Add skeleton for a more structured way to analyzing pring format

strings than what we currently have in Sema.  This is both an
experiment and a WIP.

The idea is simple: parse the format string incrementally,
constructing a well-structure representation of each format specifier.
Each format specifier is then handed back one-by-one to a client via a
callback.  Malformed format strings are also handled with callbacks.
The idea is to separate the parsing of the format string from the
emission of diagnostics.  Currently what we have in Sema for handling
format strings is a mongrel of both that is hard to follow and
difficult to modify (I can apply this label since I'm the original
author of that code).

This is in libAnalysis as it is reasonable generic and can potentially
be used both by libSema and libChecker.

Comments welcome.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94702 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 239 insertions, 0 deletions

diff --git a/lib/Analysis/PrintfFormatString.cpp b/lib/Analysis/PrintfFormatString.cpp
new file mode 100644
index 0000000000..b2adeeb5f9
--- /dev/null
+++ b/lib/Analysis/PrintfFormatString.cpp
@@ -0,0 +1,239 @@
+//= PrintfFormatStrings.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 printf and friends.  The structure of format
+// strings for fprintf() are described in C99 7.19.6.1.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/PrintfFormatString.h"
+
+using namespace clang;
+using namespace printf;
+
+namespace {
+class FormatSpecifierResult {
+  FormatSpecifier FS;
+  const char *Start;
+  bool HasError;
+public:
+  FormatSpecifierResult(bool err = false)
+    : Start(0), HasError(err) {}
+  FormatSpecifierResult(const char *start,
+                        const printf::FormatSpecifier &fs)
+    : FS(fs), Start(start), HasError(false) {}
+
+  
+  const char *getStart() const { return Start; }
+  bool hasError() const { return HasError; }
+  bool hasValue() const { return Start != 0; }
+  const FormatSpecifier &getValue() const {
+    assert(hasValue());
+    return FS;
+  }
+  const printf::FormatSpecifier &getValue() { return FS; }
+};
+} // end anonymous namespace
+
+template <typename T>
+class UpdateOnReturn {
+  T &ValueToUpdate;
+  const T &ValueToCopy;
+public:
+  UpdateOnReturn(T &valueToUpdate, const T &valueToCopy)
+    : ValueToUpdate(valueToUpdate), ValueToCopy(valueToCopy) {}
+  
+  ~UpdateOnReturn() {
+    ValueToUpdate = ValueToCopy;
+  }
+};  
+
+static OptionalAmount ParseAmount(const char *&Beg, const char *E) {
+  const char *I = Beg;
+  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
+  
+  bool foundDigits = false;
+  unsigned accumulator = 0;
+
+  for ( ; I != E; ++I) {
+    char c = *I;
+    if (c >= '0' && c <= '9') {
+      foundDigits = true;
+      accumulator += (accumulator * 10) + (c - '0');
+      continue;
+    }
+
+    if (foundDigits)
+      return OptionalAmount(accumulator);
+    
+    if (c == '*')
+      return OptionalAmount(OptionalAmount::Arg);
+    
+    break;
+  }
+  
+  return OptionalAmount();  
+}
+
+static FormatSpecifierResult ParseFormatSpecifier(printf::FormatStringHandler &H,
+                                                  const char *&Beg, const char *E) {
+  
+  const char *I = Beg;
+  const char *Start = NULL;
+  UpdateOnReturn <const char*> UpdateBeg(Beg, I);
+
+  // Look for a '%' character that indicates the start of a format specifier.
+  while (I != E) {
+    char c = *I;
+    ++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.HandleIncompleteFormatSpecifier(Start, E);
+    return true;
+  }
+      
+  FormatSpecifier FS;
+  
+  // Look for flags (if any).
+  bool hasMore = true;
+  for ( ; I != E; ++I) {
+    switch (*I) {
+      default: hasMore = false; break;
+      case '-': FS.setIsLeftJustified(); break;
+      case '+': FS.setHasPlusPrefix(); break;
+      case ' ': FS.setHasSpacePrefix(); break;
+      case '#': FS.setHasAlternativeForm(); break;
+      case '0': FS.setHasLeadingZeros(); break;
+    }
+    if (!hasMore)
+      break;
+  }      
+
+  if (I == E) {
+    // No more characters left?
+    H.HandleIncompleteFormatSpecifier(Start, E);
+    return true;
+  }
+  
+  // Look for the field width (if any).
+  FS.setFieldWidth(ParseAmount(I, E));
+      
+  if (I == E) {
+    // No more characters left?
+    H.HandleIncompleteFormatSpecifier(Start, E);
+    return true;
+  }  
+  
+  // Look for the precision (if any).  
+  if (*I == '.') {
+    const char *startPrecision = I++;
+    if (I == E) {
+      H.HandleIncompletePrecision(I - 1);
+      return true;
+    }
+    
+    FS.setPrecision(ParseAmount(I, E));
+
+    if (I == E) {
+      // No more characters left?
+      H.HandleIncompletePrecision(startPrecision);
+      return true;
+    }
+  }
+
+  // Look for the length modifier.
+  LengthModifier lm = None;
+  switch (*I) {
+    default:
+      break;
+    case 'h':
+      ++I;
+      lm = (I != E && *I == 'h') ? ++I, AsChar : AsShort;      
+      break;
+    case 'l':
+      ++I;
+      lm = (I != E && *I == 'l') ? ++I, AsLongLong : AsLong;
+      break;
+    case 'j': lm = AsIntMax;     ++I; break;
+    case 'z': lm = AsSizeT;      ++I; break;
+    case 't': lm = AsPtrDiff;    ++I; break;
+    case 'L': lm = AsLongDouble; ++I; break;
+  }
+  FS.setLengthModifier(lm);
+  
+  if (I == E) {
+    // No more characters left?
+    H.HandleIncompleteFormatSpecifier(Start, E);
+    return true;
+  }
+  
+  // Finally, look for the conversion specifier.
+  ConversionSpecifier::Kind cs;
+  switch (*I) {
+    default:
+      H.HandleInvalidConversionSpecifier(I);
+      return true;
+    case 'd' : cs = ConversionSpecifier::dArg; break;
+    case 'i' : cs = ConversionSpecifier::iArg; break;
+    case 'o' : cs = ConversionSpecifier::oArg; break;
+    case 'u' : cs = ConversionSpecifier::uArg; break;
+    case 'x' : cs = ConversionSpecifier::xArg; break;
+    case 'X' : cs = ConversionSpecifier::XArg; break;
+    case 'f' : cs = ConversionSpecifier::fArg; break;
+    case 'F' : cs = ConversionSpecifier::FArg; break;
+    case 'e' : cs = ConversionSpecifier::eArg; break;
+    case 'E' : cs = ConversionSpecifier::EArg; break;
+    case 'g' : cs = ConversionSpecifier::gArg; break;
+    case 'G' : cs = ConversionSpecifier::GArg; break;
+    case 'a' : cs = ConversionSpecifier::aArg; break;
+    case 'A' : cs = ConversionSpecifier::AArg; break;
+    case 'c' : cs = ConversionSpecifier::IntAsCharArg; break;
+    case 's' : cs = ConversionSpecifier::CStrArg;      break;
+    case 'p' : cs = ConversionSpecifier::VoidPtrArg;   break;
+    case 'n' : cs = ConversionSpecifier::OutIntPtrArg; break;
+    case '%' : cs = ConversionSpecifier::PercentArg;   break;
+  }
+  FS.setConversionSpecifier(cs);
+  return FormatSpecifierResult(Start, FS);
+}
+
+bool ParseFormatSring(FormatStringHandler &H, const char *I, const char *E) {
+  // Keep looking for a format specifier until we have exhausted the string.
+  while (I != E) {
+    const FormatSpecifierResult &FSR = ParseFormatSpecifier(H, I, E);
+    // Did an error of any kind occur when parsing the specifier?  If so,
+    // don't do any more processing.
+    if (FSR.hasError())
+      return true;;
+    // Done processing the string?
+    if (!FSR.hasValue())
+      break;    
+    // We have a format specifier.  Pass it to the callback.
+    H.HandleFormatSpecifier(FSR.getValue(), FSR.getStart(), I);
+  }  
+  assert(I == E && "Format string not exhausted");      
+  return false;
+}
+
+FormatStringHandler::~FormatStringHandler() {}