Repository: bitcoin/bitcoin
File: src/util/log.h (C/C++)

Code before:
struct SourceLocationHasher {
    size_t operator()(const SourceLocation& s) const noexcept
    {
        // Use CSipHasher(0, 0) as a simple way to get uniform distribution.
        return size_t(CSipHasher(0, 0)
                          .Write(s.line())
                          .Write(MakeUCharSpan(std::string_view{s.file_name()}))
                          .Finalize());
    }
};

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 {
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;
    }

Review comment (suggestion):
```suggestion
inline void LogPrintFormatInternal(SourceLocation&& source_loc, util::log::Category flag, BCLog::Level level, bool should_ratelimit, util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args)
```

Code after:
    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__)