llvm-project/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 handle 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 in release mode, the -debug-* options and all code in DEBUG()
// statements disappears, so it does not effect the runtime of the code.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;

bool llvm::DebugFlag;  // DebugFlag - Exported boolean set by the -debug option

namespace {
#ifndef NDEBUG
  // -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));

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

// 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) {
#ifndef NDEBUG
  return CurrentDebugType.empty() || DebugType == CurrentDebugType;
#else
  return false;
#endif
}

/// getNullOutputStream - Return a null string that does not output
/// anything.  This hides the static variable from other modules.
///
OStream &llvm::getNullOutputStream() {
  static llvm::OStream NullStream(0);
  return NullStream;
}

// getErrorOutputStream - Returns the error output stream (std::cerr). This
// places the std::c* I/O streams into one .cpp file and relieves the whole
// program from having to have hundreds of static c'tor/d'tors for them.
// 
OStream &llvm::getErrorOutputStream(const char *DebugType) {
  static OStream cnoout(0);
  if (DebugFlag && isCurrentDebugType(DebugType))
    return cerr;
  else
    return cnoout;
}