another mode with the -Xclang flag.
 599   DriverMode MainMode = getDriverMode(Args);
 600   DriverMode CurrentMode = MainMode;
 601
 602   // Read and write heads for in-place deletion.
 603   unsigned Read = 0, Write = 0;
 604   bool WasXclang = false;
 605   while (Read < Args.size()) {
 606     unsigned ArgCount = 0;
 607     if (matchingRule(Args[Read], CurrentMode, ArgCount)) {
 608       // Delete it and its args.
 609       if (WasXclang) {
 610         assert(Write > 0);
 611         --Write; // Drop previous -Xclang arg
 612         CurrentMode = MainMode;
 613         WasXclang = false;
 614       }
 615       // Advance to last arg. An arg may be foo or -Xclang foo.
 616       for (unsigned I = 1; Read < Args.size() && I < ArgCount; ++I) {
 617         ++Read;
 618         if (Read < Args.size() && Args[Read] == "-Xclang")
 619           ++Read;
 620       }
 621     } else {
 622       // No match, just copy the arg through.
 623       WasXclang = Args[Read] == "-Xclang";
 624       CurrentMode = WasXclang ? DM_CC1 : MainMode;
 625       if (Write != Read)
 626         Args[Write] = std::move(Args[Read]);
 627       ++Write;
 628     }
 629     ++Read;
 630   }
 631   Args.resize(Write);
 632 }
 633
 634 std::string printArgv(llvm::ArrayRef<llvm::StringRef> Args) {
 635   std::string Buf;
 636   llvm::raw_string_ostream OS(Buf);
 637   bool Sep = false;
 638   for (llvm::StringRef Arg : Args) {
 639     if (Sep)
 640       OS << ' ';
 641     Sep = true;
 642     if (llvm::all_of(Arg, llvm::isPrint) &&
 643         Arg.find_first_of(" \t\n\"\\") == llvm::StringRef::npos) {
 644       OS << Arg;
 645       continue;
 646     }
 647     OS << '"';
 648     OS.write_escaped(Arg, /*UseHexEscapes=*/true);
 649     OS << '"';
 650   }
 651   return std::move(OS.str());
 652 }
 653
 654 std::string printArgv(llvm::ArrayRef<std::string> Args) {
 655   std::vector<llvm::StringRef> Refs(Args.size());
 656   llvm::copy(Args, Refs.begin());
 657   return printArgv(Refs);
 658 }
 659
 660 } // namespace clangd
 661 } // namespace clang