Logging

lbuild module: modm:debug

The modm::log::Logger uses a modm::IOStream to read messages and write them to a given output device.

Write a log message with streams:

MODM_LOG_DEBUG << "i=" << i << ", y=" << y << modm::flush;

The name of the stream represents the log level of the message. Available are:

• MODM_LOG_DEBUG
• MODM_LOG_INFO
• MODM_LOG_WARNING
• MODM_LOG_ERROR

A log message can also be generated separately:

int a[3] = {1,2,3};
MODM_LOG_DEBUG << "a = ";
for(int i = 0; i < sizeof(a); ++i) {
    MODM_LOG_DEBUG << a[i] << ", ";
}
MODM_LOG_DEBUG << modm::flush;

Flow of a call

This is to give an estimation how many resources a call of the logger use. All considerations are for a PC program.

The given call is:

MODM_LOG_DEBUG << 123456;

The macro resolves to:

if (MODM_LOG_LEVEL <= modm::log::DEBUG)
    modm::log::debug

• modm::log::debug is an instance of modm::Logger: Call of modm::Logger::operator << (T) (with T = int32_t) which is inline
• IOStream::operator << (T) (with T = int32_t) is inline
• IOStream::writeInteger(int32_t)
• IOStream::writeInteger(int32_t) will create the formatted string
• virtual call of IODevice::write(const char*)
• redirect to std::cout

In sum there are two nested method calls with one of them being virtual.

Dependencies