Macro Documentation

Q_DECLARE_LOGGING_CATEGORY(name)

Declares a logging category name. The macro can be used to declare a common logging category shared in different parts of the program.

This macro must be used outside of a class or method.

This function was introduced in Qt 5.2.

See also Q_LOGGING_CATEGORY().

Q_LOGGING_CATEGORY(name, string, msgType)

Defines a logging category name, and makes it configurable under the string identifier. By default, messages of QtMsgType msgType and more severe are enabled, types with a lower severity are disabled.

Only one translation unit in a library or executable can define a category with a specific name. The implicitly-defined QLoggingCategory object is created on first use, in a thread-safe manner.

This macro must be used outside of a class or method. It is only defined if variadic macros are supported.

This function was introduced in Qt 5.4.

See also Q_DECLARE_LOGGING_CATEGORY().

Q_LOGGING_CATEGORY(name, string)

Defines a logging category name, and makes it configurable under the string identifier. By default, all message types are enabled.

Only one translation unit in a library or executable can define a category with a specific name. The implicitly-defined QLoggingCategory object is created on first use, in a thread-safe manner.

This macro must be used outside of a class or method.

This function was introduced in Qt 5.2.

See also Q_DECLARE_LOGGING_CATEGORY().

qCCritical(category, const char *message, ...)

Logs a critical message, message, in the logging category, category. message may contain place holders to be replaced by additional arguments, similar to the C printf() function.

Example:

    QLoggingCategory category("driver.usb");
    qCCritical(category, "a critical message logged into category %s", category.categoryName());

Note: If the critical output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.3.

See also qCritical().

qCCritical(category)

Returns an output stream for critical messages in the logging category, category.

The macro expands to code that checks whether QLoggingCategory::isCriticalEnabled() evaluates to true. If so, the stream arguments are processed and sent to the message handler.

Example:

    QLoggingCategory category("driver.usb");
    qCCritical(category) << "a critical message";

Note: If the critical output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.2.

See also qCritical().

qCDebug(category, const char *message, ...)

Logs a debug message, message, in the logging category, category. message may contain place holders to be replaced by additional arguments, similar to the C printf() function.

Example:

    QLoggingCategory category("driver.usb");
    qCDebug(category, "a debug message logged into category %s", category.categoryName());

Note: Arguments aren't processed if the debug output for that category is not enabled, so don't rely on any side effects.

This function was introduced in Qt 5.3.

See also qDebug().

qCDebug(category)

Returns an output stream for debug messages in the logging category, category.

The macro expands to code that checks whether QLoggingCategory::isDebugEnabled() evaluates to true. If so, the stream arguments are processed and sent to the message handler.

Example:

    QLoggingCategory category("driver.usb");
    qCDebug(category) << "a debug message";

Note: Arguments aren't processed if the debug output for that category is not enabled, so don't rely on any side effects.

This function was introduced in Qt 5.2.

See also qDebug().

qCInfo(category, const char *message, ...)

Logs an informational message, message, in the logging category, category. message may contain place holders to be replaced by additional arguments, similar to the C printf() function.

Example:

    QLoggingCategory category("driver.usb");
    qCInfo(category, "an informational message logged into category %s", category.categoryName());

Note: If the debug output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.5.

See also qInfo().

qCInfo(category)

Returns an output stream for informational messages in the logging category, category.

The macro expands to code that checks whether QLoggingCategory::isInfoEnabled() evaluates to true. If so, the stream arguments are processed and sent to the message handler.

Example:

    QLoggingCategory category("driver.usb");
    qCInfo(category) << "an informational message";

Note: If the debug output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.5.

See also qInfo().

qCWarning(category, const char *message, ...)

Logs a warning message, message, in the logging category, category. message may contain place holders to be replaced by additional arguments, similar to the C printf() function.

Example:

    QLoggingCategory category("driver.usb");
    qCWarning(category, "a warning message logged into category %s", category.categoryName());

Note: If the warning output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.3.

See also qWarning().

qCWarning(category)

Returns an output stream for warning messages in the logging category, category.

The macro expands to code that checks whether QLoggingCategory::isWarningEnabled() evaluates to true. If so, the stream arguments are processed and sent to the message handler.

Example:

    QLoggingCategory category("driver.usb");
    qCWarning(category) << "a warning message";

Note: If the warning output for a particular category isn't enabled, arguments won't be processed, so don't rely on any side effects.

This function was introduced in Qt 5.2.

See also qWarning().