This patch adds support for the FreeBSD-specific -fformat-extension option,
which enables additional printf modifiers for the kernel.

Introduced here: http://svnweb.freebsd.org/changeset/base/208987

Index: tools/clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- tools/clang/lib/Frontend/CompilerInvocation.cpp
+++ tools/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1319,6 +1319,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgLi
   Opts.ShortWChar = Args.hasArg(OPT_fshort_wchar);
   Opts.ShortEnums = Args.hasArg(OPT_fshort_enums);
   Opts.Freestanding = Args.hasArg(OPT_ffreestanding);
+  Opts.FormatExtensions = Args.hasArg(OPT_fformat_extensions);
   Opts.NoBuiltin = Args.hasArg(OPT_fno_builtin) || Opts.Freestanding;
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
Index: tools/clang/lib/Analysis/FormatString.cpp
===================================================================
--- tools/clang/lib/Analysis/FormatString.cpp
+++ tools/clang/lib/Analysis/FormatString.cpp
@@ -548,6 +548,11 @@ const char *ConversionSpecifier::toString() const
   // Objective-C specific specifiers.
   case ObjCObjArg: return "@";
 
+  // FreeBSD specific specifiers.
+  case FreeBSDbArg: return "b";
+  case FreeBSDDArg: return "D";
+  case FreeBSDrArg: return "r";
+
   // GlibC specific specifiers.
   case PrintErrno: return "m";
   }
@@ -626,6 +631,7 @@ bool FormatSpecifier::hasValidLengthModifier(const
         case ConversionSpecifier::xArg:
         case ConversionSpecifier::XArg:
         case ConversionSpecifier::nArg:
+        case ConversionSpecifier::FreeBSDrArg:
           return true;
         default:
           return false;
@@ -654,6 +660,7 @@ bool FormatSpecifier::hasValidLengthModifier(const
         case ConversionSpecifier::nArg:
         case ConversionSpecifier::cArg:
         case ConversionSpecifier::sArg:
+        case ConversionSpecifier::FreeBSDrArg:
         case ConversionSpecifier::ScanListArg:
           return true;
         default:
@@ -774,6 +781,9 @@ bool FormatSpecifier::hasStandardConversionSpecifi
     case ConversionSpecifier::SArg:
       return LangOpt.ObjC1 || LangOpt.ObjC2;
     case ConversionSpecifier::InvalidSpecifier:
+    case ConversionSpecifier::FreeBSDbArg:
+    case ConversionSpecifier::FreeBSDDArg:
+    case ConversionSpecifier::FreeBSDrArg:
     case ConversionSpecifier::PrintErrno:
     case ConversionSpecifier::DArg:
     case ConversionSpecifier::OArg:
Index: tools/clang/lib/Analysis/PrintfFormatString.cpp
===================================================================
--- tools/clang/lib/Analysis/PrintfFormatString.cpp
+++ tools/clang/lib/Analysis/PrintfFormatString.cpp
@@ -198,10 +198,25 @@ static PrintfSpecifierResult ParsePrintfSpecifier(
     case '@': k = ConversionSpecifier::ObjCObjArg; break;
     // Glibc specific.
     case 'm': k = ConversionSpecifier::PrintErrno; break;
+    // FreeBSD format extensions
+    case 'b':
+      if (LO.FormatExtensions)
+        k = ConversionSpecifier::FreeBSDbArg; // int followed by char *
+      break;
+    case 'r':
+      if (LO.FormatExtensions)
+        k = ConversionSpecifier::FreeBSDrArg;
+      break;
+    case 'y':
+      if (LO.FormatExtensions)
+        k = ConversionSpecifier::iArg;
+      break;
     // Apple-specific
     case 'D':
       if (Target.getTriple().isOSDarwin())
         k = ConversionSpecifier::DArg;
+      else if (LO.FormatExtensions)
+        k = ConversionSpecifier::FreeBSDDArg; // u_char * followed by char *
       break;
     case 'O':
       if (Target.getTriple().isOSDarwin())
@@ -216,6 +231,10 @@ static PrintfSpecifierResult ParsePrintfSpecifier(
   FS.setConversionSpecifier(CS);
   if (CS.consumesDataArgument() && !FS.usesPositionalArg())
     FS.setArgIndex(argIndex++);
+  // FreeBSD extension
+  if (k == ConversionSpecifier::FreeBSDbArg ||
+      k == ConversionSpecifier::FreeBSDDArg)
+    argIndex++;
 
   if (k == ConversionSpecifier::InvalidSpecifier) {
     // Assume the conversion takes one argument.
@@ -618,6 +637,7 @@ bool PrintfSpecifier::hasValidPlusPrefix() const {
   case ConversionSpecifier::GArg:
   case ConversionSpecifier::aArg:
   case ConversionSpecifier::AArg:
+  case ConversionSpecifier::FreeBSDrArg:
     return true;
 
   default:
@@ -643,6 +663,7 @@ bool PrintfSpecifier::hasValidAlternativeForm() co
   case ConversionSpecifier::FArg:
   case ConversionSpecifier::gArg:
   case ConversionSpecifier::GArg:
+  case ConversionSpecifier::FreeBSDrArg:
     return true;
 
   default:
Index: tools/clang/lib/Sema/SemaChecking.cpp
===================================================================
--- tools/clang/lib/Sema/SemaChecking.cpp
+++ tools/clang/lib/Sema/SemaChecking.cpp
@@ -2980,6 +2980,42 @@ CheckPrintfHandler::HandlePrintfSpecifier(const an
     CoveredArgs.set(argIndex);
   }
 
+  // FreeBSD kernel extensions.
+  if (CS.getKind() == ConversionSpecifier::FreeBSDbArg ||
+      CS.getKind() == ConversionSpecifier::FreeBSDDArg) { 
+    // We need at least two arguments.
+    if (!CheckNumArgs(FS, CS, startSpecifier, specifierLen, argIndex + 1))
+      return false;
+
+    // Claim the second argument.
+    CoveredArgs.set(argIndex + 1);
+
+    // Type check the first argument (int for %b, pointer for %D)
+    const Expr *Ex = getDataArg(argIndex);
+    const analyze_printf::ArgType &AT =
+      (CS.getKind() == ConversionSpecifier::FreeBSDbArg) ?
+        ArgType(S.Context.IntTy) : ArgType::CPointerTy;
+    if (AT.isValid() && !AT.matchesType(S.Context, Ex->getType()))
+      S.Diag(getLocationOfByte(CS.getStart()),
+             diag::warn_printf_conversion_argument_type_mismatch)
+        << AT.getRepresentativeType(S.Context) << Ex->getType()
+        << getSpecifierRange(startSpecifier, specifierLen)
+        << Ex->getSourceRange();
+
+    // Type check the second argument (char * for both %b and %D)
+    Ex = getDataArg(argIndex + 1);
+    const analyze_printf::ArgType &AT2 = ArgType::CStrTy;
+    if (AT2.isValid() && !AT2.matchesType(S.Context, Ex->getType()))
+      S.Diag(getLocationOfByte(CS.getStart()),
+             diag::warn_printf_conversion_argument_type_mismatch)
+        << AT2.getRepresentativeType(S.Context) << Ex->getType()
+        << getSpecifierRange(startSpecifier, specifierLen)
+        << Ex->getSourceRange();
+
+     return true;
+  }
+  // END OF FREEBSD EXTENSIONS
+
   // Check for using an Objective-C specific conversion specifier
   // in a non-ObjC literal.
   if (!ObjCContext && CS.isObjCArg()) {
Index: tools/clang/lib/Driver/Tools.cpp
===================================================================
--- tools/clang/lib/Driver/Tools.cpp
+++ tools/clang/lib/Driver/Tools.cpp
@@ -2984,6 +2984,7 @@ void Clang::ConstructJob(Compilation &C, const Job
 
   // Forward -f (flag) options which we can pass directly.
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
+  Args.AddLastArg(CmdArgs, options::OPT_fformat_extensions);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
   Args.AddLastArg(CmdArgs, options::OPT_flimit_debug_info);
   Args.AddLastArg(CmdArgs, options::OPT_fno_limit_debug_info);
Index: tools/clang/include/clang/Basic/LangOptions.def
===================================================================
--- tools/clang/include/clang/Basic/LangOptions.def
+++ tools/clang/include/clang/Basic/LangOptions.def
@@ -84,6 +84,7 @@ LANGOPT(TraditionalCPP    , 1, 0, "traditional CPP
 LANGOPT(RTTI              , 1, 1, "run-time type information")
 LANGOPT(MSBitfields       , 1, 0, "Microsoft-compatible structure layout")
 LANGOPT(Freestanding, 1, 0, "freestanding implementation")
+LANGOPT(FormatExtensions  , 1, 0, "FreeBSD format extensions")
 LANGOPT(NoBuiltin         , 1, 0, "disable builtin functions")
 LANGOPT(NoMathBuiltin     , 1, 0, "disable math builtin functions")
 
Index: tools/clang/include/clang/Analysis/Analyses/FormatString.h
===================================================================
--- tools/clang/include/clang/Analysis/Analyses/FormatString.h
+++ tools/clang/include/clang/Analysis/Analyses/FormatString.h
@@ -158,6 +158,11 @@ class ConversionSpecifier {
     ObjCObjArg,  // '@'
     ObjCBeg = ObjCObjArg, ObjCEnd = ObjCObjArg,
 
+    // FreeBSD specific specifiers
+    FreeBSDbArg,
+    FreeBSDDArg,
+    FreeBSDrArg,
+
     // GlibC specific specifiers.
     PrintErrno,   // 'm'
 
Index: tools/clang/include/clang/Driver/Options.td
===================================================================
--- tools/clang/include/clang/Driver/Options.td
+++ tools/clang/include/clang/Driver/Options.td
@@ -530,6 +530,8 @@ def fno_rewrite_includes : Flag<["-"], "fno-rewrit
 
 def ffreestanding : Flag<["-"], "ffreestanding">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Assert that the compilation takes place in a freestanding environment">;
+def fformat_extensions: Flag<["-"], "fformat-extensions">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Enable FreeBSD kernel specific format string extensions">;
 def fgnu_keywords : Flag<["-"], "fgnu-keywords">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Allow GNU-extension keywords regardless of language standard">;
 def fgnu89_inline : Flag<["-"], "fgnu89-inline">, Group<f_Group>, Flags<[CC1Option]>,