indentlog -- logging with automatic call-graph indenting

Indentlog is a lightweight header-only library for console logging.

Features

• header-only; nothing to link
• easy-to-read format uses indenting to show call structure. indentation has user-controlled upper limit to preserve readability with deeply nested call graphs
• colorized output using vt100 color codes (ansi or xterm)
• automatically captures + displays timestamp, function name and code location. supports several function-name formats to reflect tradeoff readability for precision
• application code may issue logging code that contains embedded newlines and/or color escapes; logger preserves indentation.
• logger is 'truthy' -> only pay for formatting when entry points is enabled.
• also provides family of convenience stream-inserters

Examples

1

#include "indentlog/scope.hpp"

using namespace xo;

void inner(int x) {
    scope log(XO_ENTER0(always), ":x ", x);
}

void outer(int y) {
    scope log(XO_ENTER0(always), ":y ", y);

    inner(2*y);
}

int
main(int argc, char ** argv) {
    outer(123);
}

output:

• indentlog types are provided in the xo namespace. macros are prefixed with XO_
• indentation reflects call structure. We don't see anything for main(), since we didn't put any logging there

2 slightly more elaborate example

/* examples ex2/ex2.cpp */

#include "indentlog/scope.hpp"

using namespace xo;

int
fib(int n) {
    scope log(XO_ENTER0(info), ":n ", n);

    int retval = 1;

    if (n >= 2) {
        retval = fib(n - 1) + fib(n - 2);
        log && log(":n ", n);
    }

    log.end_scope("<- :retval ", retval);

    return retval;
}

int
main(int argc, char ** argv) {
    log_config::min_log_level = xo::log_level::info;
    log_config::indent_width = 4;

    int n = 4;

    scope log(XO_ENTER0(info), ":n ", 4);

    int fn = fib(n);

    log && log(":n ", n);
    log && log("<- :fib(n) ", fn);
}

output:

• global configuration settings live in the xo::log_config class. see log_config.hpp
• the recommended form log && log(...) tests whether logging at this site is enabled /before/ evaluating/formatting the log message; when logging is disabled, this saves the cost of computing and formatting that message.

3 example exposing runtime configuration options

/* examples ex3/ex3.cpp */

#include "indentlog/scope.hpp"

using namespace xo;

int
fib(int n) {
    scope log(XO_ENTER0(info), tag("n", n));

    int retval = 1;

    if (n >= 2) {
        retval = fib(n - 1) + fib(n - 2);
    }

    log.end_scope(tag("n", n), " <-", xtag("retval", retval));

    return retval;
}

int
main(int argc, char ** argv) {
    log_config::min_log_level = log_level::info;
    log_config::time_enabled = true;
    log_config::time_local_flag = true;
    log_config::style = FS_Streamlined;
    log_config::indent_width = 4;
    log_config::max_indent_width = 30;
    log_config::location_tab = 80;
    log_config::encoding = CE_Xterm;
    log_config::function_entry_color = 69;
    log_config::function_exit_color = 70;
    log_config::code_location_color = 166;

    int n = 3;

    scope log(XO_ENTER0(info), ":n ", 4);

    int fn = fib(n);

    log && log(tag("n", n));
    log && log("<-", xtag("fib(n)", fn));
}

/* ex3/ex3.cpp */

output:

4 example: function signatures

/* @file ex4.cpp */

#include "indentlog/scope.hpp"

using namespace xo;

class Quadratic {
public:
    Quadratic(double a, double b, double c) : a_{a}, b_{b}, c_{c} {}

    double operator() (double x) const {
        scope log(XO_ENTER0(info), tag("a", a_), xtag("b", b_), xtag("c", c_), xtag("x", x));

        double retval = (a_ * x * x) + (b_ * x) + c_;

        log.end_scope("<-", xtag("retval", retval));

        return retval;
    }

private:
    double a_ = 0.0;;
    double b_ = 0.0;
    double c_ = 0.0;
};

int
main(int argc, char ** argv) {
    //log_config::style  = FS_Pretty;
    log_config::style  = FS_Streamlined;
    log_config::min_log_level = log_level::info;

    scope log(XO_ENTER0(info));

    Quadratic quadratic(2.0, -5.0, 7.0);

    double x = 3.0;
    double r = 0.0;

    log_config::style  = FS_Pretty;

    r = quadratic(x);

    log_config::style = FS_Streamlined;

    r = quadratic(x);

    log_config::style = FS_Simple;

    r = quadratic(x);
}

/* end ex4.cpp */

output: