llvm/lib/Support/Debug.cpp

//===-- Debug.cpp - An easy way to add debug output to your code ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a handy way of adding debugging information to your
// code, without it being enabled all of the time, and without having to add
// command line options to enable it.
//
// In particular, just wrap your code with the DEBUG() macro, and it will be
// enabled automatically if you specify '-debug' on the command-line.
// Alternatively, you can also use the SET_DEBUG_TYPE("foo") macro to specify
// that your debug code belongs to class "foo".  Then, on the command line, you
// can specify '-debug-only=foo' to enable JUST the debug information for the
// foo class.
//
// When compiling without assertions, the -debug-* options and all code in
// DEBUG() statements disappears, so it does not affect the runtime of the code.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/Debug.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/circular_raw_ostream.h"
#include "llvm/Support/ManagedStatic.h"

using namespace llvm;

// All Debug.h functionality is a no-op in NDEBUG mode.
#ifndef NDEBUG
bool llvm::DebugFlag;  // DebugFlag - Exported boolean set by the -debug option

// -debug - Command line option to enable the DEBUG statements in the passes.
// This flag may only be enabled in debug builds.
static cl::opt<bool, true>
Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
      cl::location(DebugFlag));

// -debug-buffer-size - Buffer the last N characters of debug output
//until program termination.
static cl::opt<unsigned>
DebugBufferSize("debug-buffer-size",
                cl::desc("Buffer the last N characters of debug output "
                         "until program termination. "
                         "[default 0 -- immediate print-out]"),
                cl::Hidden,
                cl::init(0));

static ManagedStatic<std::string> CurrentDebugType;

namespace {

struct DebugOnlyOpt {
  void operator=(const std::string &Val) const {
    DebugFlag |= !Val.empty();
    *CurrentDebugType = Val;
  }
};

}

static DebugOnlyOpt DebugOnlyOptLoc;

static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
DebugOnly("debug-only", cl::desc("Enable a specific type of debug output"),
          cl::Hidden, cl::value_desc("debug string"),
          cl::location(DebugOnlyOptLoc), cl::ValueRequired);

// Signal handlers - dump debug output on termination.
static void debug_user_sig_handler(void *Cookie) {
  // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
  // know that debug mode is enabled and dbgs() really is a
  // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
  // errs() but this will never be invoked.
  llvm::circular_raw_ostream *dbgout =
    static_cast<llvm::circular_raw_ostream *>(&llvm::dbgs());
  dbgout->flushBufferWithBanner();
}

// isCurrentDebugType - Return true if the specified string is the debug type
// specified on the command line, or if none was specified on the command line
// with the -debug-only=X option.
//
bool llvm::isCurrentDebugType(const char *DebugType) {
  return CurrentDebugType->empty() || DebugType == *CurrentDebugType;
}

/// setCurrentDebugType - Set the current debug type, as if the -debug-only=X
/// option were specified.  Note that DebugFlag also needs to be set to true for
/// debug output to be produced.
///
void llvm::setCurrentDebugType(const char *Type) {
  *CurrentDebugType = Type;
}

/// dbgs - Return a circular-buffered debug stream.
raw_ostream &llvm::dbgs() {
  // Do one-time initialization in a thread-safe way.
  static struct dbgstream {
    circular_raw_ostream strm;

    dbgstream() :
        strm(errs(), "*** Debug Log Output ***\n",
             (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
      if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
        // TODO: Add a handler for SIGUSER1-type signals so the user can
        // force a debug dump.
        sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
      // Otherwise we've already set the debug stream buffer size to
      // zero, disabling buffering so it will output directly to errs().
    }
  } thestrm;

  return thestrm.strm;
}

#else
// Avoid "has no symbols" warning.
namespace llvm {
  /// dbgs - Return errs().
  raw_ostream &dbgs() {
    return errs();
  }
}

#endif

/// EnableDebugBuffering - Turn on signal handler installation.
///
bool llvm::EnableDebugBuffering = false;