PrintfFormatString.cpp revision 920439c0ec59e26196ce0defcda765c76c8b7778
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 clang::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, Beg); 74 75 if (c == '*') { 76 ++I; 77 return OptionalAmount(OptionalAmount::Arg, Beg); 78 } 79 80 break; 81 } 82 83 return OptionalAmount(); 84} 85 86static FormatSpecifierResult ParseFormatSpecifier(FormatStringHandler &H, 87 const char *&Beg, const char *E) { 88 89 const char *I = Beg; 90 const char *Start = 0; 91 UpdateOnReturn <const char*> UpdateBeg(Beg, I); 92 93 // Look for a '%' character that indicates the start of a format specifier. 94 for ( ; I != E ; ++I) { 95 char c = *I; 96 if (c == '\0') { 97 // Detect spurious null characters, which are likely errors. 98 H.HandleNullChar(I); 99 return true; 100 } 101 if (c == '%') { 102 Start = I++; // Record the start of the format specifier. 103 break; 104 } 105 } 106 107 // No format specifier found? 108 if (!Start) 109 return false; 110 111 if (I == E) { 112 // No more characters left? 113 H.HandleIncompleteFormatSpecifier(Start, E); 114 return true; 115 } 116 117 FormatSpecifier FS; 118 119 // Look for flags (if any). 120 bool hasMore = true; 121 for ( ; I != E; ++I) { 122 switch (*I) { 123 default: hasMore = false; break; 124 case '-': FS.setIsLeftJustified(); break; 125 case '+': FS.setHasPlusPrefix(); break; 126 case ' ': FS.setHasSpacePrefix(); break; 127 case '#': FS.setHasAlternativeForm(); break; 128 case '0': FS.setHasLeadingZeros(); break; 129 } 130 if (!hasMore) 131 break; 132 } 133 134 if (I == E) { 135 // No more characters left? 136 H.HandleIncompleteFormatSpecifier(Start, E); 137 return true; 138 } 139 140 // Look for the field width (if any). 141 FS.setFieldWidth(ParseAmount(I, E)); 142 143 if (I == E) { 144 // No more characters left? 145 H.HandleIncompleteFormatSpecifier(Start, E); 146 return true; 147 } 148 149 // Look for the precision (if any). 150 if (*I == '.') { 151 const char *startPrecision = I++; 152 if (I == E) { 153 H.HandleIncompletePrecision(I - 1); 154 return true; 155 } 156 157 FS.setPrecision(ParseAmount(I, E)); 158 159 if (I == E) { 160 // No more characters left? 161 H.HandleIncompletePrecision(startPrecision); 162 return true; 163 } 164 } 165 166 // Look for the length modifier. 167 LengthModifier lm = None; 168 switch (*I) { 169 default: 170 break; 171 case 'h': 172 ++I; 173 lm = (I != E && *I == 'h') ? ++I, AsChar : AsShort; 174 break; 175 case 'l': 176 ++I; 177 lm = (I != E && *I == 'l') ? ++I, AsLongLong : AsLong; 178 break; 179 case 'j': lm = AsIntMax; ++I; break; 180 case 'z': lm = AsSizeT; ++I; break; 181 case 't': lm = AsPtrDiff; ++I; break; 182 case 'L': lm = AsLongDouble; ++I; break; 183 } 184 FS.setLengthModifier(lm); 185 186 if (I == E) { 187 // No more characters left? 188 H.HandleIncompleteFormatSpecifier(Start, E); 189 return true; 190 } 191 192 // Finally, look for the conversion specifier. 193 const char *conversionPosition = I++; 194 ConversionSpecifier::Kind k; 195 switch (*conversionPosition) { 196 default: 197 H.HandleInvalidConversionSpecifier(conversionPosition); 198 return true; 199 // C99: 7.19.6.1 (section 8). 200 case 'd': k = ConversionSpecifier::dArg; break; 201 case 'i': k = ConversionSpecifier::iArg; break; 202 case 'o': k = ConversionSpecifier::oArg; break; 203 case 'u': k = ConversionSpecifier::uArg; break; 204 case 'x': k = ConversionSpecifier::xArg; break; 205 case 'X': k = ConversionSpecifier::XArg; break; 206 case 'f': k = ConversionSpecifier::fArg; break; 207 case 'F': k = ConversionSpecifier::FArg; break; 208 case 'e': k = ConversionSpecifier::eArg; break; 209 case 'E': k = ConversionSpecifier::EArg; break; 210 case 'g': k = ConversionSpecifier::gArg; break; 211 case 'G': k = ConversionSpecifier::GArg; break; 212 case 'a': k = ConversionSpecifier::aArg; break; 213 case 'A': k = ConversionSpecifier::AArg; break; 214 case 'c': k = ConversionSpecifier::IntAsCharArg; break; 215 case 's': k = ConversionSpecifier::CStrArg; break; 216 case 'p': k = ConversionSpecifier::VoidPtrArg; break; 217 case 'n': k = ConversionSpecifier::OutIntPtrArg; break; 218 case '%': k = ConversionSpecifier::PercentArg; break; 219 // Objective-C. 220 case '@': k = ConversionSpecifier::ObjCObjArg; break; 221 } 222 FS.setConversionSpecifier(ConversionSpecifier(conversionPosition, k)); 223 return FormatSpecifierResult(Start, FS); 224} 225 226namespace clang { namespace analyze_printf { 227bool ParseFormatString(FormatStringHandler &H, 228 const char *I, const char *E) { 229 // Keep looking for a format specifier until we have exhausted the string. 230 while (I != E) { 231 const FormatSpecifierResult &FSR = ParseFormatSpecifier(H, I, E); 232 // Did an error of any kind occur when parsing the specifier? If so, 233 // don't do any more processing. 234 if (FSR.hasError()) 235 return true;; 236 // Done processing the string? 237 if (!FSR.hasValue()) 238 break; 239 // We have a format specifier. Pass it to the callback. 240 if (!H.HandleFormatSpecifier(FSR.getValue(), FSR.getStart(), 241 I - FSR.getStart())) 242 return false; 243 } 244 assert(I == E && "Format string not exhausted"); 245 return false; 246} 247}} 248 249FormatStringHandler::~FormatStringHandler() {} 250