bitcoin/src/util/log.h

// Copyright (c) The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_UTIL_LOG_H
#define BITCOIN_UTIL_LOG_H

#include <logging/categories.h> // IWYU pragma: export
#include <tinyformat.h>
#include <util/check.h>

#include <cstdint>
#include <source_location>
#include <string>
#include <string_view>

/// Like std::source_location, but allowing to override the function name.
class SourceLocation
{
public:
    /// The func argument must be constructed from the C++11 __func__ macro.
    /// Ref: https://en.cppreference.com/w/cpp/language/function.html#func
    /// Non-static string literals are not supported.
    SourceLocation(const char* func,
                   std::source_location loc = std::source_location::current())
        : m_func{func}, m_loc{loc} {}

    std::string_view file_name() const { return m_loc.file_name(); }
    std::uint_least32_t line() const { return m_loc.line(); }
    std::string_view function_name_short() const { return m_func; }

private:
    std::string_view m_func;
    std::source_location m_loc;
};

namespace util::log {
/** Opaque to util::log; interpreted by consumers (e.g., BCLog::LogFlags). */
using Category = uint64_t;

enum class Level {
    Trace = 0, // High-volume or detailed logging for development/debugging
    Debug,     // Reasonably noisy logging, but still usable in production
    Info,      // Default
    Warning,
    Error,
};

struct Entry {
    Category category;
    Level level;
    bool should_ratelimit{false}; //!< Hint for consumers if this entry should be ratelimited
    SourceLocation source_loc;
    std::string message;
};

/** Return whether messages with specified category and level should be logged. Applications using
 * the logging library need to provide this. */
bool ShouldLog(Category category, Level level);

/** Send message to be logged. Applications using the logging library need to provide this. */
void Log(Entry entry);
} // namespace util::log

namespace BCLog {
//! Alias for compatibility. Prefer util::log::Level over BCLog::Level in new code.
using Level = util::log::Level;
} // namespace BCLog

template <typename... Args>
inline void LogPrintFormatInternal(SourceLocation&& source_loc, BCLog::LogFlags flag, BCLog::Level level, bool should_ratelimit, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
{
    std::string log_msg;
    try {
        log_msg = tfm::format(fmt, args...);
    } catch (tinyformat::format_error& fmterr) {
        log_msg = "Error \"" + std::string{fmterr.what()} + "\" while formatting log message: " + fmt.fmt;
    }
    util::log::Log(util::log::Entry{
        .category = flag,
        .level = level,
        .should_ratelimit = should_ratelimit,
        .source_loc = std::move(source_loc),
        .message = std::move(log_msg)});
}

// Allow __func__ to be used in any context without warnings:
// NOLINTNEXTLINE(bugprone-lambda-function-name)
#define LogPrintLevel_(category, level, should_ratelimit, ...) LogPrintFormatInternal(SourceLocation{__func__}, category, level, should_ratelimit, __VA_ARGS__)

// Log unconditionally. Uses basic rate limiting to mitigate disk filling attacks.
// Be conservative when using functions that unconditionally log to debug.log!
// It should not be the case that an inbound peer can fill up a user's storage
// with debug.log entries.
#define LogInfo(...) LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Info, /*should_ratelimit=*/true, __VA_ARGS__)
#define LogWarning(...) LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Warning, /*should_ratelimit=*/true, __VA_ARGS__)
#define LogError(...) LogPrintLevel_(BCLog::LogFlags::ALL, BCLog::Level::Error, /*should_ratelimit=*/true, __VA_ARGS__)

// Use a macro instead of a function for conditional logging to prevent
// evaluating arguments when logging for the category is not enabled.

// Log by prefixing the output with the passed category name and severity level. This logs conditionally if
// the category is allowed. No rate limiting is applied, because users specifying -debug are assumed to be
// developers or power users who are aware that -debug may cause excessive disk usage due to logging.
#define detail_LogIfCategoryAndLevelEnabled(category, level, ...)      \
    do {                                                               \
        if (util::log::ShouldLog((category), (level))) {               \
            bool rate_limit{level >= BCLog::Level::Info};              \
            Assume(!rate_limit); /*Only called with the levels below*/ \
            LogPrintLevel_(category, level, rate_limit, __VA_ARGS__);  \
        }                                                              \
    } while (0)

// Log conditionally, prefixing the output with the passed category name.
#define LogDebug(category, ...) detail_LogIfCategoryAndLevelEnabled(category, BCLog::Level::Debug, __VA_ARGS__)
#define LogTrace(category, ...) detail_LogIfCategoryAndLevelEnabled(category, BCLog::Level::Trace, __VA_ARGS__)

#endif // BITCOIN_UTIL_LOG_H