PrintfFormatString.cpp revision e729acbba75903f42e79e72e46cdebe3f4c35521
1//= PrintfFormatStrings.cpp - Analysis of printf format strings --*- C++ -*-==// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// Handling of format string in printf and friends. The structure of format 11// strings for fprintf() are described in C99 7.19.6.1. 12// 13//===----------------------------------------------------------------------===// 14 15#include "clang/Analysis/Analyses/PrintfFormatString.h" 16 17using namespace clang; 18using namespace analyze_printf; 19 20namespace { 21class FormatSpecifierResult { 22 FormatSpecifier FS; 23 const char *Start; 24 bool HasError; 25public: 26 FormatSpecifierResult(bool err = false) 27 : Start(0), HasError(err) {} 28 FormatSpecifierResult(const char *start, 29 const FormatSpecifier &fs) 30 : FS(fs), Start(start), HasError(false) {} 31 32 33 const char *getStart() const { return Start; } 34 bool hasError() const { return HasError; } 35 bool hasValue() const { return Start != 0; } 36 const FormatSpecifier &getValue() const { 37 assert(hasValue()); 38 return FS; 39 } 40 const FormatSpecifier &getValue() { return FS; } 41}; 42} // end anonymous namespace 43 44template <typename T> 45class UpdateOnReturn { 46 T &ValueToUpdate; 47 const T &ValueToCopy; 48public: 49 UpdateOnReturn(T &valueToUpdate, const T &valueToCopy) 50 : ValueToUpdate(valueToUpdate), ValueToCopy(valueToCopy) {} 51 52 ~UpdateOnReturn() { 53 ValueToUpdate = ValueToCopy; 54 } 55}; 56 57static OptionalAmount ParseAmount(const char *&Beg, const char *E) { 58 const char *I = Beg; 59 UpdateOnReturn <const char*> UpdateBeg(Beg, I); 60 61 bool foundDigits = false; 62 unsigned accumulator = 0; 63 64 for ( ; I != E; ++I) { 65 char c = *I; 66 if (c >= '0' && c <= '9') { 67 foundDigits = true; 68 accumulator += (accumulator * 10) + (c - '0'); 69 continue; 70 } 71 72 if (foundDigits) 73 return OptionalAmount(accumulator); 74 75 if (c == '*') 76 return OptionalAmount(OptionalAmount::Arg); 77 78 break; 79 } 80 81 return OptionalAmount(); 82} 83 84static FormatSpecifierResult ParseFormatSpecifier(FormatStringHandler &H, 85 const char *&Beg, const char *E) { 86 87 const char *I = Beg; 88 const char *Start = 0; 89 UpdateOnReturn <const char*> UpdateBeg(Beg, I); 90 91 // Look for a '%' character that indicates the start of a format specifier. 92 for ( ; I != E ; ++I) { 93 char c = *I; 94 if (c == '\0') { 95 // Detect spurious null characters, which are likely errors. 96 H.HandleNullChar(I); 97 return true; 98 } 99 if (c == '%') { 100 Start = I++; // Record the start of the format specifier. 101 break; 102 } 103 } 104 105 // No format specifier found? 106 if (!Start) 107 return false; 108 109 if (I == E) { 110 // No more characters left? 111 H.HandleIncompleteFormatSpecifier(Start, E); 112 return true; 113 } 114 115 FormatSpecifier FS; 116 117 // Look for flags (if any). 118 bool hasMore = true; 119 for ( ; I != E; ++I) { 120 switch (*I) { 121 default: hasMore = false; break; 122 case '-': FS.setIsLeftJustified(); break; 123 case '+': FS.setHasPlusPrefix(); break; 124 case ' ': FS.setHasSpacePrefix(); break; 125 case '#': FS.setHasAlternativeForm(); break; 126 case '0': FS.setHasLeadingZeros(); break; 127 } 128 if (!hasMore) 129 break; 130 } 131 132 if (I == E) { 133 // No more characters left? 134 H.HandleIncompleteFormatSpecifier(Start, E); 135 return true; 136 } 137 138 // Look for the field width (if any). 139 FS.setFieldWidth(ParseAmount(I, E)); 140 141 if (I == E) { 142 // No more characters left? 143 H.HandleIncompleteFormatSpecifier(Start, E); 144 return true; 145 } 146 147 // Look for the precision (if any). 148 if (*I == '.') { 149 const char *startPrecision = I++; 150 if (I == E) { 151 H.HandleIncompletePrecision(I - 1); 152 return true; 153 } 154 155 FS.setPrecision(ParseAmount(I, E)); 156 157 if (I == E) { 158 // No more characters left? 159 H.HandleIncompletePrecision(startPrecision); 160 return true; 161 } 162 } 163 164 // Look for the length modifier. 165 LengthModifier lm = None; 166 switch (*I) { 167 default: 168 break; 169 case 'h': 170 ++I; 171 lm = (I != E && *I == 'h') ? ++I, AsChar : AsShort; 172 break; 173 case 'l': 174 ++I; 175 lm = (I != E && *I == 'l') ? ++I, AsLongLong : AsLong; 176 break; 177 case 'j': lm = AsIntMax; ++I; break; 178 case 'z': lm = AsSizeT; ++I; break; 179 case 't': lm = AsPtrDiff; ++I; break; 180 case 'L': lm = AsLongDouble; ++I; break; 181 } 182 FS.setLengthModifier(lm); 183 184 if (I == E) { 185 // No more characters left? 186 H.HandleIncompleteFormatSpecifier(Start, E); 187 return true; 188 } 189 190 // Finally, look for the conversion specifier. 191 const char *conversionPosition = I++; 192 ConversionSpecifier::Kind k; 193 switch (*conversionPosition) { 194 default: 195 H.HandleInvalidConversionSpecifier(conversionPosition); 196 return true; 197 // C99: 7.19.6.1 (section 8). 198 case 'd': k = ConversionSpecifier::dArg; break; 199 case 'i': k = ConversionSpecifier::iArg; break; 200 case 'o': k = ConversionSpecifier::oArg; break; 201 case 'u': k = ConversionSpecifier::uArg; break; 202 case 'x': k = ConversionSpecifier::xArg; break; 203 case 'X': k = ConversionSpecifier::XArg; break; 204 case 'f': k = ConversionSpecifier::fArg; break; 205 case 'F': k = ConversionSpecifier::FArg; break; 206 case 'e': k = ConversionSpecifier::eArg; break; 207 case 'E': k = ConversionSpecifier::EArg; break; 208 case 'g': k = ConversionSpecifier::gArg; break; 209 case 'G': k = ConversionSpecifier::GArg; break; 210 case 'a': k = ConversionSpecifier::aArg; break; 211 case 'A': k = ConversionSpecifier::AArg; break; 212 case 'c': k = ConversionSpecifier::IntAsCharArg; break; 213 case 's': k = ConversionSpecifier::CStrArg; break; 214 case 'p': k = ConversionSpecifier::VoidPtrArg; break; 215 case 'n': k = ConversionSpecifier::OutIntPtrArg; break; 216 case '%': k = ConversionSpecifier::PercentArg; break; 217 // Objective-C. 218 case '@': k = ConversionSpecifier::ObjCObjArg; break; 219 } 220 FS.setConversionSpecifier(ConversionSpecifier(conversionPosition, k)); 221 return FormatSpecifierResult(Start, FS); 222} 223 224namespace clang { namespace analyze_printf { 225bool ParseFormatString(FormatStringHandler &H, 226 const char *I, const char *E) { 227 // Keep looking for a format specifier until we have exhausted the string. 228 while (I != E) { 229 const FormatSpecifierResult &FSR = ParseFormatSpecifier(H, I, E); 230 // Did an error of any kind occur when parsing the specifier? If so, 231 // don't do any more processing. 232 if (FSR.hasError()) 233 return true;; 234 // Done processing the string? 235 if (!FSR.hasValue()) 236 break; 237 // We have a format specifier. Pass it to the callback. 238 if (!H.HandleFormatSpecifier(FSR.getValue(), FSR.getStart(), 239 I - FSR.getStart())) 240 return false; 241 } 242 assert(I == E && "Format string not exhausted"); 243 return false; 244} 245}} 246 247FormatStringHandler::~FormatStringHandler() {} 248