recorder_trace_set - Man Page

recorder_trace_set — Configure tracing for event recorders
RECORDER_TRACE — Retrieve configured value

#include <recorder/recorder.h>

int recorder_trace_set(const char * trace_set);
#define RECORDER_TRACE(trace_name) ...

The recorder_trace_set() function configures tracing for event recorder, based on a trace description given in trace_set. The function accepts a NULL input. A typical usage is to call it twice at the beginning of the program, the first time to set some default configuration for important recorders such as warnings or errors, the second time to pass some environment variable letting users configure tracing easily.

    /* Activate tracing for all _warning and _error event recorders */
    recorder_trace_set(".*_(warning|error)");

    /* User trace configuration, possible overriding the above */
    recorder_trace_set(getenv("MY_PROGRAM_TRACES"));

The trace description is a space-delimited list of trace actions. Alternatively, a colon (:) can also be used as a separator.

Each trace action starts with a regular expression used to select event recorders by name. That regular expression can optionally be followed by an equal sign = itself followed by either a numerical value or a comma-separated list of names.

The function can return one of:

RECORDER_TRACE_OK

Thec trace description was successfully applied

RECORDER_TRACE_INVALID_NAME

One of the trace selection regular expressions is invalid.

RECORDER_TRACE_INVALID_VALUE

One of the trace configuration values is neither a numerical value nor a comma-separated list of names.

The program below records its input arguments, and crashes if passed crash as the first command-line argument.

#include <recorder/recorder.h>
#include <string.h>

RECORDER(program_args, 32, "Program command-line arguments");
int main(int argc, char **argv)
{
    int a;
    recorder_dump_on_common_signals(0, 0);
    for (a = 0; a < argc; a++)
        record(program_args, "Argument %d is %+s", a, argv[a]);

    if (argc >= 2 && strcmp(argv[1], "crash") == 0)
    {
        char *ptr = NULL;
        strcpy(ptr, argv[1]);
    }
}

When a crash occurs, previously recorded events are printed out on the console.

The program below is an instrumented version of the classical recursive Fibonacci computation. It uses several recorders corresponding to different types of events, and activates warnings and errors in a way that can be configured by setting an environment variable.

#include <recorder/recorder.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

RECORDER(fib_main,    32, "Loops in fib function");
RECORDER(fib_loops,   32, "Loops in fib function");
RECORDER(fib_warning, 32, "Warnings in fib function");
RECORDER(fib_error,   32, "Errors in fib function");

int fib(int n)
{
    if (n <= 1) {
        if (n < 0)
            record(fib_error, "fib is undefined for negative value %d", n);
        return n;
    }
    record(fib_loops, "Computing fib(%d)", n);
    int result = fib(n-1) + fib(n-2);
    record(fib_loops, "Computed fib(%d) = %d", n, result);
    return result;
}

int main(int argc, char **argv)
{
    int a;
    recorder_dump_on_common_signals(0, 0);
    recorder_trace_set(".*_warning=35 .*_error");
    recorder_trace_set(getenv("FIB_TRACES"));
    for (a = 1; a < argc; a++) {
        int n = atoi(argv[a]);
        if (n >= RECORDER_TRACE(fib_warning))
            record(fib_warning, "Computing for %d may take a while", n);
        printf("fib(%d) = %d0, n, fib(n));
        if (n >= RECORDER_TRACE(fib_warning))
            record(fib_warning, "Computation for %d finally completed", n);
    }
}

This program will produce an output similar to the following:

% fib 1 2 3 4 10 20 30 35 10 40 -1
fib(1) = 1
fib(2) = 1
fib(3) = 2
fib(4) = 3
fib(10) = 55
fib(20) = 6765
fib(30) = 832040
[2714667 0.177725] fib_warning: Computing for 35 may take a while
fib(35) = 9227465
[32575370 1.859156] fib_warning: Computation for 35 finally completed
fib(10) = 55
[32575547 1.859171] fib_warning: Computing for 40 may take a while
fib(40) = 102334155
[363735828 20.527882] fib_warning: Computation for 40 finally completed
[363735829 20.527887] fib_error: fib is undefined for negative value -1
fib(-1) = -1

The first column in trace outputs is the number of events that were recorded. THe second column is the time in seconds since the program started.

The same program can also be run with additional tracing or warnings, for example:

% FIB_TRACES="recorder_location fib_loops fib_warning=3" /tmp/fib 3 4
/tmp/fib.c:33:[82 0.000496] fib_warning: Computing for 3 may take a while
/tmp/fib.c:18:[83 0.000561] fib_loops: Computing fib(3)
/tmp/fib.c:18:[84 0.000570] fib_loops: Computing fib(2)
/tmp/fib.c:20:[85 0.000575] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[86 0.000581] fib_loops: Computed fib(3) = 2
fib(3) = 2
/tmp/fib.c:36:[87 0.000590] fib_warning: Computation for 3 finally completed
/tmp/fib.c:33:[88 0.000596] fib_warning: Computing for 4 may take a while
/tmp/fib.c:18:[89 0.000601] fib_loops: Computing fib(4)
/tmp/fib.c:18:[90 0.000607] fib_loops: Computing fib(3)
/tmp/fib.c:18:[91 0.000612] fib_loops: Computing fib(2)
/tmp/fib.c:20:[92 0.000619] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[93 0.000625] fib_loops: Computed fib(3) = 2
/tmp/fib.c:18:[94 0.000664] fib_loops: Computing fib(2)
/tmp/fib.c:20:[95 0.000707] fib_loops: Computed fib(2) = 1
/tmp/fib.c:20:[96 0.000724] fib_loops: Computed fib(4) = 3
fib(4) = 3
/tmp/fib.c:36:[97 0.000741] fib_warning: Computation for 4 finally completed

When a recorder is shared, incorrect data can be fetched by the client graphing program if the types and number of arguments is not consistent for all entries in the recorder.

Bugs should be reported using https://github.com/c3d/recorder/issues.

RECORDER_DEFINE(3), RECORDER_DECLARE(3)
recorder_dump(3), recorder_dump_for(3),
recorder_configure_output(3), recorder_configure_show(3)
recorder_configure_format(3), recorder_configure_type(3)

Additional documentation and tutorials can be found at https://github.com/c3d/recorder.

Written by Christophe de Dinechin

record(3), RECORDER(3), recorder_configure_output(3), recorder_configure_type(3), recorder_dump(3), recorder_scope(1).

The man pages RECORDER_TRACE(3) and RECORDER_TWEAK(3) are aliases of recorder_trace_set(3).