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//===-- Debug.cpp - An easy way to add debug output to your code ----------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file implements a handy way of adding debugging information to your
// code, without it being enabled all of the time, and without having to add
// command line options to enable it.
// In particular, just wrap your code with the LLVM_DEBUG() macro, and it will
// be enabled automatically if you specify '-debug' on the command-line.
// Alternatively, you can also use the SET_DEBUG_TYPE("foo") macro to specify
// that your debug code belongs to class "foo". Then, on the command line, you
// can specify '-debug-only=foo' to enable JUST the debug information for the
// foo class.
// When compiling without assertions, the -debug-* options and all code in
// LLVM_DEBUG() statements disappears, so it does not affect the runtime of the
// code.
#include "llvm/Support/Debug.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/circular_raw_ostream.h"
#include "llvm/Support/raw_ostream.h"
#undef isCurrentDebugType
#undef setCurrentDebugType
#undef setCurrentDebugTypes
using namespace llvm;
// Even though LLVM might be built with NDEBUG, define symbols that the code
// built without NDEBUG can depend on via the llvm/Support/Debug.h header.
namespace llvm {
/// Exported boolean set by the -debug option.
bool DebugFlag = false;
static ManagedStatic<std::vector<std::string>> CurrentDebugType;
/// Return true if the specified string is the debug type
/// specified on the command line, or if none was specified on the command line
/// with the -debug-only=X option.
bool isCurrentDebugType(const char *DebugType) {
if (CurrentDebugType->empty())
return true;
// See if DebugType is in list. Note: do not use find() as that forces us to
// unnecessarily create an std::string instance.
for (auto &d : *CurrentDebugType) {
if (d == DebugType)
return true;
return false;
/// Set the current debug type, as if the -debug-only=X
/// option were specified. Note that DebugFlag also needs to be set to true for
/// debug output to be produced.
void setCurrentDebugTypes(const char **Types, unsigned Count);
void setCurrentDebugType(const char *Type) {
setCurrentDebugTypes(&Type, 1);
void setCurrentDebugTypes(const char **Types, unsigned Count) {
for (size_t T = 0; T < Count; ++T)
} // namespace llvm
// All Debug.h functionality is a no-op in NDEBUG mode.
#ifndef NDEBUG
// -debug - Command line option to enable the DEBUG statements in the passes.
// This flag may only be enabled in debug builds.
static cl::opt<bool, true>
Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
// -debug-buffer-size - Buffer the last N characters of debug output
//until program termination.
static cl::opt<unsigned>
cl::desc("Buffer the last N characters of debug output "
"until program termination. "
"[default 0 -- immediate print-out]"),
namespace {
struct DebugOnlyOpt {
void operator=(const std::string &Val) const {
if (Val.empty())
DebugFlag = true;
SmallVector<StringRef,8> dbgTypes;
StringRef(Val).split(dbgTypes, ',', -1, false);
for (auto dbgType : dbgTypes)
static DebugOnlyOpt DebugOnlyOptLoc;
static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
DebugOnly("debug-only", cl::desc("Enable a specific type of debug output (comma separated list of types)"),
cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
cl::location(DebugOnlyOptLoc), cl::ValueRequired);
// Signal handlers - dump debug output on termination.
static void debug_user_sig_handler(void *Cookie) {
// This is a bit sneaky. Since this is under #ifndef NDEBUG, we
// know that debug mode is enabled and dbgs() really is a
// circular_raw_ostream. If NDEBUG is defined, then dbgs() ==
// errs() but this will never be invoked.
llvm::circular_raw_ostream &dbgout =
static_cast<circular_raw_ostream &>(llvm::dbgs());
/// dbgs - Return a circular-buffered debug stream.
raw_ostream &llvm::dbgs() {
// Do one-time initialization in a thread-safe way.
static struct dbgstream {
circular_raw_ostream strm;
dbgstream() :
strm(errs(), "*** Debug Log Output ***\n",
(!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
// TODO: Add a handler for SIGUSER1-type signals so the user can
// force a debug dump.
sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
// Otherwise we've already set the debug stream buffer size to
// zero, disabling buffering so it will output directly to errs().
} thestrm;
return thestrm.strm;
// Avoid "has no symbols" warning.
namespace llvm {
/// dbgs - Return errs().
raw_ostream &dbgs() {
return errs();
/// EnableDebugBuffering - Turn on signal handler installation.
bool llvm::EnableDebugBuffering = false;