lib/Support/Debug.cpp

   1 //===-- Debug.cpp - An easy way to add debug output to your code ----------===//
   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 // This file implements a handle way of adding debugging information to your
  11 // code, without it being enabled all of the time, and without having to add
  12 // command line options to enable it.
  13 //
  14 // In particular, just wrap your code with the DEBUG() macro, and it will be
  15 // enabled automatically if you specify '-debug' on the command-line.
  16 // Alternatively, you can also use the SET_DEBUG_TYPE("foo") macro to specify
  17 // that your debug code belongs to class "foo".  Then, on the command line, you
  18 // can specify '-debug-only=foo' to enable JUST the debug information for the
  19 // foo class.
  20 //
  21 // When compiling in release mode, the -debug-* options and all code in DEBUG()
  22 // statements disappears, so it does not effect the runtime of the code.
  23 //
  24 //===----------------------------------------------------------------------===//
  25
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/Debug.h"
  28 #include "llvm/Support/circular_raw_ostream.h"
  29 #include "llvm/Support/Signals.h"
  30
  31 using namespace llvm;
  32
  33 // All Debug.h functionality is a no-op in NDEBUG mode.
  34 #ifndef NDEBUG
  35 bool llvm::DebugFlag;  // DebugFlag - Exported boolean set by the -debug option
  36
  37 // -debug - Command line option to enable the DEBUG statements in the passes.
  38 // This flag may only be enabled in debug builds.
  39 static cl::opt<bool, true>
  40 Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
  41       cl::location(DebugFlag));
  42
  43 // -debug-buffer-size - Buffer the last N characters of debug output
  44 //until program termination.
  45 static cl::opt<unsigned>
  46 DebugBufferSize("debug-buffer-size",
  47                 cl::desc("Buffer the last N characters of debug output"
  48                          "until program termination. "
  49                          "[default 0 -- immediate print-out]"),
  50                 cl::Hidden,
  51                 cl::init(0));
  52
  53 static std::string CurrentDebugType;
  54
  55 namespace {
  56
  57 struct DebugOnlyOpt {
  58   void operator=(const std::string &Val) const {
  59     DebugFlag |= !Val.empty();
  60     CurrentDebugType = Val;
  61   }
  62 };
  63
  64 }
  65
  66 static DebugOnlyOpt DebugOnlyOptLoc;
  67
  68 static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
  69 DebugOnly("debug-only", cl::desc("Enable a specific type of debug output"),
  70           cl::Hidden, cl::value_desc("debug string"),
  71           cl::location(DebugOnlyOptLoc), cl::ValueRequired);
  72
  73 // Signal handlers - dump debug output on termination.
  74 static void debug_user_sig_handler(void *Cookie) {
  75   // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
  76   // know that debug mode is enabled and dbgs() really is a
  77   // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
  78   // errs() but this will never be invoked.
  79   llvm::circular_raw_ostream *dbgout =
  80     static_cast<llvm::circular_raw_ostream *>(&llvm::dbgs());
  81   dbgout->flushBufferWithBanner();
  82 }
  83
  84 // isCurrentDebugType - Return true if the specified string is the debug type
  85 // specified on the command line, or if none was specified on the command line
  86 // with the -debug-only=X option.
  87 //
  88 bool llvm::isCurrentDebugType(const char *DebugType) {
  89   return CurrentDebugType.empty() || DebugType == CurrentDebugType;
  90 }
  91
  92 /// SetCurrentDebugType - Set the current debug type, as if the -debug-only=X
  93 /// option were specified.  Note that DebugFlag also needs to be set to true for
  94 /// debug output to be produced.
  95 ///
  96 void llvm::SetCurrentDebugType(const char *Type) {
  97   CurrentDebugType = Type;
  98 }
  99
 100 /// dbgs - Return a circular-buffered debug stream.
 101 raw_ostream &llvm::dbgs() {
 102   // Do one-time initialization in a thread-safe way.
 103   static struct dbgstream {
 104     circular_raw_ostream strm;
 105
 106     dbgstream() :
 107         strm(errs(), "*** Debug Log Output ***\n",
 108              (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
 109       if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
 110         // TODO: Add a handler for SIGUSER1-type signals so the user can
 111         // force a debug dump.
 112         sys::AddSignalHandler(&debug_user_sig_handler, 0);
 113       // Otherwise we've already set the debug stream buffer size to
 114       // zero, disabling buffering so it will output directly to errs().
 115     }
 116   } thestrm;
 117
 118   return thestrm.strm;
 119 }
 120
 121 #else
 122 // Avoid "has no symbols" warning.
 123 namespace llvm {
 124   /// dbgs - Return errs().
 125   raw_ostream &dbgs() {
 126     return errs();
 127   }
 128 }
 129
 130 #endif
 131
 132 /// EnableDebugBuffering - Turn on signal handler installation.
 133 ///
 134 bool llvm::EnableDebugBuffering = false;