path: root/contrib/libs/llvm12/lib/Support/SourceMgr.cpp

//===- SourceMgr.cpp - Manager for Simple Source Buffers & Diagnostics ----===// 
// 
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 
// See https://llvm.org/LICENSE.txt for license information. 
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 
// 
//===----------------------------------------------------------------------===// 
// 
// This file implements the SourceMgr class.  This class is used as a simple 
// substrate for diagnostics, #include handling, and other low level things for 
// simple parsers. 
// 
//===----------------------------------------------------------------------===// 
 
#include "llvm/Support/SourceMgr.h" 
#include "llvm/ADT/ArrayRef.h" 
#include "llvm/ADT/STLExtras.h" 
#include "llvm/ADT/SmallVector.h" 
#include "llvm/ADT/StringRef.h" 
#include "llvm/ADT/Twine.h" 
#include "llvm/Support/ErrorOr.h" 
#include "llvm/Support/Locale.h" 
#include "llvm/Support/MemoryBuffer.h" 
#include "llvm/Support/Path.h" 
#include "llvm/Support/SMLoc.h" 
#include "llvm/Support/WithColor.h" 
#include "llvm/Support/raw_ostream.h" 
#include <algorithm> 
#include <cassert> 
#include <cstddef> 
#include <limits> 
#include <memory> 
#include <string> 
#include <utility> 
 
using namespace llvm; 
 
static const size_t TabStop = 8; 
 
unsigned SourceMgr::AddIncludeFile(const std::string &Filename, 
                                   SMLoc IncludeLoc, 
                                   std::string &IncludedFile) { 
  IncludedFile = Filename; 
  ErrorOr<std::unique_ptr<MemoryBuffer>> NewBufOrErr = 
      MemoryBuffer::getFile(IncludedFile); 
 
  // If the file didn't exist directly, see if it's in an include path. 
  for (unsigned i = 0, e = IncludeDirectories.size(); i != e && !NewBufOrErr; 
       ++i) { 
    IncludedFile = 
        IncludeDirectories[i] + sys::path::get_separator().data() + Filename; 
    NewBufOrErr = MemoryBuffer::getFile(IncludedFile); 
  } 
 
  if (!NewBufOrErr) 
    return 0; 
 
  return AddNewSourceBuffer(std::move(*NewBufOrErr), IncludeLoc); 
} 
 
unsigned SourceMgr::FindBufferContainingLoc(SMLoc Loc) const { 
  for (unsigned i = 0, e = Buffers.size(); i != e; ++i) 
    if (Loc.getPointer() >= Buffers[i].Buffer->getBufferStart() && 
        // Use <= here so that a pointer to the null at the end of the buffer 
        // is included as part of the buffer. 
        Loc.getPointer() <= Buffers[i].Buffer->getBufferEnd()) 
      return i + 1; 
  return 0; 
} 
 
template <typename T> 
static std::vector<T> &GetOrCreateOffsetCache(void *&OffsetCache, 
                                              MemoryBuffer *Buffer) { 
  if (OffsetCache) 
    return *static_cast<std::vector<T> *>(OffsetCache); 
 
  // Lazily fill in the offset cache. 
  auto *Offsets = new std::vector<T>(); 
  size_t Sz = Buffer->getBufferSize(); 
  assert(Sz <= std::numeric_limits<T>::max()); 
  StringRef S = Buffer->getBuffer(); 
  for (size_t N = 0; N < Sz; ++N) { 
    if (S[N] == '\n') 
      Offsets->push_back(static_cast<T>(N)); 
  } 
 
  OffsetCache = Offsets; 
  return *Offsets; 
} 
 
template <typename T> 
unsigned SourceMgr::SrcBuffer::getLineNumberSpecialized(const char *Ptr) const { 
  std::vector<T> &Offsets = 
      GetOrCreateOffsetCache<T>(OffsetCache, Buffer.get()); 
 
  const char *BufStart = Buffer->getBufferStart(); 
  assert(Ptr >= BufStart && Ptr <= Buffer->getBufferEnd()); 
  ptrdiff_t PtrDiff = Ptr - BufStart; 
  assert(PtrDiff >= 0 && 
         static_cast<size_t>(PtrDiff) <= std::numeric_limits<T>::max()); 
  T PtrOffset = static_cast<T>(PtrDiff); 
 
  // llvm::lower_bound gives the number of EOL before PtrOffset. Add 1 to get 
  // the line number. 
  return llvm::lower_bound(Offsets, PtrOffset) - Offsets.begin() + 1; 
} 
 
/// Look up a given \p Ptr in in the buffer, determining which line it came 
/// from. 
unsigned SourceMgr::SrcBuffer::getLineNumber(const char *Ptr) const { 
  size_t Sz = Buffer->getBufferSize(); 
  if (Sz <= std::numeric_limits<uint8_t>::max()) 
    return getLineNumberSpecialized<uint8_t>(Ptr); 
  else if (Sz <= std::numeric_limits<uint16_t>::max()) 
    return getLineNumberSpecialized<uint16_t>(Ptr); 
  else if (Sz <= std::numeric_limits<uint32_t>::max()) 
    return getLineNumberSpecialized<uint32_t>(Ptr); 
  else 
    return getLineNumberSpecialized<uint64_t>(Ptr); 
} 
 
template <typename T> 
const char *SourceMgr::SrcBuffer::getPointerForLineNumberSpecialized( 
    unsigned LineNo) const { 
  std::vector<T> &Offsets = 
      GetOrCreateOffsetCache<T>(OffsetCache, Buffer.get()); 
 
  // We start counting line and column numbers from 1. 
  if (LineNo != 0) 
    --LineNo; 
 
  const char *BufStart = Buffer->getBufferStart(); 
 
  // The offset cache contains the location of the \n for the specified line, 
  // we want the start of the line.  As such, we look for the previous entry. 
  if (LineNo == 0) 
    return BufStart; 
  if (LineNo > Offsets.size()) 
    return nullptr; 
  return BufStart + Offsets[LineNo - 1] + 1; 
} 
 
/// Return a pointer to the first character of the specified line number or 
/// null if the line number is invalid. 
const char * 
SourceMgr::SrcBuffer::getPointerForLineNumber(unsigned LineNo) const { 
  size_t Sz = Buffer->getBufferSize(); 
  if (Sz <= std::numeric_limits<uint8_t>::max()) 
    return getPointerForLineNumberSpecialized<uint8_t>(LineNo); 
  else if (Sz <= std::numeric_limits<uint16_t>::max()) 
    return getPointerForLineNumberSpecialized<uint16_t>(LineNo); 
  else if (Sz <= std::numeric_limits<uint32_t>::max()) 
    return getPointerForLineNumberSpecialized<uint32_t>(LineNo); 
  else 
    return getPointerForLineNumberSpecialized<uint64_t>(LineNo); 
} 
 
SourceMgr::SrcBuffer::SrcBuffer(SourceMgr::SrcBuffer &&Other) 
    : Buffer(std::move(Other.Buffer)), OffsetCache(Other.OffsetCache), 
      IncludeLoc(Other.IncludeLoc) { 
  Other.OffsetCache = nullptr; 
} 
 
SourceMgr::SrcBuffer::~SrcBuffer() { 
  if (OffsetCache) { 
    size_t Sz = Buffer->getBufferSize(); 
    if (Sz <= std::numeric_limits<uint8_t>::max()) 
      delete static_cast<std::vector<uint8_t> *>(OffsetCache); 
    else if (Sz <= std::numeric_limits<uint16_t>::max()) 
      delete static_cast<std::vector<uint16_t> *>(OffsetCache); 
    else if (Sz <= std::numeric_limits<uint32_t>::max()) 
      delete static_cast<std::vector<uint32_t> *>(OffsetCache); 
    else 
      delete static_cast<std::vector<uint64_t> *>(OffsetCache); 
    OffsetCache = nullptr; 
  } 
} 
 
std::pair<unsigned, unsigned> 
SourceMgr::getLineAndColumn(SMLoc Loc, unsigned BufferID) const { 
  if (!BufferID) 
    BufferID = FindBufferContainingLoc(Loc); 
  assert(BufferID && "Invalid location!");
 
  auto &SB = getBufferInfo(BufferID); 
  const char *Ptr = Loc.getPointer(); 
 
  unsigned LineNo = SB.getLineNumber(Ptr); 
  const char *BufStart = SB.Buffer->getBufferStart(); 
  size_t NewlineOffs = StringRef(BufStart, Ptr - BufStart).find_last_of("\n\r"); 
  if (NewlineOffs == StringRef::npos) 
    NewlineOffs = ~(size_t)0; 
  return std::make_pair(LineNo, Ptr - BufStart - NewlineOffs); 
} 
 
// FIXME: Note that the formatting of source locations is spread between
// multiple functions, some in SourceMgr and some in SMDiagnostic. A better
// solution would be a general-purpose source location formatter
// in one of those two classes, or possibly in SMLoc.

/// Get a string with the source location formatted in the standard
/// style, but without the line offset. If \p IncludePath is true, the path
/// is included. If false, only the file name and extension are included.
std::string SourceMgr::getFormattedLocationNoOffset(SMLoc Loc,
                                                    bool IncludePath) const {
  auto BufferID = FindBufferContainingLoc(Loc);
  assert(BufferID && "Invalid location!");
  auto FileSpec = getBufferInfo(BufferID).Buffer->getBufferIdentifier();

  if (IncludePath) {
    return FileSpec.str() + ":" + std::to_string(FindLineNumber(Loc, BufferID));
  } else {
    auto I = FileSpec.find_last_of("/\\");
    I = (I == FileSpec.size()) ? 0 : (I + 1);
    return FileSpec.substr(I).str() + ":" +
           std::to_string(FindLineNumber(Loc, BufferID));
  }
}

/// Given a line and column number in a mapped buffer, turn it into an SMLoc. 
/// This will return a null SMLoc if the line/column location is invalid. 
SMLoc SourceMgr::FindLocForLineAndColumn(unsigned BufferID, unsigned LineNo, 
                                         unsigned ColNo) { 
  auto &SB = getBufferInfo(BufferID); 
  const char *Ptr = SB.getPointerForLineNumber(LineNo); 
  if (!Ptr) 
    return SMLoc(); 
 
  // We start counting line and column numbers from 1. 
  if (ColNo != 0) 
    --ColNo; 
 
  // If we have a column number, validate it. 
  if (ColNo) { 
    // Make sure the location is within the current line. 
    if (Ptr + ColNo > SB.Buffer->getBufferEnd()) 
      return SMLoc(); 
 
    // Make sure there is no newline in the way. 
    if (StringRef(Ptr, ColNo).find_first_of("\n\r") != StringRef::npos) 
      return SMLoc(); 
 
    Ptr += ColNo; 
  } 
 
  return SMLoc::getFromPointer(Ptr); 
} 
 
void SourceMgr::PrintIncludeStack(SMLoc IncludeLoc, raw_ostream &OS) const { 
  if (IncludeLoc == SMLoc()) 
    return; // Top of stack. 
 
  unsigned CurBuf = FindBufferContainingLoc(IncludeLoc); 
  assert(CurBuf && "Invalid or unspecified location!"); 
 
  PrintIncludeStack(getBufferInfo(CurBuf).IncludeLoc, OS); 
 
  OS << "Included from " << getBufferInfo(CurBuf).Buffer->getBufferIdentifier() 
     << ":" << FindLineNumber(IncludeLoc, CurBuf) << ":\n"; 
} 
 
SMDiagnostic SourceMgr::GetMessage(SMLoc Loc, SourceMgr::DiagKind Kind, 
                                   const Twine &Msg, ArrayRef<SMRange> Ranges, 
                                   ArrayRef<SMFixIt> FixIts) const { 
  // First thing to do: find the current buffer containing the specified 
  // location to pull out the source line. 
  SmallVector<std::pair<unsigned, unsigned>, 4> ColRanges; 
  std::pair<unsigned, unsigned> LineAndCol; 
  StringRef BufferID = "<unknown>"; 
  StringRef LineStr;
 
  if (Loc.isValid()) { 
    unsigned CurBuf = FindBufferContainingLoc(Loc); 
    assert(CurBuf && "Invalid or unspecified location!"); 
 
    const MemoryBuffer *CurMB = getMemoryBuffer(CurBuf); 
    BufferID = CurMB->getBufferIdentifier(); 
 
    // Scan backward to find the start of the line. 
    const char *LineStart = Loc.getPointer(); 
    const char *BufStart = CurMB->getBufferStart(); 
    while (LineStart != BufStart && LineStart[-1] != '\n' && 
           LineStart[-1] != '\r') 
      --LineStart; 
 
    // Get the end of the line. 
    const char *LineEnd = Loc.getPointer(); 
    const char *BufEnd = CurMB->getBufferEnd(); 
    while (LineEnd != BufEnd && LineEnd[0] != '\n' && LineEnd[0] != '\r') 
      ++LineEnd; 
    LineStr = StringRef(LineStart, LineEnd - LineStart);
 
    // Convert any ranges to column ranges that only intersect the line of the 
    // location. 
    for (unsigned i = 0, e = Ranges.size(); i != e; ++i) { 
      SMRange R = Ranges[i]; 
      if (!R.isValid()) 
        continue; 
 
      // If the line doesn't contain any part of the range, then ignore it. 
      if (R.Start.getPointer() > LineEnd || R.End.getPointer() < LineStart) 
        continue; 
 
      // Ignore pieces of the range that go onto other lines. 
      if (R.Start.getPointer() < LineStart) 
        R.Start = SMLoc::getFromPointer(LineStart); 
      if (R.End.getPointer() > LineEnd) 
        R.End = SMLoc::getFromPointer(LineEnd); 
 
      // Translate from SMLoc ranges to column ranges. 
      // FIXME: Handle multibyte characters. 
      ColRanges.push_back(std::make_pair(R.Start.getPointer() - LineStart, 
                                         R.End.getPointer() - LineStart)); 
    } 
 
    LineAndCol = getLineAndColumn(Loc, CurBuf); 
  } 
 
  return SMDiagnostic(*this, Loc, BufferID, LineAndCol.first, 
                      LineAndCol.second - 1, Kind, Msg.str(), LineStr, 
                      ColRanges, FixIts); 
} 
 
void SourceMgr::PrintMessage(raw_ostream &OS, const SMDiagnostic &Diagnostic, 
                             bool ShowColors) const { 
  // Report the message with the diagnostic handler if present. 
  if (DiagHandler) { 
    DiagHandler(Diagnostic, DiagContext); 
    return; 
  } 
 
  if (Diagnostic.getLoc().isValid()) { 
    unsigned CurBuf = FindBufferContainingLoc(Diagnostic.getLoc()); 
    assert(CurBuf && "Invalid or unspecified location!"); 
    PrintIncludeStack(getBufferInfo(CurBuf).IncludeLoc, OS); 
  } 
 
  Diagnostic.print(nullptr, OS, ShowColors); 
} 
 
void SourceMgr::PrintMessage(raw_ostream &OS, SMLoc Loc, 
                             SourceMgr::DiagKind Kind, const Twine &Msg, 
                             ArrayRef<SMRange> Ranges, ArrayRef<SMFixIt> FixIts, 
                             bool ShowColors) const { 
  PrintMessage(OS, GetMessage(Loc, Kind, Msg, Ranges, FixIts), ShowColors); 
} 
 
void SourceMgr::PrintMessage(SMLoc Loc, SourceMgr::DiagKind Kind, 
                             const Twine &Msg, ArrayRef<SMRange> Ranges, 
                             ArrayRef<SMFixIt> FixIts, bool ShowColors) const { 
  PrintMessage(errs(), Loc, Kind, Msg, Ranges, FixIts, ShowColors); 
} 
 
//===----------------------------------------------------------------------===// 
// SMFixIt Implementation 
//===----------------------------------------------------------------------===// 
 
SMFixIt::SMFixIt(SMRange R, const Twine &Replacement) 
    : Range(R), Text(Replacement.str()) { 
  assert(R.isValid()); 
} 
 
//===----------------------------------------------------------------------===// 
// SMDiagnostic Implementation 
//===----------------------------------------------------------------------===// 
 
SMDiagnostic::SMDiagnostic(const SourceMgr &sm, SMLoc L, StringRef FN, int Line, 
                           int Col, SourceMgr::DiagKind Kind, StringRef Msg, 
                           StringRef LineStr, 
                           ArrayRef<std::pair<unsigned, unsigned>> Ranges, 
                           ArrayRef<SMFixIt> Hints) 
    : SM(&sm), Loc(L), Filename(std::string(FN)), LineNo(Line), ColumnNo(Col), 
      Kind(Kind), Message(Msg), LineContents(LineStr), Ranges(Ranges.vec()),
      FixIts(Hints.begin(), Hints.end()) {
  llvm::sort(FixIts); 
} 
 
static void buildFixItLine(std::string &CaretLine, std::string &FixItLine, 
                           ArrayRef<SMFixIt> FixIts, 
                           ArrayRef<char> SourceLine) { 
  if (FixIts.empty()) 
    return; 
 
  const char *LineStart = SourceLine.begin(); 
  const char *LineEnd = SourceLine.end(); 
 
  size_t PrevHintEndCol = 0; 
 
  for (const llvm::SMFixIt &Fixit : FixIts) {
    // If the fixit contains a newline or tab, ignore it. 
    if (Fixit.getText().find_first_of("\n\r\t") != StringRef::npos)
      continue; 
 
    SMRange R = Fixit.getRange();
 
    // If the line doesn't contain any part of the range, then ignore it. 
    if (R.Start.getPointer() > LineEnd || R.End.getPointer() < LineStart) 
      continue; 
 
    // Translate from SMLoc to column. 
    // Ignore pieces of the range that go onto other lines. 
    // FIXME: Handle multibyte characters in the source line. 
    unsigned FirstCol; 
    if (R.Start.getPointer() < LineStart) 
      FirstCol = 0; 
    else 
      FirstCol = R.Start.getPointer() - LineStart; 
 
    // If we inserted a long previous hint, push this one forwards, and add 
    // an extra space to show that this is not part of the previous 
    // completion. This is sort of the best we can do when two hints appear 
    // to overlap. 
    // 
    // Note that if this hint is located immediately after the previous 
    // hint, no space will be added, since the location is more important. 
    unsigned HintCol = FirstCol; 
    if (HintCol < PrevHintEndCol) 
      HintCol = PrevHintEndCol + 1; 
 
    // FIXME: This assertion is intended to catch unintended use of multibyte 
    // characters in fixits. If we decide to do this, we'll have to track 
    // separate byte widths for the source and fixit lines. 
    assert((size_t)sys::locale::columnWidth(Fixit.getText()) ==
           Fixit.getText().size());
 
    // This relies on one byte per column in our fixit hints. 
    unsigned LastColumnModified = HintCol + Fixit.getText().size();
    if (LastColumnModified > FixItLine.size()) 
      FixItLine.resize(LastColumnModified, ' '); 
 
    llvm::copy(Fixit.getText(), FixItLine.begin() + HintCol);
 
    PrevHintEndCol = LastColumnModified; 
 
    // For replacements, mark the removal range with '~'. 
    // FIXME: Handle multibyte characters in the source line. 
    unsigned LastCol; 
    if (R.End.getPointer() >= LineEnd) 
      LastCol = LineEnd - LineStart; 
    else 
      LastCol = R.End.getPointer() - LineStart; 
 
    std::fill(&CaretLine[FirstCol], &CaretLine[LastCol], '~'); 
  } 
} 
 
static void printSourceLine(raw_ostream &S, StringRef LineContents) { 
  // Print out the source line one character at a time, so we can expand tabs. 
  for (unsigned i = 0, e = LineContents.size(), OutCol = 0; i != e; ++i) { 
    size_t NextTab = LineContents.find('\t', i); 
    // If there were no tabs left, print the rest, we are done. 
    if (NextTab == StringRef::npos) { 
      S << LineContents.drop_front(i); 
      break; 
    } 
 
    // Otherwise, print from i to NextTab. 
    S << LineContents.slice(i, NextTab); 
    OutCol += NextTab - i; 
    i = NextTab; 
 
    // If we have a tab, emit at least one space, then round up to 8 columns. 
    do { 
      S << ' '; 
      ++OutCol; 
    } while ((OutCol % TabStop) != 0); 
  } 
  S << '\n'; 
} 
 
static bool isNonASCII(char c) { return c & 0x80; } 
 
void SMDiagnostic::print(const char *ProgName, raw_ostream &OS, bool ShowColors, 
                         bool ShowKindLabel) const { 
  ColorMode Mode = ShowColors ? ColorMode::Auto : ColorMode::Disable; 
 
  { 
    WithColor S(OS, raw_ostream::SAVEDCOLOR, true, false, Mode); 
 
    if (ProgName && ProgName[0]) 
      S << ProgName << ": "; 
 
    if (!Filename.empty()) { 
      if (Filename == "-") 
        S << "<stdin>"; 
      else 
        S << Filename; 
 
      if (LineNo != -1) { 
        S << ':' << LineNo; 
        if (ColumnNo != -1) 
          S << ':' << (ColumnNo + 1); 
      } 
      S << ": "; 
    } 
  } 
 
  if (ShowKindLabel) { 
    switch (Kind) { 
    case SourceMgr::DK_Error: 
      WithColor::error(OS, "", !ShowColors); 
      break; 
    case SourceMgr::DK_Warning: 
      WithColor::warning(OS, "", !ShowColors); 
      break; 
    case SourceMgr::DK_Note: 
      WithColor::note(OS, "", !ShowColors); 
      break; 
    case SourceMgr::DK_Remark: 
      WithColor::remark(OS, "", !ShowColors); 
      break; 
    } 
  } 
 
  WithColor(OS, raw_ostream::SAVEDCOLOR, true, false, Mode) << Message << '\n'; 
 
  if (LineNo == -1 || ColumnNo == -1) 
    return; 
 
  // FIXME: If there are multibyte or multi-column characters in the source, all 
  // our ranges will be wrong. To do this properly, we'll need a byte-to-column 
  // map like Clang's TextDiagnostic. For now, we'll just handle tabs by 
  // expanding them later, and bail out rather than show incorrect ranges and 
  // misaligned fixits for any other odd characters. 
  if (any_of(LineContents, isNonASCII)) {
    printSourceLine(OS, LineContents); 
    return; 
  } 
  size_t NumColumns = LineContents.size(); 
 
  // Build the line with the caret and ranges. 
  std::string CaretLine(NumColumns + 1, ' '); 
 
  // Expand any ranges. 
  for (const std::pair<unsigned, unsigned> &R : Ranges)
    std::fill(&CaretLine[R.first], 
              &CaretLine[std::min((size_t)R.second, CaretLine.size())], '~'); 
 
  // Add any fix-its. 
  // FIXME: Find the beginning of the line properly for multibyte characters. 
  std::string FixItInsertionLine; 
  buildFixItLine( 
      CaretLine, FixItInsertionLine, FixIts, 
      makeArrayRef(Loc.getPointer() - ColumnNo, LineContents.size())); 
 
  // Finally, plop on the caret. 
  if (unsigned(ColumnNo) <= NumColumns) 
    CaretLine[ColumnNo] = '^'; 
  else 
    CaretLine[NumColumns] = '^'; 
 
  // ... and remove trailing whitespace so the output doesn't wrap for it.  We 
  // know that the line isn't completely empty because it has the caret in it at 
  // least. 
  CaretLine.erase(CaretLine.find_last_not_of(' ') + 1); 
 
  printSourceLine(OS, LineContents); 
 
  { 
    ColorMode Mode = ShowColors ? ColorMode::Auto : ColorMode::Disable; 
    WithColor S(OS, raw_ostream::GREEN, true, false, Mode); 
 
    // Print out the caret line, matching tabs in the source line. 
    for (unsigned i = 0, e = CaretLine.size(), OutCol = 0; i != e; ++i) { 
      if (i >= LineContents.size() || LineContents[i] != '\t') { 
        S << CaretLine[i]; 
        ++OutCol; 
        continue; 
      } 
 
      // Okay, we have a tab.  Insert the appropriate number of characters. 
      do { 
        S << CaretLine[i]; 
        ++OutCol; 
      } while ((OutCol % TabStop) != 0); 
    } 
    S << '\n'; 
  } 
 
  // Print out the replacement line, matching tabs in the source line. 
  if (FixItInsertionLine.empty()) 
    return; 
 
  for (size_t i = 0, e = FixItInsertionLine.size(), OutCol = 0; i < e; ++i) { 
    if (i >= LineContents.size() || LineContents[i] != '\t') { 
      OS << FixItInsertionLine[i]; 
      ++OutCol; 
      continue; 
    } 
 
    // Okay, we have a tab.  Insert the appropriate number of characters. 
    do { 
      OS << FixItInsertionLine[i]; 
      // FIXME: This is trying not to break up replacements, but then to re-sync 
      // with the tabs between replacements. This will fail, though, if two 
      // fix-it replacements are exactly adjacent, or if a fix-it contains a 
      // space. Really we should be precomputing column widths, which we'll 
      // need anyway for multibyte chars. 
      if (FixItInsertionLine[i] != ' ') 
        ++i; 
      ++OutCol; 
    } while (((OutCol % TabStop) != 0) && i != e); 
  } 
  OS << '\n'; 
}