llvm/lib/Support/Debug.cpp

   1 //===-- Debug.cpp - An easy way to add debug output to your code ----------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements a handy way of adding debugging information to your
  10 // code, without it being enabled all of the time, and without having to add
  11 // command line options to enable it.
  12 //
  13 // In particular, just wrap your code with the LLVM_DEBUG() macro, and it will
  14 // be enabled automatically if you specify '-debug' on the command-line.
  15 // Alternatively, you can also use the SET_DEBUG_TYPE("foo") macro to specify
  16 // that your debug code belongs to class "foo".  Then, on the command line, you
  17 // can specify '-debug-only=foo' to enable JUST the debug information for the
  18 // foo class.
  19 //
  20 // When compiling without assertions, the -debug-* options and all code in
  21 // LLVM_DEBUG() statements disappears, so it does not affect the runtime of the
  22 // 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 #include "DebugOptions.h"
  34
  35 #undef isCurrentDebugType
  36 #undef setCurrentDebugType
  37 #undef setCurrentDebugTypes
  38
  39 using namespace llvm;
  40
  41 // Even though LLVM might be built with NDEBUG, define symbols that the code
  42 // built without NDEBUG can depend on via the llvm/Support/Debug.h header.
  43 namespace llvm {
  44 /// Exported boolean set by the -debug option.
  45 bool DebugFlag = false;
  46
  47 static ManagedStatic<std::vector<std::string>> CurrentDebugType;
  48
  49 /// Return true if the specified string is the debug type
  50 /// specified on the command line, or if none was specified on the command line
  51 /// with the -debug-only=X option.
  52 bool isCurrentDebugType(const char *DebugType) {
  53   if (CurrentDebugType->empty())
  54     return true;
  55   // See if DebugType is in list. Note: do not use find() as that forces us to
  56   // unnecessarily create an std::string instance.
  57   for (auto &d : *CurrentDebugType) {
  58     if (d == DebugType)
  59       return true;
  60   }
  61   return false;
  62 }
  63
  64 /// Set the current debug type, as if the -debug-only=X
  65 /// option were specified.  Note that DebugFlag also needs to be set to true for
  66 /// debug output to be produced.
  67 ///
  68 void setCurrentDebugTypes(const char **Types, unsigned Count);
  69
  70 void setCurrentDebugType(const char *Type) {
  71   setCurrentDebugTypes(&Type, 1);
  72 }
  73
  74 void setCurrentDebugTypes(const char **Types, unsigned Count) {
  75   CurrentDebugType->clear();
  76   for (size_t T = 0; T < Count; ++T)
  77     CurrentDebugType->push_back(Types[T]);
  78 }
  79 } // namespace llvm
  80
  81 // All Debug.h functionality is a no-op in NDEBUG mode.
  82 #ifndef NDEBUG
  83
  84 namespace {
  85 struct CreateDebug {
  86   static void *call() {
  87     return new cl::opt<bool, true>("debug", cl::desc("Enable debug output"),
  88                                    cl::Hidden, cl::location(DebugFlag));
  89   }
  90 };
  91
  92 // -debug-buffer-size - Buffer the last N characters of debug output
  93 //until program termination.
  94 struct CreateDebugBufferSize {
  95   static void *call() {
  96     return new cl::opt<unsigned>(
  97         "debug-buffer-size",
  98         cl::desc("Buffer the last N characters of debug output "
  99                  "until program termination. "
 100                  "[default 0 -- immediate print-out]"),
 101         cl::Hidden, cl::init(0));
 102   }
 103 };
 104 } // namespace
 105
 106 // -debug - Command line option to enable the DEBUG statements in the passes.
 107 // This flag may only be enabled in debug builds.
 108 static ManagedStatic<cl::opt<bool, true>, CreateDebug> Debug;
 109 static ManagedStatic<cl::opt<unsigned>, CreateDebugBufferSize> DebugBufferSize;
 110
 111 namespace {
 112
 113 struct DebugOnlyOpt {
 114   void operator=(const std::string &Val) const {
 115     if (Val.empty())
 116       return;
 117     DebugFlag = true;
 118     SmallVector<StringRef,8> dbgTypes;
 119     StringRef(Val).split(dbgTypes, ',', -1, false);
 120     for (auto dbgType : dbgTypes)
 121       CurrentDebugType->push_back(std::string(dbgType));
 122   }
 123 };
 124 } // namespace
 125
 126 static DebugOnlyOpt DebugOnlyOptLoc;
 127
 128 namespace {
 129 struct CreateDebugOnly {
 130   static void *call() {
 131     return new cl::opt<DebugOnlyOpt, true, cl::parser<std::string>>(
 132         "debug-only",
 133         cl::desc("Enable a specific type of debug output (comma separated list "
 134                  "of types)"),
 135         cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
 136         cl::location(DebugOnlyOptLoc), cl::ValueRequired);
 137   }
 138 };
 139 } // namespace
 140
 141 static ManagedStatic<cl::opt<DebugOnlyOpt, true, cl::parser<std::string>>,
 142                      CreateDebugOnly>
 143     DebugOnly;
 144
 145 void llvm::initDebugOptions() {
 146   *Debug;
 147   *DebugBufferSize;
 148   *DebugOnly;
 149 }
 150
 151 // Signal handlers - dump debug output on termination.
 152 static void debug_user_sig_handler(void *Cookie) {
 153   // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
 154   // know that debug mode is enabled and dbgs() really is a
 155   // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
 156   // errs() but this will never be invoked.
 157   llvm::circular_raw_ostream &dbgout =
 158       static_cast<circular_raw_ostream &>(llvm::dbgs());
 159   dbgout.flushBufferWithBanner();
 160 }
 161
 162 /// dbgs - Return a circular-buffered debug stream.
 163 raw_ostream &llvm::dbgs() {
 164   // Do one-time initialization in a thread-safe way.
 165   static struct dbgstream {
 166     circular_raw_ostream strm;
 167
 168     dbgstream()
 169         : strm(errs(), "*** Debug Log Output ***\n",
 170                (!EnableDebugBuffering || !DebugFlag) ? 0 : *DebugBufferSize) {
 171       if (EnableDebugBuffering && DebugFlag && *DebugBufferSize != 0)
 172         // TODO: Add a handler for SIGUSER1-type signals so the user can
 173         // force a debug dump.
 174         sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
 175       // Otherwise we've already set the debug stream buffer size to
 176       // zero, disabling buffering so it will output directly to errs().
 177     }
 178   } thestrm;
 179
 180   return thestrm.strm;
 181 }
 182
 183 #else
 184 // Avoid "has no symbols" warning.
 185 namespace llvm {
 186   /// dbgs - Return errs().
 187   raw_ostream &dbgs() {
 188     return errs();
 189   }
 190 }
 191 void llvm::initDebugOptions() {}
 192 #endif
 193
 194 /// EnableDebugBuffering - Turn on signal handler installation.
 195 ///
 196 bool llvm::EnableDebugBuffering = false;