src/llvm/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 handy 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 without assertions, the -debug-* options and all code in
  22 // DEBUG() statements disappears, so it does not affect the runtime of the code.
  23 //
  24 //===----------------------------------------------------------------------===//
  25
  26 #include "llvm/Support/Debug.h"
  27 #include "llvm/Support/CommandLine.h"
  28 #include "llvm/Support/ManagedStatic.h"
  29 #include "llvm/Support/Signals.h"
  30 #include "llvm/Support/circular_raw_ostream.h"
  31
  32 using namespace llvm;
  33
  34 // All Debug.h functionality is a no-op in NDEBUG mode.
  35 #ifndef NDEBUG
  36 bool llvm::DebugFlag;  // DebugFlag - Exported boolean set by the -debug option
  37
  38 // -debug - Command line option to enable the DEBUG statements in the passes.
  39 // This flag may only be enabled in debug builds.
  40 static cl::opt<bool, true>
  41 Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
  42       cl::location(DebugFlag));
  43
  44 // -debug-buffer-size - Buffer the last N characters of debug output
  45 //until program termination.
  46 static cl::opt<unsigned>
  47 DebugBufferSize("debug-buffer-size",
  48                 cl::desc("Buffer the last N characters of debug output "
  49                          "until program termination. "
  50                          "[default 0 -- immediate print-out]"),
  51                 cl::Hidden,
  52                 cl::init(0));
  53
  54 static ManagedStatic<std::vector<std::string> > CurrentDebugType;
  55
  56 namespace {
  57
  58 struct DebugOnlyOpt {
  59   void operator=(const std::string &Val) const {
  60     if (Val.empty())
  61       return;
  62     DebugFlag = true;
  63     CurrentDebugType->push_back(Val);
  64   }
  65 };
  66
  67 }
  68
  69 static DebugOnlyOpt DebugOnlyOptLoc;
  70
  71 static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
  72 DebugOnly("debug-only", cl::desc("Enable a specific type of debug output"),
  73           cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
  74           cl::location(DebugOnlyOptLoc), cl::ValueRequired);
  75
  76 // Signal handlers - dump debug output on termination.
  77 static void debug_user_sig_handler(void *Cookie) {
  78   // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
  79   // know that debug mode is enabled and dbgs() really is a
  80   // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
  81   // errs() but this will never be invoked.
  82   llvm::circular_raw_ostream *dbgout =
  83     static_cast<llvm::circular_raw_ostream *>(&llvm::dbgs());
  84   dbgout->flushBufferWithBanner();
  85 }
  86
  87 // isCurrentDebugType - Return true if the specified string is the debug type
  88 // specified on the command line, or if none was specified on the command line
  89 // with the -debug-only=X option.
  90 //
  91 bool llvm::isCurrentDebugType(const char *DebugType) {
  92   if (CurrentDebugType->empty())
  93     return true;
  94   // see if DebugType is in list. Note: do not use find() as that forces us to
  95   // unnecessarily create an std::string instance.
  96   for (auto d : *CurrentDebugType) {
  97     if (d == DebugType)
  98       return true;
  99   }
 100   return false;
 101 }
 102
 103 /// setCurrentDebugType - Set the current debug type, as if the -debug-only=X
 104 /// option were specified.  Note that DebugFlag also needs to be set to true for
 105 /// debug output to be produced.
 106 ///
 107 void llvm::setCurrentDebugType(const char *Type) {
 108   CurrentDebugType->clear();
 109   CurrentDebugType->push_back(Type);
 110 }
 111
 112 /// dbgs - Return a circular-buffered debug stream.
 113 raw_ostream &llvm::dbgs() {
 114   // Do one-time initialization in a thread-safe way.
 115   static struct dbgstream {
 116     circular_raw_ostream strm;
 117
 118     dbgstream() :
 119         strm(errs(), "*** Debug Log Output ***\n",
 120              (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
 121       if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
 122         // TODO: Add a handler for SIGUSER1-type signals so the user can
 123         // force a debug dump.
 124         sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
 125       // Otherwise we've already set the debug stream buffer size to
 126       // zero, disabling buffering so it will output directly to errs().
 127     }
 128   } thestrm;
 129
 130   return thestrm.strm;
 131 }
 132
 133 #else
 134 // Avoid "has no symbols" warning.
 135 namespace llvm {
 136   /// dbgs - Return errs().
 137   raw_ostream &dbgs() {
 138     return errs();
 139   }
 140 }
 141
 142 #endif
 143
 144 /// EnableDebugBuffering - Turn on signal handler installation.
 145 ///
 146 bool llvm::EnableDebugBuffering = false;