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/Signals.h"
29#include "llvm/Support/circular_raw_ostream.h"
30
31using namespace llvm;
32
33// All Debug.h functionality is a no-op in NDEBUG mode.
34#ifndef NDEBUG
35bool 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.
39static cl::opt<bool, true>
40Debug("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.
45static cl::opt<unsigned>
46DebugBufferSize("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
53static std::string CurrentDebugType;
54
55namespace {
56
57struct DebugOnlyOpt {
58  void operator=(const std::string &Val) const {
59    DebugFlag |= !Val.empty();
60    CurrentDebugType = Val;
61  }
62};
63
64}
65
66static DebugOnlyOpt DebugOnlyOptLoc;
67
68static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
69DebugOnly("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.
74static 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//
88bool 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///
96void llvm::setCurrentDebugType(const char *Type) {
97  CurrentDebugType = Type;
98}
99
100/// dbgs - Return a circular-buffered debug stream.
101raw_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, nullptr);
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.
123namespace 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///
134bool llvm::EnableDebugBuffering = false;
135