clang/lib/Analysis/FlowSensitive/HTMLLogger.cpp

   1 //===-- HTMLLogger.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 // This file implements the HTML logger. Given a directory dir/, we write
  10 // dir/0.html for the first analysis, etc.
  11 // These files contain a visualization that allows inspecting the CFG and the
  12 // state of the analysis at each point.
  13 // Static assets (HTMLLogger.js, HTMLLogger.css) and SVG graphs etc are embedded
  14 // so each output file is self-contained.
  15 //
  16 // VIEWS
  17 //
  18 // The timeline and function view are always shown. These allow selecting basic
  19 // blocks, statements within them, and processing iterations (BBs are visited
  20 // multiple times when e.g. loops are involved).
  21 // These are written directly into the HTML body.
  22 //
  23 // There are also listings of particular basic blocks, and dumps of the state
  24 // at particular analysis points (i.e. BB2 iteration 3 statement 2).
  25 // These are only shown when the relevant BB/analysis point is *selected*.
  26 //
  27 // DATA AND TEMPLATES
  28 //
  29 // The HTML proper is mostly static.
  30 // The analysis data is in a JSON object HTMLLoggerData which is embedded as
  31 // a <script> in the <head>.
  32 // This gets rendered into DOM by a simple template processor which substitutes
  33 // the data into <template> tags embedded in the HTML. (see inflate() in JS).
  34 //
  35 // SELECTION
  36 //
  37 // This is the only real interactive mechanism.
  38 //
  39 // At any given time, there are several named selections, e.g.:
  40 //   bb: B2               (basic block 0 is selected)
  41 //   elt: B2.4            (statement 4 is selected)
  42 //   iter: B2:1           (iteration 1 of the basic block is selected)
  43 //   hover: B3            (hovering over basic block 3)
  44 //
  45 // The selection is updated by mouse events: hover by moving the mouse and
  46 // others by clicking. Elements that are click targets generally have attributes
  47 // (id or data-foo) that define what they should select.
  48 // See watchSelection() in JS for the exact logic.
  49 //
  50 // When the "bb" selection is set to "B2":
  51 //   - sections <section data-selection="bb"> get shown
  52 //   - templates under such sections get re-rendered
  53 //   - elements with class/id "B2" get class "bb-select"
  54 //
  55 //===----------------------------------------------------------------------===//
  56
  57 #include "clang/Analysis/FlowSensitive/ControlFlowContext.h"
  58 #include "clang/Analysis/FlowSensitive/DebugSupport.h"
  59 #include "clang/Analysis/FlowSensitive/Logger.h"
  60 #include "clang/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.h"
  61 #include "clang/Analysis/FlowSensitive/Value.h"
  62 #include "clang/Basic/SourceManager.h"
  63 #include "clang/Lex/Lexer.h"
  64 #include "llvm/ADT/DenseMap.h"
  65 #include "llvm/ADT/ScopeExit.h"
  66 #include "llvm/Support/Error.h"
  67 #include "llvm/Support/FormatVariadic.h"
  68 #include "llvm/Support/JSON.h"
  69 #include "llvm/Support/Program.h"
  70 #include "llvm/Support/ScopedPrinter.h"
  71 #include "llvm/Support/raw_ostream.h"
  72 // Defines assets: HTMLLogger_{html_js,css}
  73 #include "HTMLLogger.inc"
  74
  75 namespace clang::dataflow {
  76 namespace {
  77
  78 // Render a graphviz graph specification to SVG using the `dot` tool.
  79 llvm::Expected<std::string> renderSVG(llvm::StringRef DotGraph);
  80
  81 using StreamFactory = std::function<std::unique_ptr<llvm::raw_ostream>()>;
  82
  83 // Recursively dumps Values/StorageLocations as JSON
  84 class ModelDumper {
  85 public:
  86   ModelDumper(llvm::json::OStream &JOS, const Environment &Env)
  87       : JOS(JOS), Env(Env) {}
  88
  89   void dump(Value &V) {
  90     JOS.attribute("value_id", llvm::to_string(&V));
  91     if (!Visited.insert(&V).second)
  92       return;
  93
  94     JOS.attribute("kind", debugString(V.getKind()));
  95
  96     switch (V.getKind()) {
  97     case Value::Kind::Integer:
  98     case Value::Kind::Record:
  99     case Value::Kind::TopBool:
 100     case Value::Kind::AtomicBool:
 101     case Value::Kind::FormulaBool:
 102       break;
 103     case Value::Kind::Pointer:
 104       JOS.attributeObject(
 105           "pointee", [&] { dump(cast<PointerValue>(V).getPointeeLoc()); });
 106       break;
 107     }
 108
 109     for (const auto& Prop : V.properties())
 110       JOS.attributeObject(("p:" + Prop.first()).str(),
 111                           [&] { dump(*Prop.second); });
 112
 113     // Running the SAT solver is expensive, but knowing which booleans are
 114     // guaranteed true/false here is valuable and hard to determine by hand.
 115     if (auto *B = llvm::dyn_cast<BoolValue>(&V)) {
 116       JOS.attribute("formula", llvm::to_string(B->formula()));
 117       JOS.attribute("truth", Env.proves(B->formula()) ? "true"
 118                              : Env.proves(Env.arena().makeNot(B->formula()))
 119                                  ? "false"
 120                                  : "unknown");
 121     }
 122   }
 123   void dump(const StorageLocation &L) {
 124     JOS.attribute("location", llvm::to_string(&L));
 125     if (!Visited.insert(&L).second)
 126       return;
 127
 128     JOS.attribute("type", L.getType().getAsString());
 129     if (auto *V = Env.getValue(L))
 130       dump(*V);
 131
 132     if (auto *RLoc = dyn_cast<RecordStorageLocation>(&L)) {
 133       for (const auto &Child : RLoc->children())
 134         JOS.attributeObject("f:" + Child.first->getNameAsString(), [&] {
 135           if (Child.second)
 136             if (Value *Val = Env.getValue(*Child.second))
 137               dump(*Val);
 138         });
 139     }
 140   }
 141
 142   llvm::DenseSet<const void*> Visited;
 143   llvm::json::OStream &JOS;
 144   const Environment &Env;
 145 };
 146
 147 class HTMLLogger : public Logger {
 148   struct Iteration {
 149     const CFGBlock *Block;
 150     unsigned Iter;
 151     bool PostVisit;
 152     bool Converged;
 153   };
 154
 155   StreamFactory Streams;
 156   std::unique_ptr<llvm::raw_ostream> OS;
 157   std::optional<llvm::json::OStream> JOS;
 158
 159   const ControlFlowContext *CFG;
 160   // Timeline of iterations of CFG block visitation.
 161   std::vector<Iteration> Iters;
 162   // Indexes  in `Iters` of the iterations for each block.
 163   llvm::DenseMap<const CFGBlock *, llvm::SmallVector<size_t>> BlockIters;
 164   // The messages logged in the current context but not yet written.
 165   std::string ContextLogs;
 166   // The number of elements we have visited within the current CFG block.
 167   unsigned ElementIndex;
 168
 169 public:
 170   explicit HTMLLogger(StreamFactory Streams) : Streams(std::move(Streams)) {}
 171   void beginAnalysis(const ControlFlowContext &CFG,
 172                      TypeErasedDataflowAnalysis &A) override {
 173     OS = Streams();
 174     this->CFG = &CFG;
 175     *OS << llvm::StringRef(HTMLLogger_html).split("<?INJECT?>").first;
 176
 177     const auto &D = CFG.getDecl();
 178     const auto &SM = A.getASTContext().getSourceManager();
 179     *OS << "<title>";
 180     if (const auto *ND = dyn_cast<NamedDecl>(&D))
 181       *OS << ND->getNameAsString() << " at ";
 182     *OS << SM.getFilename(D.getLocation()) << ":"
 183         << SM.getSpellingLineNumber(D.getLocation());
 184     *OS << "</title>\n";
 185
 186     *OS << "<style>" << HTMLLogger_css << "</style>\n";
 187     *OS << "<script>" << HTMLLogger_js << "</script>\n";
 188
 189     writeCode();
 190     writeCFG();
 191
 192     *OS << "<script>var HTMLLoggerData = \n";
 193     JOS.emplace(*OS, /*Indent=*/2);
 194     JOS->objectBegin();
 195     JOS->attributeBegin("states");
 196     JOS->objectBegin();
 197   }
 198   // Between beginAnalysis() and endAnalysis() we write all the states for
 199   // particular analysis points into the `timeline` array.
 200   void endAnalysis() override {
 201     JOS->objectEnd();
 202     JOS->attributeEnd();
 203
 204     JOS->attributeArray("timeline", [&] {
 205       for (const auto &E : Iters) {
 206         JOS->object([&] {
 207           JOS->attribute("block", blockID(E.Block->getBlockID()));
 208           JOS->attribute("iter", E.Iter);
 209           JOS->attribute("post_visit", E.PostVisit);
 210           JOS->attribute("converged", E.Converged);
 211         });
 212       }
 213     });
 214     JOS->attributeObject("cfg", [&] {
 215       for (const auto &E : BlockIters)
 216         writeBlock(*E.first, E.second);
 217     });
 218
 219     JOS->objectEnd();
 220     JOS.reset();
 221     *OS << ";\n</script>\n";
 222     *OS << llvm::StringRef(HTMLLogger_html).split("<?INJECT?>").second;
 223   }
 224
 225   void enterBlock(const CFGBlock &B, bool PostVisit) override {
 226     llvm::SmallVector<size_t> &BIter = BlockIters[&B];
 227     unsigned IterNum = BIter.size() + 1;
 228     BIter.push_back(Iters.size());
 229     Iters.push_back({&B, IterNum, PostVisit, /*Converged=*/false});
 230     ElementIndex = 0;
 231   }
 232   void enterElement(const CFGElement &E) override {
 233     ++ElementIndex;
 234   }
 235
 236   static std::string blockID(unsigned Block) {
 237     return llvm::formatv("B{0}", Block);
 238   }
 239   static std::string eltID(unsigned Block, unsigned Element) {
 240     return llvm::formatv("B{0}.{1}", Block, Element);
 241   }
 242   static std::string iterID(unsigned Block, unsigned Iter) {
 243     return llvm::formatv("B{0}:{1}", Block, Iter);
 244   }
 245   static std::string elementIterID(unsigned Block, unsigned Iter,
 246                                    unsigned Element) {
 247     return llvm::formatv("B{0}:{1}_B{0}.{2}", Block, Iter, Element);
 248   }
 249
 250   // Write the analysis state associated with a particular analysis point.
 251   // FIXME: this dump is fairly opaque. We should show:
 252   //  - values associated with the current Stmt
 253   //  - values associated with its children
 254   //  - meaningful names for values
 255   //  - which boolean values are implied true/false by the flow condition
 256   void recordState(TypeErasedDataflowAnalysisState &State) override {
 257     unsigned Block = Iters.back().Block->getBlockID();
 258     unsigned Iter = Iters.back().Iter;
 259     bool PostVisit = Iters.back().PostVisit;
 260     JOS->attributeObject(elementIterID(Block, Iter, ElementIndex), [&] {
 261       JOS->attribute("block", blockID(Block));
 262       JOS->attribute("iter", Iter);
 263       JOS->attribute("post_visit", PostVisit);
 264       JOS->attribute("element", ElementIndex);
 265
 266       // If this state immediately follows an Expr, show its built-in model.
 267       if (ElementIndex > 0) {
 268         auto S =
 269             Iters.back().Block->Elements[ElementIndex - 1].getAs<CFGStmt>();
 270         if (const Expr *E = S ? llvm::dyn_cast<Expr>(S->getStmt()) : nullptr) {
 271           if (E->isPRValue()) {
 272             if (auto *V = State.Env.getValue(*E))
 273               JOS->attributeObject(
 274                   "value", [&] { ModelDumper(*JOS, State.Env).dump(*V); });
 275           } else {
 276             if (auto *Loc = State.Env.getStorageLocation(*E))
 277               JOS->attributeObject(
 278                   "value", [&] { ModelDumper(*JOS, State.Env).dump(*Loc); });
 279           }
 280         }
 281       }
 282       if (!ContextLogs.empty()) {
 283         JOS->attribute("logs", ContextLogs);
 284         ContextLogs.clear();
 285       }
 286       {
 287         std::string BuiltinLattice;
 288         llvm::raw_string_ostream BuiltinLatticeS(BuiltinLattice);
 289         State.Env.dump(BuiltinLatticeS);
 290         JOS->attribute("builtinLattice", BuiltinLattice);
 291       }
 292     });
 293   }
 294   void blockConverged() override { Iters.back().Converged = true; }
 295
 296   void logText(llvm::StringRef S) override {
 297     ContextLogs.append(S.begin(), S.end());
 298     ContextLogs.push_back('\n');
 299   }
 300
 301 private:
 302   // Write the CFG block details.
 303   // Currently this is just the list of elements in execution order.
 304   // FIXME: an AST dump would be a useful view, too.
 305   void writeBlock(const CFGBlock &B, llvm::ArrayRef<size_t> ItersForB) {
 306     JOS->attributeObject(blockID(B.getBlockID()), [&] {
 307       JOS->attributeArray("iters", [&] {
 308         for (size_t IterIdx : ItersForB) {
 309           const Iteration &Iter = Iters[IterIdx];
 310           JOS->object([&] {
 311             JOS->attribute("iter", Iter.Iter);
 312             JOS->attribute("post_visit", Iter.PostVisit);
 313             JOS->attribute("converged", Iter.Converged);
 314           });
 315         }
 316       });
 317       JOS->attributeArray("elements", [&] {
 318         for (const auto &Elt : B.Elements) {
 319           std::string Dump;
 320           llvm::raw_string_ostream DumpS(Dump);
 321           Elt.dumpToStream(DumpS);
 322           JOS->value(Dump);
 323         }
 324       });
 325     });
 326   }
 327
 328   // Write the code of function being examined.
 329   // We want to overlay the code with <span>s that mark which BB particular
 330   // tokens are associated with, and even which BB element (so that clicking
 331   // can select the right element).
 332   void writeCode() {
 333     const auto &AST = CFG->getDecl().getASTContext();
 334     bool Invalid = false;
 335
 336     // Extract the source code from the original file.
 337     // Pretty-printing from the AST would probably be nicer (no macros or
 338     // indentation to worry about), but we need the boundaries of particular
 339     // AST nodes and the printer doesn't provide this.
 340     auto Range = clang::Lexer::makeFileCharRange(
 341         CharSourceRange::getTokenRange(CFG->getDecl().getSourceRange()),
 342         AST.getSourceManager(), AST.getLangOpts());
 343     if (Range.isInvalid())
 344       return;
 345     llvm::StringRef Code = clang::Lexer::getSourceText(
 346         Range, AST.getSourceManager(), AST.getLangOpts(), &Invalid);
 347     if (Invalid)
 348       return;
 349
 350     static constexpr unsigned Missing = -1;
 351     // TokenInfo stores the BB and set of elements that a token is part of.
 352     struct TokenInfo {
 353       // The basic block this is part of.
 354       // This is the BB of the stmt with the smallest containing range.
 355       unsigned BB = Missing;
 356       unsigned BBPriority = 0;
 357       // The most specific stmt this is part of (smallest range).
 358       unsigned Elt = Missing;
 359       unsigned EltPriority = 0;
 360       // All stmts this is part of.
 361       SmallVector<unsigned> Elts;
 362
 363       // Mark this token as being part of BB.Elt.
 364       // RangeLen is the character length of the element's range, used to
 365       // distinguish inner vs outer statements.
 366       // For example in `a==0`, token "a" is part of the stmts "a" and "a==0".
 367       // However "a" has a smaller range, so is more specific. Clicking on the
 368       // token "a" should select the stmt "a".
 369       void assign(unsigned BB, unsigned Elt, unsigned RangeLen) {
 370         // A worse BB (larger range) => ignore.
 371         if (this->BB != Missing && BB != this->BB && BBPriority <= RangeLen)
 372           return;
 373         if (BB != this->BB) {
 374           this->BB = BB;
 375           Elts.clear();
 376           BBPriority = RangeLen;
 377         }
 378         BBPriority = std::min(BBPriority, RangeLen);
 379         Elts.push_back(Elt);
 380         if (this->Elt == Missing || EltPriority > RangeLen)
 381           this->Elt = Elt;
 382       }
 383       bool operator==(const TokenInfo &Other) const {
 384         return std::tie(BB, Elt, Elts) ==
 385                std::tie(Other.BB, Other.Elt, Other.Elts);
 386       }
 387       // Write the attributes for the <span> on this token.
 388       void write(llvm::raw_ostream &OS) const {
 389         OS << "class='c";
 390         if (BB != Missing)
 391           OS << " " << blockID(BB);
 392         for (unsigned Elt : Elts)
 393           OS << " " << eltID(BB, Elt);
 394         OS << "'";
 395
 396         if (Elt != Missing)
 397           OS << " data-elt='" << eltID(BB, Elt) << "'";
 398         if (BB != Missing)
 399           OS << " data-bb='" << blockID(BB) << "'";
 400       }
 401     };
 402
 403     // Construct one TokenInfo per character in a flat array.
 404     // This is inefficient (chars in a token all have the same info) but simple.
 405     std::vector<TokenInfo> State(Code.size());
 406     for (const auto *Block : CFG->getCFG()) {
 407       unsigned EltIndex = 0;
 408       for (const auto& Elt : *Block) {
 409         ++EltIndex;
 410         if (const auto S = Elt.getAs<CFGStmt>()) {
 411           auto EltRange = clang::Lexer::makeFileCharRange(
 412               CharSourceRange::getTokenRange(S->getStmt()->getSourceRange()),
 413               AST.getSourceManager(), AST.getLangOpts());
 414           if (EltRange.isInvalid())
 415             continue;
 416           if (EltRange.getBegin() < Range.getBegin() ||
 417               EltRange.getEnd() >= Range.getEnd() ||
 418               EltRange.getEnd() < Range.getBegin() ||
 419               EltRange.getEnd() >= Range.getEnd())
 420             continue;
 421           unsigned Off = EltRange.getBegin().getRawEncoding() -
 422                          Range.getBegin().getRawEncoding();
 423           unsigned Len = EltRange.getEnd().getRawEncoding() -
 424                          EltRange.getBegin().getRawEncoding();
 425           for (unsigned I = 0; I < Len; ++I)
 426             State[Off + I].assign(Block->getBlockID(), EltIndex, Len);
 427         }
 428       }
 429     }
 430
 431     // Finally, write the code with the correct <span>s.
 432     unsigned Line =
 433         AST.getSourceManager().getSpellingLineNumber(Range.getBegin());
 434     *OS << "<template data-copy='code'>\n";
 435     *OS << "<code class='filename'>";
 436     llvm::printHTMLEscaped(
 437         llvm::sys::path::filename(
 438             AST.getSourceManager().getFilename(Range.getBegin())),
 439         *OS);
 440     *OS << "</code>";
 441     *OS << "<code class='line' data-line='" << Line++ << "'>";
 442     for (unsigned I = 0; I < Code.size(); ++I) {
 443       // Don't actually write a <span> around each character, only break spans
 444       // when the TokenInfo changes.
 445       bool NeedOpen = I == 0 || !(State[I] == State[I-1]);
 446       bool NeedClose = I + 1 == Code.size() || !(State[I] == State[I + 1]);
 447       if (NeedOpen) {
 448         *OS << "<span ";
 449         State[I].write(*OS);
 450         *OS << ">";
 451       }
 452       if (Code[I] == '\n')
 453         *OS << "</code>\n<code class='line' data-line='" << Line++ << "'>";
 454       else
 455         llvm::printHTMLEscaped(Code.substr(I, 1), *OS);
 456       if (NeedClose) *OS << "</span>";
 457     }
 458     *OS << "</code>\n";
 459     *OS << "</template>";
 460   }
 461
 462   // Write the CFG diagram, a graph of basic blocks.
 463   // Laying out graphs is hard, so we construct a graphviz description and shell
 464   // out to `dot` to turn it into an SVG.
 465   void writeCFG() {
 466     *OS << "<template data-copy='cfg'>\n";
 467     if (auto SVG = renderSVG(buildCFGDot(CFG->getCFG())))
 468       *OS << *SVG;
 469     else
 470       *OS << "Can't draw CFG: " << toString(SVG.takeError());
 471     *OS << "</template>\n";
 472   }
 473
 474   // Produce a graphviz description of a CFG.
 475   static std::string buildCFGDot(const clang::CFG &CFG) {
 476     std::string Graph;
 477     llvm::raw_string_ostream GraphS(Graph);
 478     // Graphviz likes to add unhelpful tooltips everywhere, " " suppresses.
 479     GraphS << R"(digraph {
 480       tooltip=" "
 481       node[class=bb, shape=square, fontname="sans-serif", tooltip=" "]
 482       edge[tooltip = " "]
 483 )";
 484     for (unsigned I = 0; I < CFG.getNumBlockIDs(); ++I)
 485       GraphS << "  " << blockID(I) << " [id=" << blockID(I) << "]\n";
 486     for (const auto *Block : CFG) {
 487       for (const auto &Succ : Block->succs()) {
 488         if (Succ.getReachableBlock())
 489           GraphS << "  " << blockID(Block->getBlockID()) << " -> "
 490                  << blockID(Succ.getReachableBlock()->getBlockID()) << "\n";
 491       }
 492     }
 493     GraphS << "}\n";
 494     return Graph;
 495   }
 496 };
 497
 498 // Nothing interesting here, just subprocess/temp-file plumbing.
 499 llvm::Expected<std::string> renderSVG(llvm::StringRef DotGraph) {
 500   std::string DotPath;
 501   if (const auto *FromEnv = ::getenv("GRAPHVIZ_DOT"))
 502     DotPath = FromEnv;
 503   else {
 504     auto FromPath = llvm::sys::findProgramByName("dot");
 505     if (!FromPath)
 506       return llvm::createStringError(FromPath.getError(),
 507                                      "'dot' not found on PATH");
 508     DotPath = FromPath.get();
 509   }
 510
 511   // Create input and output files for `dot` subprocess.
 512   // (We create the output file as empty, to reserve the temp filename).
 513   llvm::SmallString<256> Input, Output;
 514   int InputFD;
 515   if (auto EC = llvm::sys::fs::createTemporaryFile("analysis", ".dot", InputFD,
 516                                                    Input))
 517     return llvm::createStringError(EC, "failed to create `dot` temp input");
 518   llvm::raw_fd_ostream(InputFD, /*shouldClose=*/true) << DotGraph;
 519   auto DeleteInput =
 520       llvm::make_scope_exit([&] { llvm::sys::fs::remove(Input); });
 521   if (auto EC = llvm::sys::fs::createTemporaryFile("analysis", ".svg", Output))
 522     return llvm::createStringError(EC, "failed to create `dot` temp output");
 523   auto DeleteOutput =
 524       llvm::make_scope_exit([&] { llvm::sys::fs::remove(Output); });
 525
 526   std::vector<std::optional<llvm::StringRef>> Redirects = {
 527       Input, Output,
 528       /*stderr=*/std::nullopt};
 529   std::string ErrMsg;
 530   int Code = llvm::sys::ExecuteAndWait(
 531       DotPath, {"dot", "-Tsvg"}, /*Env=*/std::nullopt, Redirects,
 532       /*SecondsToWait=*/0, /*MemoryLimit=*/0, &ErrMsg);
 533   if (!ErrMsg.empty())
 534     return llvm::createStringError(llvm::inconvertibleErrorCode(),
 535                                    "'dot' failed: " + ErrMsg);
 536   if (Code != 0)
 537     return llvm::createStringError(llvm::inconvertibleErrorCode(),
 538                                    "'dot' failed (" + llvm::Twine(Code) + ")");
 539
 540   auto Buf = llvm::MemoryBuffer::getFile(Output);
 541   if (!Buf)
 542     return llvm::createStringError(Buf.getError(), "Can't read `dot` output");
 543
 544   // Output has <?xml> prefix we don't want. Skip to <svg> tag.
 545   llvm::StringRef Result = Buf.get()->getBuffer();
 546   auto Pos = Result.find("<svg");
 547   if (Pos == llvm::StringRef::npos)
 548     return llvm::createStringError(llvm::inconvertibleErrorCode(),
 549                                    "Can't find <svg> tag in `dot` output");
 550   return Result.substr(Pos).str();
 551 }
 552
 553 } // namespace
 554
 555 std::unique_ptr<Logger>
 556 Logger::html(std::function<std::unique_ptr<llvm::raw_ostream>()> Streams) {
 557   return std::make_unique<HTMLLogger>(std::move(Streams));
 558 }
 559
 560 } // namespace clang::dataflow