Debug.cpp revision 206083 
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 handle 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 in release mode, the -debug-* options and all code in DEBUG()
22// statements disappears, so it does not effect the runtime of the code.
23//
24//===----------------------------------------------------------------------===//
25
26#include "llvm/Support/CommandLine.h"
27#include "llvm/Support/Debug.h"
28#include "llvm/Support/circular_raw_ostream.h"
29#include "llvm/System/Signals.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;
54static struct DebugOnlyOpt {
55  void operator=(const std::string &Val) const {
56    DebugFlag |= !Val.empty();
57    CurrentDebugType = Val;
58  }
59} DebugOnlyOptLoc;
60
61static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
62DebugOnly("debug-only", cl::desc("Enable a specific type of debug output"),
63          cl::Hidden, cl::value_desc("debug string"),
64          cl::location(DebugOnlyOptLoc), cl::ValueRequired);
65
66// Signal handlers - dump debug output on termination.
67static void debug_user_sig_handler(void *Cookie) {
68  // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
69  // know that debug mode is enabled and dbgs() really is a
70  // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
71  // errs() but this will never be invoked.
72  llvm::circular_raw_ostream *dbgout =
73    static_cast<llvm::circular_raw_ostream *>(&llvm::dbgs());
74  dbgout->flushBufferWithBanner();
75}
76
77// isCurrentDebugType - Return true if the specified string is the debug type
78// specified on the command line, or if none was specified on the command line
79// with the -debug-only=X option.
80//
81bool llvm::isCurrentDebugType(const char *DebugType) {
82  return CurrentDebugType.empty() || DebugType == CurrentDebugType;
83}
84
85/// SetCurrentDebugType - Set the current debug type, as if the -debug-only=X
86/// option were specified.  Note that DebugFlag also needs to be set to true for
87/// debug output to be produced.
88///
89void llvm::SetCurrentDebugType(const char *Type) {
90  CurrentDebugType = Type;
91}
92
93/// dbgs - Return a circular-buffered debug stream.
94raw_ostream &llvm::dbgs() {
95  // Do one-time initialization in a thread-safe way.
96  static struct dbgstream {
97    circular_raw_ostream strm;
98
99    dbgstream() :
100        strm(errs(), "*** Debug Log Output ***\n",
101             (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
102      if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
103        // TODO: Add a handler for SIGUSER1-type signals so the user can
104        // force a debug dump.
105        sys::AddSignalHandler(&debug_user_sig_handler, 0);
106      // Otherwise we've already set the debug stream buffer size to
107      // zero, disabling buffering so it will output directly to errs().
108    }
109  } thestrm;
110
111  return thestrm.strm;
112}
113
114#else
115// Avoid "has no symbols" warning.
116namespace llvm {
117  /// dbgs - Return errs().
118  raw_ostream &dbgs() {
119    return errs();
120  }
121}
122
123#endif
124
125/// EnableDebugBuffering - Turn on signal handler installation.
126///
127bool llvm::EnableDebugBuffering = false;
128