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#include "llvm/Support/raw_ostream.h"
32
33#undef isCurrentDebugType
34#undef setCurrentDebugType
35
36using namespace llvm;
37
38// Even though LLVM might be built with NDEBUG, define symbols that the code
39// built without NDEBUG can depend on via the llvm/Support/Debug.h header.
40namespace llvm {
41/// Exported boolean set by the -debug option.
42bool DebugFlag = false;
43
44static ManagedStatic<std::vector<std::string>> CurrentDebugType;
45
46/// Return true if the specified string is the debug type
47/// specified on the command line, or if none was specified on the command line
48/// with the -debug-only=X option.
49bool isCurrentDebugType(const char *DebugType) {
50  if (CurrentDebugType->empty())
51    return true;
52  // See if DebugType is in list. Note: do not use find() as that forces us to
53  // unnecessarily create an std::string instance.
54  for (auto &d : *CurrentDebugType) {
55    if (d == DebugType)
56      return true;
57  }
58  return false;
59}
60
61/// Set the current debug type, as if the -debug-only=X
62/// option were specified.  Note that DebugFlag also needs to be set to true for
63/// debug output to be produced.
64///
65void setCurrentDebugType(const char *Type) {
66  CurrentDebugType->clear();
67  CurrentDebugType->push_back(Type);
68}
69
70} // namespace llvm
71
72// All Debug.h functionality is a no-op in NDEBUG mode.
73#ifndef NDEBUG
74
75// -debug - Command line option to enable the DEBUG statements in the passes.
76// This flag may only be enabled in debug builds.
77static cl::opt<bool, true>
78Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
79      cl::location(DebugFlag));
80
81// -debug-buffer-size - Buffer the last N characters of debug output
82//until program termination.
83static cl::opt<unsigned>
84DebugBufferSize("debug-buffer-size",
85                cl::desc("Buffer the last N characters of debug output "
86                         "until program termination. "
87                         "[default 0 -- immediate print-out]"),
88                cl::Hidden,
89                cl::init(0));
90
91namespace {
92
93struct DebugOnlyOpt {
94  void operator=(const std::string &Val) const {
95    if (Val.empty())
96      return;
97    DebugFlag = true;
98    CurrentDebugType->push_back(Val);
99  }
100};
101
102}
103
104static DebugOnlyOpt DebugOnlyOptLoc;
105
106static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
107DebugOnly("debug-only", cl::desc("Enable a specific type of debug output"),
108          cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
109          cl::location(DebugOnlyOptLoc), cl::ValueRequired);
110
111// Signal handlers - dump debug output on termination.
112static void debug_user_sig_handler(void *Cookie) {
113  // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
114  // know that debug mode is enabled and dbgs() really is a
115  // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
116  // errs() but this will never be invoked.
117  llvm::circular_raw_ostream &dbgout =
118      static_cast<circular_raw_ostream &>(llvm::dbgs());
119  dbgout.flushBufferWithBanner();
120}
121
122/// dbgs - Return a circular-buffered debug stream.
123raw_ostream &llvm::dbgs() {
124  // Do one-time initialization in a thread-safe way.
125  static struct dbgstream {
126    circular_raw_ostream strm;
127
128    dbgstream() :
129        strm(errs(), "*** Debug Log Output ***\n",
130             (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
131      if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
132        // TODO: Add a handler for SIGUSER1-type signals so the user can
133        // force a debug dump.
134        sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
135      // Otherwise we've already set the debug stream buffer size to
136      // zero, disabling buffering so it will output directly to errs().
137    }
138  } thestrm;
139
140  return thestrm.strm;
141}
142
143#else
144// Avoid "has no symbols" warning.
145namespace llvm {
146  /// dbgs - Return errs().
147  raw_ostream &dbgs() {
148    return errs();
149  }
150}
151
152#endif
153
154/// EnableDebugBuffering - Turn on signal handler installation.
155///
156bool llvm::EnableDebugBuffering = false;
157