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 #undef isCurrentDebugType
  34 #undef setCurrentDebugType
  35 #undef setCurrentDebugTypes
  36
  37 using namespace llvm;
  38
  39 // Even though LLVM might be built with NDEBUG, define symbols that the code
  40 // built without NDEBUG can depend on via the llvm/Support/Debug.h header.
  41 namespace llvm {
  42 /// Exported boolean set by the -debug option.
  43 bool DebugFlag = false;
  44
  45 static ManagedStatic<std::vector<std::string>> CurrentDebugType;
  46
  47 /// Return true if the specified string is the debug type
  48 /// specified on the command line, or if none was specified on the command line
  49 /// with the -debug-only=X option.
  50 bool isCurrentDebugType(const char *DebugType) {
  51   if (CurrentDebugType->empty())
  52     return true;
  53   // See if DebugType is in list. Note: do not use find() as that forces us to
  54   // unnecessarily create an std::string instance.
  55   for (auto &d : *CurrentDebugType) {
  56     if (d == DebugType)
  57       return true;
  58   }
  59   return false;
  60 }
  61
  62 /// Set the current debug type, as if the -debug-only=X
  63 /// option were specified.  Note that DebugFlag also needs to be set to true for
  64 /// debug output to be produced.
  65 ///
  66 void setCurrentDebugTypes(const char **Types, unsigned Count);
  67
  68 void setCurrentDebugType(const char *Type) {
  69   setCurrentDebugTypes(&Type, 1);
  70 }
  71
  72 void setCurrentDebugTypes(const char **Types, unsigned Count) {
  73   CurrentDebugType->clear();
  74   for (size_t T = 0; T < Count; ++T)
  75     CurrentDebugType->push_back(Types[T]);
  76 }
  77 } // namespace llvm
  78
  79 // All Debug.h functionality is a no-op in NDEBUG mode.
  80 #ifndef NDEBUG
  81
  82 // -debug - Command line option to enable the DEBUG statements in the passes.
  83 // This flag may only be enabled in debug builds.
  84 static cl::opt<bool, true>
  85 Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
  86       cl::location(DebugFlag));
  87
  88 // -debug-buffer-size - Buffer the last N characters of debug output
  89 //until program termination.
  90 static cl::opt<unsigned>
  91 DebugBufferSize("debug-buffer-size",
  92                 cl::desc("Buffer the last N characters of debug output "
  93                          "until program termination. "
  94                          "[default 0 -- immediate print-out]"),
  95                 cl::Hidden,
  96                 cl::init(0));
  97
  98 namespace {
  99
 100 struct DebugOnlyOpt {
 101   void operator=(const std::string &Val) const {
 102     if (Val.empty())
 103       return;
 104     DebugFlag = true;
 105     SmallVector<StringRef,8> dbgTypes;
 106     StringRef(Val).split(dbgTypes, ',', -1, false);
 107     for (auto dbgType : dbgTypes)
 108       CurrentDebugType->push_back(dbgType);
 109   }
 110 };
 111
 112 }
 113
 114 static DebugOnlyOpt DebugOnlyOptLoc;
 115
 116 static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
 117 DebugOnly("debug-only", cl::desc("Enable a specific type of debug output (comma separated list of types)"),
 118           cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
 119           cl::location(DebugOnlyOptLoc), cl::ValueRequired);
 120 // Signal handlers - dump debug output on termination.
 121 static void debug_user_sig_handler(void *Cookie) {
 122   // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
 123   // know that debug mode is enabled and dbgs() really is a
 124   // circular_raw_ostream.  If NDEBUG is defined, then dbgs() ==
 125   // errs() but this will never be invoked.
 126   llvm::circular_raw_ostream &dbgout =
 127       static_cast<circular_raw_ostream &>(llvm::dbgs());
 128   dbgout.flushBufferWithBanner();
 129 }
 130
 131 /// dbgs - Return a circular-buffered debug stream.
 132 raw_ostream &llvm::dbgs() {
 133   // Do one-time initialization in a thread-safe way.
 134   static struct dbgstream {
 135     circular_raw_ostream strm;
 136
 137     dbgstream() :
 138         strm(errs(), "*** Debug Log Output ***\n",
 139              (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
 140       if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
 141         // TODO: Add a handler for SIGUSER1-type signals so the user can
 142         // force a debug dump.
 143         sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
 144       // Otherwise we've already set the debug stream buffer size to
 145       // zero, disabling buffering so it will output directly to errs().
 146     }
 147   } thestrm;
 148
 149   return thestrm.strm;
 150 }
 151
 152 #else
 153 // Avoid "has no symbols" warning.
 154 namespace llvm {
 155   /// dbgs - Return errs().
 156   raw_ostream &dbgs() {
 157     return errs();
 158   }
 159 }
 160
 161 #endif
 162
 163 /// EnableDebugBuffering - Turn on signal handler installation.
 164 ///
 165 bool llvm::EnableDebugBuffering = false;