Add the main scanf-parsing logic that I meant to include in my previous commit.

llvm-svn: 108502

clang/lib/Analysis/ScanfFormatString.cpp

+//= ScanfFormatString.cpp - Analysis of printf format strings --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Handling of format string in scanf and friends.  The structure of format
+// strings for fscanf() are described in C99 7.19.6.2.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/FormatString.h"
+#include "FormatStringParsing.h"
+
+using clang::analyze_format_string::ArgTypeResult;
+using clang::analyze_format_string::FormatStringHandler;
+using clang::analyze_format_string::LengthModifier;
+using clang::analyze_format_string::OptionalAmount;
+using clang::analyze_scanf::ConversionSpecifier;
+using clang::analyze_scanf::ScanfSpecifier;
+
+typedef clang::analyze_format_string::SpecifierResult<ScanfSpecifier>
+        ScanfSpecifierResult;
+
+static bool ParseScanList(FormatStringHandler &H,
+                          ConversionSpecifier &CS,
+                          const char *&Beg, const char *E) {
+  const char *I = Beg;
+  const char *start = I - 1;
+  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
+
+  // No more characters?
+  if (I == E) {
+    H.HandleIncompleteScanList(start, I);
+    return true;
+  }
+  
+  // Special case: ']' is the first character.
+  if (*I == ']') {
+    if (++I == E) {
+      H.HandleIncompleteScanList(start, I);
+      return true;
+    }
+  }
+
+  // Look for a ']' character which denotes the end of the scan list.
+  while (*I != ']') {
+    if (++I == E) {
+      H.HandleIncompleteScanList(start, I);
+      return true;
+    }
+  }    
+
+  CS.setEndScanList(I);
+  return false;
+}
+
+// FIXME: Much of this is copy-paste from ParsePrintfSpecifier.
+// We can possibly refactor.
+static ScanfSpecifierResult ParseScanfSpecifier(FormatStringHandler &H,
+                                                const char *&Beg,
+                                                const char *E,
+                                                unsigned &argIndex) {
+  
+  using namespace clang::analyze_scanf;
+  const char *I = Beg;
+  const char *Start = 0;
+  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
+
+    // Look for a '%' character that indicates the start of a format specifier.
+  for ( ; I != E ; ++I) {
+    char c = *I;
+    if (c == '\0') {
+        // Detect spurious null characters, which are likely errors.
+      H.HandleNullChar(I);
+      return true;
+    }
+    if (c == '%') {
+      Start = I++;  // Record the start of the format specifier.
+      break;
+    }
+  }
+  
+    // No format specifier found?
+  if (!Start)
+    return false;
+  
+  if (I == E) {
+      // No more characters left?
+    H.HandleIncompleteSpecifier(Start, E - Start);
+    return true;
+  }
+  
+  ScanfSpecifier FS;
+  if (ParseArgPosition(H, FS, Start, I, E))
+    return true;
+
+  if (I == E) {
+      // No more characters left?
+    H.HandleIncompleteSpecifier(Start, E - Start);
+    return true;
+  }
+  
+  // Look for '*' flag if it is present.
+  if (*I == '*') {
+    FS.setSuppressAssignment(I);
+    if (++I == E) {
+      H.HandleIncompleteSpecifier(Start, E - Start);
+      return true;
+    }
+  }
+  
+  // Look for the field width (if any).  Unlike printf, this is either
+  // a fixed integer or isn't present.
+  const OptionalAmount &Amt = clang::analyze_format_string::ParseAmount(I, E);
+  if (Amt.getHowSpecified() != OptionalAmount::NotSpecified) {
+    assert(Amt.getHowSpecified() == OptionalAmount::Constant);
+    FS.setFieldWidth(Amt);
+
+    if (I == E) {
+      // No more characters left?
+      H.HandleIncompleteSpecifier(Start, E - Start);
+      return true;
+    }
+  }
+  
+  // Look for the length modifier.
+  if (ParseLengthModifier(FS, I, E) && I == E) {
+      // No more characters left?
+    H.HandleIncompleteSpecifier(Start, E - Start);
+    return true;
+  }
+  
+  // Detect spurious null characters, which are likely errors.
+  if (*I == '\0') {
+    H.HandleNullChar(I);
+    return true;
+  }
+  
+  // Finally, look for the conversion specifier.
+  const char *conversionPosition = I++;
+  ConversionSpecifier::Kind k = ConversionSpecifier::InvalidSpecifier;
+  switch (*conversionPosition) {
+    default:
+      break;
+    case '%': k = ConversionSpecifier::PercentArg;   break;
+    case 'A': k = ConversionSpecifier::AArg; break;
+    case 'E': k = ConversionSpecifier::EArg; break;
+    case 'F': k = ConversionSpecifier::FArg; break;
+    case 'G': k = ConversionSpecifier::GArg; break;
+    case 'X': k = ConversionSpecifier::XArg; break;
+    case 'a': k = ConversionSpecifier::aArg; break;
+    case 'd': k = ConversionSpecifier::dArg; break;
+    case 'e': k = ConversionSpecifier::eArg; break;
+    case 'f': k = ConversionSpecifier::fArg; break;
+    case 'g': k = ConversionSpecifier::gArg; break;
+    case 'i': k = ConversionSpecifier::iArg; break;
+    case 'n': k = ConversionSpecifier::ConsumedSoFarArg; break;
+    case 'c': k = ConversionSpecifier::cArg; break;
+    case 'C': k = ConversionSpecifier::CArg; break;
+    case 'S': k = ConversionSpecifier::SArg; break;
+    case '[': k = ConversionSpecifier::ScanListArg; break;
+  }
+  ConversionSpecifier CS(conversionPosition, k);
+  if (k == ConversionSpecifier::ScanListArg) {
+    if (!ParseScanList(H, CS, I, E))
+      return true;
+  }
+  FS.setConversionSpecifier(CS);
+  if (CS.consumesDataArgument() && !FS.getSuppressAssignment()
+      && !FS.usesPositionalArg())
+    FS.setArgIndex(argIndex++);
+  
+  // FIXME: '%' and '*' doesn't make sense.  Issue a warning.
+  // FIXME: 'ConsumedSoFar' and '*' doesn't make sense.
+  
+  if (k == ConversionSpecifier::InvalidSpecifier) {
+    // Assume the conversion takes one argument.
+    return !H.HandleInvalidScanfConversionSpecifier(FS, Beg, I - Beg);
+  }
+  return ScanfSpecifierResult(Start, FS);
+}
+  
+bool clang::analyze_format_string::ParseScanfString(FormatStringHandler &H,
+                                                    const char *I,
+                                                    const char *E) {
+  
+  unsigned argIndex = 0;
+  
+  // Keep looking for a format specifier until we have exhausted the string.
+  while (I != E) {
+    const ScanfSpecifierResult &FSR = ParseScanfSpecifier(H, I, E, argIndex);
+    // Did a fail-stop error of any kind occur when parsing the specifier?
+    // If so, don't do any more processing.
+    if (FSR.shouldStop())
+      return true;;
+      // Did we exhaust the string or encounter an error that
+      // we can recover from?
+    if (!FSR.hasValue())
+      continue;
+      // We have a format specifier.  Pass it to the callback.
+    if (!H.HandleScanfSpecifier(FSR.getValue(), FSR.getStart(),
+                                I - FSR.getStart())) {
+      return true;
+    }
+  }
+  assert(I == E && "Format string not exhausted");
+  return false;
+}
+
+