xref: /llvm-project/clang/lib/Frontend/DiagnosticRenderer.cpp (revision 4dd55c567aaed30c6842812e0798a70fee324c98)
1 //===- DiagnosticRenderer.cpp - Diagnostic Pretty-Printing ----------------===//
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 "clang/Frontend/DiagnosticRenderer.h"
10 #include "clang/Basic/Diagnostic.h"
11 #include "clang/Basic/DiagnosticOptions.h"
12 #include "clang/Basic/LLVM.h"
13 #include "clang/Basic/SourceLocation.h"
14 #include "clang/Basic/SourceManager.h"
15 #include "clang/Edit/Commit.h"
16 #include "clang/Edit/EditedSource.h"
17 #include "clang/Edit/EditsReceiver.h"
18 #include "clang/Lex/Lexer.h"
19 #include "llvm/ADT/ArrayRef.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/ADT/StringRef.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include <algorithm>
26 #include <cassert>
27 #include <iterator>
28 #include <utility>
29 
30 using namespace clang;
31 
32 DiagnosticRenderer::DiagnosticRenderer(const LangOptions &LangOpts,
33                                        DiagnosticOptions *DiagOpts)
34     : LangOpts(LangOpts), DiagOpts(DiagOpts), LastLevel() {}
35 
36 DiagnosticRenderer::~DiagnosticRenderer() = default;
37 
38 namespace {
39 
40 class FixitReceiver : public edit::EditsReceiver {
41   SmallVectorImpl<FixItHint> &MergedFixits;
42 
43 public:
44   FixitReceiver(SmallVectorImpl<FixItHint> &MergedFixits)
45       : MergedFixits(MergedFixits) {}
46 
47   void insert(SourceLocation loc, StringRef text) override {
48     MergedFixits.push_back(FixItHint::CreateInsertion(loc, text));
49   }
50 
51   void replace(CharSourceRange range, StringRef text) override {
52     MergedFixits.push_back(FixItHint::CreateReplacement(range, text));
53   }
54 };
55 
56 } // namespace
57 
58 static void mergeFixits(ArrayRef<FixItHint> FixItHints,
59                         const SourceManager &SM, const LangOptions &LangOpts,
60                         SmallVectorImpl<FixItHint> &MergedFixits) {
61   edit::Commit commit(SM, LangOpts);
62   for (const auto &Hint : FixItHints)
63     if (Hint.CodeToInsert.empty()) {
64       if (Hint.InsertFromRange.isValid())
65         commit.insertFromRange(Hint.RemoveRange.getBegin(),
66                            Hint.InsertFromRange, /*afterToken=*/false,
67                            Hint.BeforePreviousInsertions);
68       else
69         commit.remove(Hint.RemoveRange);
70     } else {
71       if (Hint.RemoveRange.isTokenRange() ||
72           Hint.RemoveRange.getBegin() != Hint.RemoveRange.getEnd())
73         commit.replace(Hint.RemoveRange, Hint.CodeToInsert);
74       else
75         commit.insert(Hint.RemoveRange.getBegin(), Hint.CodeToInsert,
76                     /*afterToken=*/false, Hint.BeforePreviousInsertions);
77     }
78 
79   edit::EditedSource Editor(SM, LangOpts);
80   if (Editor.commit(commit)) {
81     FixitReceiver Rec(MergedFixits);
82     Editor.applyRewrites(Rec);
83   }
84 }
85 
86 void DiagnosticRenderer::emitDiagnostic(FullSourceLoc Loc,
87                                         DiagnosticsEngine::Level Level,
88                                         StringRef Message,
89                                         ArrayRef<CharSourceRange> Ranges,
90                                         ArrayRef<FixItHint> FixItHints,
91                                         DiagOrStoredDiag D) {
92   assert(Loc.hasManager() || Loc.isInvalid());
93 
94   beginDiagnostic(D, Level);
95 
96   if (!Loc.isValid())
97     // If we have no source location, just emit the diagnostic message.
98     emitDiagnosticMessage(Loc, PresumedLoc(), Level, Message, Ranges, D);
99   else {
100     // Get the ranges into a local array we can hack on.
101     SmallVector<CharSourceRange, 20> MutableRanges(Ranges);
102 
103     SmallVector<FixItHint, 8> MergedFixits;
104     if (!FixItHints.empty()) {
105       mergeFixits(FixItHints, Loc.getManager(), LangOpts, MergedFixits);
106       FixItHints = MergedFixits;
107     }
108 
109     for (const auto &Hint : FixItHints)
110       if (Hint.RemoveRange.isValid())
111         MutableRanges.push_back(Hint.RemoveRange);
112 
113     FullSourceLoc UnexpandedLoc = Loc;
114 
115     // Find the ultimate expansion location for the diagnostic.
116     Loc = Loc.getFileLoc();
117 
118     PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
119 
120     // First, if this diagnostic is not in the main file, print out the
121     // "included from" lines.
122     emitIncludeStack(Loc, PLoc, Level);
123 
124     // Next, emit the actual diagnostic message and caret.
125     emitDiagnosticMessage(Loc, PLoc, Level, Message, Ranges, D);
126     emitCaret(Loc, Level, MutableRanges, FixItHints);
127 
128     // If this location is within a macro, walk from UnexpandedLoc up to Loc
129     // and produce a macro backtrace.
130     if (UnexpandedLoc.isValid() && UnexpandedLoc.isMacroID()) {
131       emitMacroExpansions(UnexpandedLoc, Level, MutableRanges, FixItHints);
132     }
133   }
134 
135   LastLoc = Loc;
136   LastLevel = Level;
137 
138   endDiagnostic(D, Level);
139 }
140 
141 void DiagnosticRenderer::emitStoredDiagnostic(StoredDiagnostic &Diag) {
142   emitDiagnostic(Diag.getLocation(), Diag.getLevel(), Diag.getMessage(),
143                  Diag.getRanges(), Diag.getFixIts(),
144                  &Diag);
145 }
146 
147 void DiagnosticRenderer::emitBasicNote(StringRef Message) {
148   emitDiagnosticMessage(FullSourceLoc(), PresumedLoc(), DiagnosticsEngine::Note,
149                         Message, {}, DiagOrStoredDiag());
150 }
151 
152 /// Prints an include stack when appropriate for a particular
153 /// diagnostic level and location.
154 ///
155 /// This routine handles all the logic of suppressing particular include
156 /// stacks (such as those for notes) and duplicate include stacks when
157 /// repeated warnings occur within the same file. It also handles the logic
158 /// of customizing the formatting and display of the include stack.
159 ///
160 /// \param Loc   The diagnostic location.
161 /// \param PLoc  The presumed location of the diagnostic location.
162 /// \param Level The diagnostic level of the message this stack pertains to.
163 void DiagnosticRenderer::emitIncludeStack(FullSourceLoc Loc, PresumedLoc PLoc,
164                                           DiagnosticsEngine::Level Level) {
165   FullSourceLoc IncludeLoc =
166       PLoc.isInvalid() ? FullSourceLoc()
167                        : FullSourceLoc(PLoc.getIncludeLoc(), Loc.getManager());
168 
169   // Skip redundant include stacks altogether.
170   if (LastIncludeLoc == IncludeLoc)
171     return;
172 
173   LastIncludeLoc = IncludeLoc;
174 
175   if (!DiagOpts->ShowNoteIncludeStack && Level == DiagnosticsEngine::Note)
176     return;
177 
178   if (IncludeLoc.isValid())
179     emitIncludeStackRecursively(IncludeLoc);
180   else {
181     emitModuleBuildStack(Loc.getManager());
182     emitImportStack(Loc);
183   }
184 }
185 
186 /// Helper to recursively walk up the include stack and print each layer
187 /// on the way back down.
188 void DiagnosticRenderer::emitIncludeStackRecursively(FullSourceLoc Loc) {
189   if (Loc.isInvalid()) {
190     emitModuleBuildStack(Loc.getManager());
191     return;
192   }
193 
194   PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
195   if (PLoc.isInvalid())
196     return;
197 
198   // If this source location was imported from a module, print the module
199   // import stack rather than the
200   // FIXME: We want submodule granularity here.
201   std::pair<FullSourceLoc, StringRef> Imported = Loc.getModuleImportLoc();
202   if (!Imported.second.empty()) {
203     // This location was imported by a module. Emit the module import stack.
204     emitImportStackRecursively(Imported.first, Imported.second);
205     return;
206   }
207 
208   // Emit the other include frames first.
209   emitIncludeStackRecursively(
210       FullSourceLoc(PLoc.getIncludeLoc(), Loc.getManager()));
211 
212   // Emit the inclusion text/note.
213   emitIncludeLocation(Loc, PLoc);
214 }
215 
216 /// Emit the module import stack associated with the current location.
217 void DiagnosticRenderer::emitImportStack(FullSourceLoc Loc) {
218   if (Loc.isInvalid()) {
219     emitModuleBuildStack(Loc.getManager());
220     return;
221   }
222 
223   std::pair<FullSourceLoc, StringRef> NextImportLoc = Loc.getModuleImportLoc();
224   emitImportStackRecursively(NextImportLoc.first, NextImportLoc.second);
225 }
226 
227 /// Helper to recursively walk up the import stack and print each layer
228 /// on the way back down.
229 void DiagnosticRenderer::emitImportStackRecursively(FullSourceLoc Loc,
230                                                     StringRef ModuleName) {
231   if (ModuleName.empty()) {
232     return;
233   }
234 
235   PresumedLoc PLoc = Loc.getPresumedLoc(DiagOpts->ShowPresumedLoc);
236 
237   // Emit the other import frames first.
238   std::pair<FullSourceLoc, StringRef> NextImportLoc = Loc.getModuleImportLoc();
239   emitImportStackRecursively(NextImportLoc.first, NextImportLoc.second);
240 
241   // Emit the inclusion text/note.
242   emitImportLocation(Loc, PLoc, ModuleName);
243 }
244 
245 /// Emit the module build stack, for cases where a module is (re-)built
246 /// on demand.
247 void DiagnosticRenderer::emitModuleBuildStack(const SourceManager &SM) {
248   ModuleBuildStack Stack = SM.getModuleBuildStack();
249   for (const auto &I : Stack) {
250     emitBuildingModuleLocation(I.second, I.second.getPresumedLoc(
251                                               DiagOpts->ShowPresumedLoc),
252                                I.first);
253   }
254 }
255 
256 /// A recursive function to trace all possible backtrace locations
257 /// to match the \p CaretLocFileID.
258 static SourceLocation
259 retrieveMacroLocation(SourceLocation Loc, FileID MacroFileID,
260                       FileID CaretFileID,
261                       const SmallVectorImpl<FileID> &CommonArgExpansions,
262                       bool IsBegin, const SourceManager *SM,
263                       bool &IsTokenRange) {
264   assert(SM->getFileID(Loc) == MacroFileID);
265   if (MacroFileID == CaretFileID)
266     return Loc;
267   if (!Loc.isMacroID())
268     return {};
269 
270   CharSourceRange MacroRange, MacroArgRange;
271 
272   if (SM->isMacroArgExpansion(Loc)) {
273     // Only look at the immediate spelling location of this macro argument if
274     // the other location in the source range is also present in that expansion.
275     if (std::binary_search(CommonArgExpansions.begin(),
276                            CommonArgExpansions.end(), MacroFileID))
277       MacroRange =
278           CharSourceRange(SM->getImmediateSpellingLoc(Loc), IsTokenRange);
279     MacroArgRange = SM->getImmediateExpansionRange(Loc);
280   } else {
281     MacroRange = SM->getImmediateExpansionRange(Loc);
282     MacroArgRange =
283         CharSourceRange(SM->getImmediateSpellingLoc(Loc), IsTokenRange);
284   }
285 
286   SourceLocation MacroLocation =
287       IsBegin ? MacroRange.getBegin() : MacroRange.getEnd();
288   if (MacroLocation.isValid()) {
289     MacroFileID = SM->getFileID(MacroLocation);
290     bool TokenRange = IsBegin ? IsTokenRange : MacroRange.isTokenRange();
291     MacroLocation =
292         retrieveMacroLocation(MacroLocation, MacroFileID, CaretFileID,
293                               CommonArgExpansions, IsBegin, SM, TokenRange);
294     if (MacroLocation.isValid()) {
295       IsTokenRange = TokenRange;
296       return MacroLocation;
297     }
298   }
299 
300   // If we moved the end of the range to an expansion location, we now have
301   // a range of the same kind as the expansion range.
302   if (!IsBegin)
303     IsTokenRange = MacroArgRange.isTokenRange();
304 
305   SourceLocation MacroArgLocation =
306       IsBegin ? MacroArgRange.getBegin() : MacroArgRange.getEnd();
307   MacroFileID = SM->getFileID(MacroArgLocation);
308   return retrieveMacroLocation(MacroArgLocation, MacroFileID, CaretFileID,
309                                CommonArgExpansions, IsBegin, SM, IsTokenRange);
310 }
311 
312 /// Walk up the chain of macro expansions and collect the FileIDs identifying the
313 /// expansions.
314 static void getMacroArgExpansionFileIDs(SourceLocation Loc,
315                                         SmallVectorImpl<FileID> &IDs,
316                                         bool IsBegin, const SourceManager *SM) {
317   while (Loc.isMacroID()) {
318     if (SM->isMacroArgExpansion(Loc)) {
319       IDs.push_back(SM->getFileID(Loc));
320       Loc = SM->getImmediateSpellingLoc(Loc);
321     } else {
322       auto ExpRange = SM->getImmediateExpansionRange(Loc);
323       Loc = IsBegin ? ExpRange.getBegin() : ExpRange.getEnd();
324     }
325   }
326 }
327 
328 /// Collect the expansions of the begin and end locations and compute the set
329 /// intersection. Produces a sorted vector of FileIDs in CommonArgExpansions.
330 static void computeCommonMacroArgExpansionFileIDs(
331     SourceLocation Begin, SourceLocation End, const SourceManager *SM,
332     SmallVectorImpl<FileID> &CommonArgExpansions) {
333   SmallVector<FileID, 4> BeginArgExpansions;
334   SmallVector<FileID, 4> EndArgExpansions;
335   getMacroArgExpansionFileIDs(Begin, BeginArgExpansions, /*IsBegin=*/true, SM);
336   getMacroArgExpansionFileIDs(End, EndArgExpansions, /*IsBegin=*/false, SM);
337   llvm::sort(BeginArgExpansions);
338   llvm::sort(EndArgExpansions);
339   std::set_intersection(BeginArgExpansions.begin(), BeginArgExpansions.end(),
340                         EndArgExpansions.begin(), EndArgExpansions.end(),
341                         std::back_inserter(CommonArgExpansions));
342 }
343 
344 // Helper function to fix up source ranges.  It takes in an array of ranges,
345 // and outputs an array of ranges where we want to draw the range highlighting
346 // around the location specified by CaretLoc.
347 //
348 // To find locations which correspond to the caret, we crawl the macro caller
349 // chain for the beginning and end of each range.  If the caret location
350 // is in a macro expansion, we search each chain for a location
351 // in the same expansion as the caret; otherwise, we crawl to the top of
352 // each chain. Two locations are part of the same macro expansion
353 // iff the FileID is the same.
354 static void
355 mapDiagnosticRanges(FullSourceLoc CaretLoc, ArrayRef<CharSourceRange> Ranges,
356                     SmallVectorImpl<CharSourceRange> &SpellingRanges) {
357   FileID CaretLocFileID = CaretLoc.getFileID();
358 
359   const SourceManager *SM = &CaretLoc.getManager();
360 
361   for (const auto &Range : Ranges) {
362     if (Range.isInvalid())
363       continue;
364 
365     SourceLocation Begin = Range.getBegin(), End = Range.getEnd();
366     bool IsTokenRange = Range.isTokenRange();
367 
368     FileID BeginFileID = SM->getFileID(Begin);
369     FileID EndFileID = SM->getFileID(End);
370 
371     // Find the common parent for the beginning and end of the range.
372 
373     // First, crawl the expansion chain for the beginning of the range.
374     llvm::SmallDenseMap<FileID, SourceLocation> BeginLocsMap;
375     while (Begin.isMacroID() && BeginFileID != EndFileID) {
376       BeginLocsMap[BeginFileID] = Begin;
377       Begin = SM->getImmediateExpansionRange(Begin).getBegin();
378       BeginFileID = SM->getFileID(Begin);
379     }
380 
381     // Then, crawl the expansion chain for the end of the range.
382     if (BeginFileID != EndFileID) {
383       while (End.isMacroID() && !BeginLocsMap.count(EndFileID)) {
384         auto Exp = SM->getImmediateExpansionRange(End);
385         IsTokenRange = Exp.isTokenRange();
386         End = Exp.getEnd();
387         EndFileID = SM->getFileID(End);
388       }
389       if (End.isMacroID()) {
390         Begin = BeginLocsMap[EndFileID];
391         BeginFileID = EndFileID;
392       }
393     }
394 
395     // There is a chance that begin or end is invalid here, for example if
396     // specific compile error is reported.
397     // It is possible that the FileID's do not match, if one comes from an
398     // included file. In this case we can not produce a meaningful source range.
399     if (Begin.isInvalid() || End.isInvalid() || BeginFileID != EndFileID)
400       continue;
401 
402     // Do the backtracking.
403     SmallVector<FileID, 4> CommonArgExpansions;
404     computeCommonMacroArgExpansionFileIDs(Begin, End, SM, CommonArgExpansions);
405     Begin = retrieveMacroLocation(Begin, BeginFileID, CaretLocFileID,
406                                   CommonArgExpansions, /*IsBegin=*/true, SM,
407                                   IsTokenRange);
408     End = retrieveMacroLocation(End, BeginFileID, CaretLocFileID,
409                                 CommonArgExpansions, /*IsBegin=*/false, SM,
410                                 IsTokenRange);
411     if (Begin.isInvalid() || End.isInvalid()) continue;
412 
413     // Return the spelling location of the beginning and end of the range.
414     Begin = SM->getSpellingLoc(Begin);
415     End = SM->getSpellingLoc(End);
416 
417     SpellingRanges.push_back(CharSourceRange(SourceRange(Begin, End),
418                                              IsTokenRange));
419   }
420 }
421 
422 void DiagnosticRenderer::emitCaret(FullSourceLoc Loc,
423                                    DiagnosticsEngine::Level Level,
424                                    ArrayRef<CharSourceRange> Ranges,
425                                    ArrayRef<FixItHint> Hints) {
426   SmallVector<CharSourceRange, 4> SpellingRanges;
427   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
428   emitCodeContext(Loc, Level, SpellingRanges, Hints);
429 }
430 
431 /// A helper function for emitMacroExpansion to print the
432 /// macro expansion message
433 void DiagnosticRenderer::emitSingleMacroExpansion(
434     FullSourceLoc Loc, DiagnosticsEngine::Level Level,
435     ArrayRef<CharSourceRange> Ranges) {
436   // Find the spelling location for the macro definition. We must use the
437   // spelling location here to avoid emitting a macro backtrace for the note.
438   FullSourceLoc SpellingLoc = Loc.getSpellingLoc();
439 
440   // Map the ranges into the FileID of the diagnostic location.
441   SmallVector<CharSourceRange, 4> SpellingRanges;
442   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
443 
444   SmallString<100> MessageStorage;
445   llvm::raw_svector_ostream Message(MessageStorage);
446   StringRef MacroName = Lexer::getImmediateMacroNameForDiagnostics(
447       Loc, Loc.getManager(), LangOpts);
448   if (MacroName.empty())
449     Message << "expanded from here";
450   else
451     Message << "expanded from macro '" << MacroName << "'";
452 
453   emitDiagnostic(SpellingLoc, DiagnosticsEngine::Note, Message.str(),
454                  SpellingRanges, {});
455 }
456 
457 /// Check that the macro argument location of Loc starts with ArgumentLoc.
458 /// The starting location of the macro expansions is used to differeniate
459 /// different macro expansions.
460 static bool checkLocForMacroArgExpansion(SourceLocation Loc,
461                                          const SourceManager &SM,
462                                          SourceLocation ArgumentLoc) {
463   SourceLocation MacroLoc;
464   if (SM.isMacroArgExpansion(Loc, &MacroLoc)) {
465     if (ArgumentLoc == MacroLoc) return true;
466   }
467 
468   return false;
469 }
470 
471 /// Check if all the locations in the range have the same macro argument
472 /// expansion, and that the expansion starts with ArgumentLoc.
473 static bool checkRangeForMacroArgExpansion(CharSourceRange Range,
474                                            const SourceManager &SM,
475                                            SourceLocation ArgumentLoc) {
476   SourceLocation BegLoc = Range.getBegin(), EndLoc = Range.getEnd();
477   while (BegLoc != EndLoc) {
478     if (!checkLocForMacroArgExpansion(BegLoc, SM, ArgumentLoc))
479       return false;
480     BegLoc.getLocWithOffset(1);
481   }
482 
483   return checkLocForMacroArgExpansion(BegLoc, SM, ArgumentLoc);
484 }
485 
486 /// A helper function to check if the current ranges are all inside the same
487 /// macro argument expansion as Loc.
488 static bool checkRangesForMacroArgExpansion(FullSourceLoc Loc,
489                                             ArrayRef<CharSourceRange> Ranges) {
490   assert(Loc.isMacroID() && "Must be a macro expansion!");
491 
492   SmallVector<CharSourceRange, 4> SpellingRanges;
493   mapDiagnosticRanges(Loc, Ranges, SpellingRanges);
494 
495   // Count all valid ranges.
496   unsigned ValidCount =
497       llvm::count_if(Ranges, [](const auto &R) { return R.isValid(); });
498 
499   if (ValidCount > SpellingRanges.size())
500     return false;
501 
502   // To store the source location of the argument location.
503   FullSourceLoc ArgumentLoc;
504 
505   // Set the ArgumentLoc to the beginning location of the expansion of Loc
506   // so to check if the ranges expands to the same beginning location.
507   if (!Loc.isMacroArgExpansion(&ArgumentLoc))
508     return false;
509 
510   for (const auto &Range : SpellingRanges)
511     if (!checkRangeForMacroArgExpansion(Range, Loc.getManager(), ArgumentLoc))
512       return false;
513 
514   return true;
515 }
516 
517 /// Recursively emit notes for each macro expansion and caret
518 /// diagnostics where appropriate.
519 ///
520 /// Walks up the macro expansion stack printing expansion notes, the code
521 /// snippet, caret, underlines and FixItHint display as appropriate at each
522 /// level.
523 ///
524 /// \param Loc The location for this caret.
525 /// \param Level The diagnostic level currently being emitted.
526 /// \param Ranges The underlined ranges for this code snippet.
527 /// \param Hints The FixIt hints active for this diagnostic.
528 void DiagnosticRenderer::emitMacroExpansions(FullSourceLoc Loc,
529                                              DiagnosticsEngine::Level Level,
530                                              ArrayRef<CharSourceRange> Ranges,
531                                              ArrayRef<FixItHint> Hints) {
532   assert(Loc.isValid() && "must have a valid source location here");
533   const SourceManager &SM = Loc.getManager();
534   SourceLocation L = Loc;
535 
536   // Produce a stack of macro backtraces.
537   SmallVector<SourceLocation, 8> LocationStack;
538   unsigned IgnoredEnd = 0;
539   while (L.isMacroID()) {
540     // If this is the expansion of a macro argument, point the caret at the
541     // use of the argument in the definition of the macro, not the expansion.
542     if (SM.isMacroArgExpansion(L))
543       LocationStack.push_back(SM.getImmediateExpansionRange(L).getBegin());
544     else
545       LocationStack.push_back(L);
546 
547     if (checkRangesForMacroArgExpansion(FullSourceLoc(L, SM), Ranges))
548       IgnoredEnd = LocationStack.size();
549 
550     L = SM.getImmediateMacroCallerLoc(L);
551 
552     // Once the location no longer points into a macro, try stepping through
553     // the last found location.  This sometimes produces additional useful
554     // backtraces.
555     if (L.isFileID())
556       L = SM.getImmediateMacroCallerLoc(LocationStack.back());
557     assert(L.isValid() && "must have a valid source location here");
558   }
559 
560   LocationStack.erase(LocationStack.begin(),
561                       LocationStack.begin() + IgnoredEnd);
562 
563   unsigned MacroDepth = LocationStack.size();
564   unsigned MacroLimit = DiagOpts->MacroBacktraceLimit;
565   if (MacroDepth <= MacroLimit || MacroLimit == 0) {
566     for (auto I = LocationStack.rbegin(), E = LocationStack.rend();
567          I != E; ++I)
568       emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
569     return;
570   }
571 
572   unsigned MacroStartMessages = MacroLimit / 2;
573   unsigned MacroEndMessages = MacroLimit / 2 + MacroLimit % 2;
574 
575   for (auto I = LocationStack.rbegin(),
576             E = LocationStack.rbegin() + MacroStartMessages;
577        I != E; ++I)
578     emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
579 
580   SmallString<200> MessageStorage;
581   llvm::raw_svector_ostream Message(MessageStorage);
582   Message << "(skipping " << (MacroDepth - MacroLimit)
583           << " expansions in backtrace; use -fmacro-backtrace-limit=0 to "
584              "see all)";
585   emitBasicNote(Message.str());
586 
587   for (auto I = LocationStack.rend() - MacroEndMessages,
588             E = LocationStack.rend();
589        I != E; ++I)
590     emitSingleMacroExpansion(FullSourceLoc(*I, SM), Level, Ranges);
591 }
592 
593 DiagnosticNoteRenderer::~DiagnosticNoteRenderer() = default;
594 
595 void DiagnosticNoteRenderer::emitIncludeLocation(FullSourceLoc Loc,
596                                                  PresumedLoc PLoc) {
597   // Generate a note indicating the include location.
598   SmallString<200> MessageStorage;
599   llvm::raw_svector_ostream Message(MessageStorage);
600   Message << "in file included from " << PLoc.getFilename() << ':'
601           << PLoc.getLine() << ":";
602   emitNote(Loc, Message.str());
603 }
604 
605 void DiagnosticNoteRenderer::emitImportLocation(FullSourceLoc Loc,
606                                                 PresumedLoc PLoc,
607                                                 StringRef ModuleName) {
608   // Generate a note indicating the include location.
609   SmallString<200> MessageStorage;
610   llvm::raw_svector_ostream Message(MessageStorage);
611   Message << "in module '" << ModuleName;
612   if (PLoc.isValid())
613     Message << "' imported from " << PLoc.getFilename() << ':'
614             << PLoc.getLine();
615   Message << ":";
616   emitNote(Loc, Message.str());
617 }
618 
619 void DiagnosticNoteRenderer::emitBuildingModuleLocation(FullSourceLoc Loc,
620                                                         PresumedLoc PLoc,
621                                                         StringRef ModuleName) {
622   // Generate a note indicating the include location.
623   SmallString<200> MessageStorage;
624   llvm::raw_svector_ostream Message(MessageStorage);
625   if (PLoc.isValid())
626     Message << "while building module '" << ModuleName << "' imported from "
627             << PLoc.getFilename() << ':' << PLoc.getLine() << ":";
628   else
629     Message << "while building module '" << ModuleName << "':";
630   emitNote(Loc, Message.str());
631 }
632