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src: implement debug output utilities
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Implement utilities for easier debugging of Node.js core code,
inspired by the HTTP/2 debugging code. Debugging is, however,
implemented at runtime rather than at compile time, controlled
through a new `NODE_DEBUG_NATIVE=categories` environment variable.

The runtime overhead in the debugging-disabled case amounts to
1 well-cachable one-byte read per debug call.

PR-URL: #20987
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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addaleax committed May 31, 2018
1 parent 1b8e8e9 commit 45eeea4
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Showing 10 changed files with 174 additions and 0 deletions.
1 change: 1 addition & 0 deletions node.gyp
Original file line number Diff line number Diff line change
Expand Up @@ -367,6 +367,7 @@
'src/base_object-inl.h',
'src/connection_wrap.h',
'src/connect_wrap.h',
'src/debug_utils.h',
'src/env.h',
'src/env-inl.h',
'src/handle_wrap.h',
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5 changes: 5 additions & 0 deletions src/async_wrap.cc
Original file line number Diff line number Diff line change
Expand Up @@ -769,6 +769,11 @@ void EmitAsyncDestroy(Isolate* isolate, async_context asyncContext) {
Environment::GetCurrent(isolate), asyncContext.async_id);
}

std::string AsyncWrap::diagnostic_name() const {
return std::string(provider_names[provider_type()]) +
" (" + std::to_string(static_cast<int64_t>(async_id_)) + ")";
}

} // namespace node

NODE_BUILTIN_MODULE_CONTEXT_AWARE(async_wrap, node::AsyncWrap::Initialize)
1 change: 1 addition & 0 deletions src/async_wrap.h
Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,7 @@ class AsyncWrap : public BaseObject {
v8::Local<v8::Value>* argv);

virtual size_t self_size() const = 0;
virtual std::string diagnostic_name() const;

static void WeakCallback(const v8::WeakCallbackInfo<DestroyParam> &info);

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92 changes: 92 additions & 0 deletions src/debug_utils.h
Original file line number Diff line number Diff line change
@@ -0,0 +1,92 @@
#ifndef SRC_DEBUG_UTILS_H_
#define SRC_DEBUG_UTILS_H_

#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#include "async_wrap.h"
#include "env.h"
#include <string>

// Use FORCE_INLINE on functions that have a debug-category-enabled check first
// and then ideally only a single function call following it, to maintain
// performance for the common case (no debugging used).
#ifdef __GNUC__
#define FORCE_INLINE __attribute__((always_inline))
#define COLD_NOINLINE __attribute__((cold, noinline))
#else
#define FORCE_INLINE
#define COLD_NOINLINE
#endif

namespace node {

template <typename... Args>
inline void FORCE_INLINE Debug(Environment* env,
DebugCategory cat,
const char* format,
Args&&... args) {
if (!UNLIKELY(env->debug_enabled(cat)))
return;
fprintf(stderr, format, std::forward<Args>(args)...);
}

inline void FORCE_INLINE Debug(Environment* env,
DebugCategory cat,
const char* message) {
if (!UNLIKELY(env->debug_enabled(cat)))
return;
fprintf(stderr, "%s", message);
}

template <typename... Args>
inline void Debug(Environment* env,
DebugCategory cat,
const std::string& format,
Args&&... args) {
Debug(env, cat, format.c_str(), std::forward<Args>(args)...);
}

// Used internally by the 'real' Debug(AsyncWrap*, ...) functions below, so that
// the FORCE_INLINE flag on them doesn't apply to the contents of this function
// as well.
// We apply COLD_NOINLINE to tell the compiler that it's not worth optimizing
// this function for speed and it should rather focus on keeping it out of
// hot code paths. In particular, we want to keep the string concatenating code
// out of the function containing the original `Debug()` call.
template <typename... Args>
void COLD_NOINLINE UnconditionalAsyncWrapDebug(AsyncWrap* async_wrap,
const char* format,
Args&&... args) {
Debug(async_wrap->env(),
static_cast<DebugCategory>(async_wrap->provider_type()),
async_wrap->diagnostic_name() + " " + format + "\n",
std::forward<Args>(args)...);
}

template <typename... Args>
inline void FORCE_INLINE Debug(AsyncWrap* async_wrap,
const char* format,
Args&&... args) {
#ifdef DEBUG
CHECK_NOT_NULL(async_wrap);
#endif
DebugCategory cat =
static_cast<DebugCategory>(async_wrap->provider_type());
if (!UNLIKELY(async_wrap->env()->debug_enabled(cat)))
return;
UnconditionalAsyncWrapDebug(async_wrap, format, std::forward<Args>(args)...);
}

template <typename... Args>
inline void FORCE_INLINE Debug(AsyncWrap* async_wrap,
const std::string& format,
Args&&... args) {
Debug(async_wrap, format.c_str(), std::forward<Args>(args)...);
}


} // namespace node

#endif // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS

#endif // SRC_DEBUG_UTILS_H_
18 changes: 18 additions & 0 deletions src/env-inl.h
Original file line number Diff line number Diff line change
Expand Up @@ -519,6 +519,24 @@ inline void Environment::set_http2_state(
http2_state_ = std::move(buffer);
}

bool Environment::debug_enabled(DebugCategory category) const {
#ifdef DEBUG
CHECK_GE(static_cast<int>(category), 0);
CHECK_LT(static_cast<int>(category),
static_cast<int>(DebugCategory::CATEGORY_COUNT));
#endif
return debug_enabled_[static_cast<int>(category)];
}

void Environment::set_debug_enabled(DebugCategory category, bool enabled) {
#ifdef DEBUG
CHECK_GE(static_cast<int>(category), 0);
CHECK_LT(static_cast<int>(category),
static_cast<int>(DebugCategory::CATEGORY_COUNT));
#endif
debug_enabled_[static_cast<int>(category)] = enabled;
}

inline AliasedBuffer<double, v8::Float64Array>*
Environment::fs_stats_field_array() {
return &fs_stats_field_array_;
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26 changes: 26 additions & 0 deletions src/env.cc
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Expand Up @@ -130,6 +130,10 @@ Environment::Environment(IsolateData* isolate_data,

// By default, always abort when --abort-on-uncaught-exception was passed.
should_abort_on_uncaught_toggle_[0] = 1;

std::string debug_cats;
SafeGetenv("NODE_DEBUG_NATIVE", &debug_cats);
set_debug_categories(debug_cats, true);
}

Environment::~Environment() {
Expand Down Expand Up @@ -496,6 +500,28 @@ Local<Value> Environment::GetNow() {
}


void Environment::set_debug_categories(const std::string& cats, bool enabled) {
std::string debug_categories = cats;
while (!debug_categories.empty()) {
std::string::size_type comma_pos = debug_categories.find(',');
std::string wanted = ToLower(debug_categories.substr(0, comma_pos));

#define V(name) \
{ \
static const std::string available_category = ToLower(#name); \
if (available_category.find(wanted) != std::string::npos) \
set_debug_enabled(DebugCategory::name, enabled); \
}

DEBUG_CATEGORY_NAMES(V)

if (comma_pos == std::string::npos)
break;
// Use everything after the `,` as the list for the next iteration.
debug_categories = debug_categories.substr(comma_pos);
}
}

void CollectExceptionInfo(Environment* env,
v8::Local<v8::Object> obj,
int errorno,
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19 changes: 19 additions & 0 deletions src/env.h
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Expand Up @@ -398,6 +398,19 @@ struct ContextInfo {
bool is_default = false;
};

// Listing the AsyncWrap provider types first enables us to cast directly
// from a provider type to a debug category. Currently no other debug
// categories are available.
#define DEBUG_CATEGORY_NAMES(V) \
NODE_ASYNC_PROVIDER_TYPES(V)

enum class DebugCategory {
#define V(name) name,
DEBUG_CATEGORY_NAMES(V)
#undef V
CATEGORY_COUNT
};

class Environment {
public:
class AsyncHooks {
Expand Down Expand Up @@ -654,6 +667,10 @@ class Environment {
inline http2::Http2State* http2_state() const;
inline void set_http2_state(std::unique_ptr<http2::Http2State> state);

inline bool debug_enabled(DebugCategory category) const;
inline void set_debug_enabled(DebugCategory category, bool enabled);
void set_debug_categories(const std::string& cats, bool enabled);

inline AliasedBuffer<double, v8::Float64Array>* fs_stats_field_array();

// stat fields contains twice the number of entries because `fs.StatWatcher`
Expand Down Expand Up @@ -853,6 +870,8 @@ class Environment {
bool http_parser_buffer_in_use_ = false;
std::unique_ptr<http2::Http2State> http2_state_;

bool debug_enabled_[static_cast<int>(DebugCategory::CATEGORY_COUNT)] = {0};

AliasedBuffer<double, v8::Float64Array> fs_stats_field_array_;

std::vector<std::unique_ptr<fs::FileHandleReadWrap>>
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3 changes: 3 additions & 0 deletions src/node.cc
Original file line number Diff line number Diff line change
Expand Up @@ -3302,6 +3302,9 @@ static void PrintHelp() {
"Environment variables:\n"
"NODE_DEBUG ','-separated list of core modules\n"
" that should print debug information\n"
"NODE_DEBUG_NATIVE ','-separated list of C++ core debug\n"
" categories that should print debug\n"
" output\n"
"NODE_DISABLE_COLORS set to 1 to disable colors in the REPL\n"
"NODE_EXTRA_CA_CERTS path to additional CA certificates\n"
" file\n"
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7 changes: 7 additions & 0 deletions src/util-inl.h
Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,13 @@ char ToLower(char c) {
return c >= 'A' && c <= 'Z' ? c + ('a' - 'A') : c;
}

std::string ToLower(const std::string& in) {
std::string out(in.size(), 0);
for (size_t i = 0; i < in.size(); ++i)
out[i] = ToLower(in[i]);
return out;
}

bool StringEqualNoCase(const char* a, const char* b) {
do {
if (*a == '\0')
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2 changes: 2 additions & 0 deletions src/util.h
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
#include <stdlib.h>
#include <string.h>

#include <string>
#include <functional> // std::function

namespace node {
Expand Down Expand Up @@ -250,6 +251,7 @@ inline void SwapBytes64(char* data, size_t nbytes);

// tolower() is locale-sensitive. Use ToLower() instead.
inline char ToLower(char c);
inline std::string ToLower(const std::string& in);

// strcasecmp() is locale-sensitive. Use StringEqualNoCase() instead.
inline bool StringEqualNoCase(const char* a, const char* b);
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