teflib

Lightweight C++ tracing library to produce data in Google's Trace Event Format (TEF).

What is it?

The Chrome browser has a tool at chrome://tracing which allows for easy visualization and examination of timing measurements. It is most commonly used for webpage JavaScript performance analysis however it will load any correctly formatted data file.

teflib is a small utility for measuring events in a C++ project and then properly formatting that data so it can be loaded by the chrome://tracing tool. It does not yet support 100% of the TEF feature set, but it is complete enough for many purposes.

How to use teflib?

teflib consists of two files: trace.h and trace.cpp. It requires at least C++-14 and depends on the fmt library. The files can be embedded in your own project, or they can be compiled into a library and linked as a dependency.

The simplest pattern is to sprinkle teflib's helper macros in your code:

// main.cpp

...

// in main global context:
# include "path/to/teflib/trace.h"
TRACE_GLOBAL_INIT;

...

int main() {
    // optional: at the start of main():
    TRACE_PROCESS("application name");

    // optional: at start of any thread:
    TRACE_THREAD("thread name");
 
    ...
   
    while (looping) { 
        // in main loop:
        TRACE_MAINLOOP;

        ...
    } // end mainloop

    // after main loop, before exit:
    TRACE_CLEANUP;
    
    ...

    return value;
} // end of main()

Wherever you want to measure duration add a TRACE_CONTEXT() macro, one per context:

  ...
    while (something_is_true) {
        TRACE_CONTEXT("loop", "category");

        ...

        // use curly braces to define context scope for more detailed TRACE_CONTEXT
        {
            TRACE_CONTEXT("thing one", "category");
            do_thing_one();
        }
        {
            TRACE_CONTEXT("thing_two", "category");
            do_thing_two();
        }
        ...

        // optionally add 'args' to the context to expose extra to the tracing browser
        TRACE_CONTEXT_ARGs("\"num_things\":", num_things);
    }

There is a little more to it because tracing shouldn't be enabled by default: you would normally toggle it on/off with one or more triggers. There are many ways to do this and the best way will depend on your application's interface. Please examine the teflib example source code to see one way to do it.

To build:

1. In teflib/ main directory:
   1. mkdir build
   2. cd build
2. In teflib/build/ directory:
   1. cmake -DCMAKE_BUILD_TYPE=Release ../
   2. make