MLOG is a super-efficient logger for constrained systems like small embedded systems -- systems that cannot afford traditional string-based logging.

The idea is simple: instead of space-consuming log strings, 1-byte constants are defined in the code whose symbol name carries the text that is to be logged. For instance:

// Traditional logging:
logger("Inside function foo");

// Micro logging:
MLOG_INFO(Inside_function_foo);

The MLOG_INFO macro once statically allocates a one-byte symbol that looks more or less like this:

static const uint8_t MLOG_Comp_II_Inside_function_foo___;

Whenever execution reaches the MLOG_INFO macro, the address of the symbol is transferred to the log buffer. Later, on the receiving side, the original log string can be reconstructed with the help of the map file, where all MLOG symbols and their corresponding addresses can be found:

Address: Symbol:
------------------------------------------------------------
00656618 MLOG_MlogTest_II_Hello_there___
00656619 MLOG_MlogTest_II_Enter_AdvancedCharSearch___
0065661a MLOG_MlogTest_EE_ENSURE_text_must_not_be_null___
0065661b MLOG_MlogTest_WW_search_char_should_not_be_null___
0065661c MLOG_MlogTest_EE_invalid_search_mode___
0065661d MLOG_MlogTest_II_Exit_AdvancedCharSearch___
:

The benefit of the micro logging approach is clear: with traditional logging, 20 bytes would have to be stored and 20 bytes would have to be transmitted; with micro logging, only 1 byte needs to be stored and only 4 bytes need to be transmitted.

Currently, the following MLOG macros are implemented (refer to mlog_base.h):

• MLOG_INFO(m) Output text 'm' at log-level INFO.

• MLOG_WARN(m) Output text 'm' at log-level WARNING.

• MLOG_ERROR(m) Output text 'm' at log-level ERROR.

• MLOG_INFO_VALUE(m, v) Output text 'm' and an unsigned value 'v' at log-level INFO.

• MLOG_WARN_VALUE(m, v) Output text 'm' and an unsigned value 'v' at log-level WARNING.

• MLOG_ERROR_VALUE(m, v) Output text 'm' and an unsigned value 'v' at log-level ERROR.

• MLOG_ENSURE(e, m) If expresson 'e' is false, output text 'm'.

For running the provided example: just g++ and python3

If you want to extend/unit test MLOG itself, that is, if you want to run make in the top-level directory, you need Google Test/Google Mock. Please adapt paths in the Makefile accordingly.

The code for MLOG is highly portable and should compile with any contemporary C/C++ toolchain. generate_mlogmap.sh currently supports extraction of MLOG log symbols from gcc/g++ map files only.

Have a look at the README.md file in the example/ folder.