recorder_dump(3)

NAME
recorder_dump - Dump all recorder entries
recorder_dump_for - Dump selected recorders
recorder_sort - Fine-controlled recorder dump
recorder_dump_on_signal - Dump the recorder when receiving a signal
recorder_dump_on_common_signals - Dump the recorder for standard signals

SYNOPSIS
#include <recorder/recorder.h>

typedef unsigned (*recorder_show_fn) (const char *text,
                                      size_tlen,
                                      void *output);
typedef void (*recorder_format_fn)(recorder_show_fn show,
                                   void *output,
                                   const char * label,
                                   const char *location,
                                   uintptr_torder,
                                   uintptr_ttimestamp,
                                   const char *message);
typedef size_t (*recorder_type_fn)(intptr_t trace,
                                   const char *format,
                                   char *buffer,
                                   size_tlength,
                                   uintptr_tdata);

unsigned recorder_dump(void);
unsigned recorder_dump_for(const char *pattern);
unsigned recorder_sort(const char *pattern,
                       recorder_format_fn format,
                       recorder_show_fn show,
                       void * show_arg);
void recorder_dump_on_signal(int signal);
void recorder_dump_on_common_signals(unsigned add,
                                     unsigned remove);

DESCRIPTION

The recorder_dump() function dumps the content of all the event recorders, in the order in which they were recorded. The recorder_dump_for() function only dumps the recorders selected by the regular expression pattern. The recorder_sort() function dumps the recorders selected by regular expression pattern using format to format an event record, show to show it, and passing show_arg to the function show.

Calls to recorder_dump() and recorder_dump_for() are equivalents to calls to recorder_sort where standard default values for format, show and arg. These values can be changed using recorder_configure_format(3), recorder_configure_show(3) and recorder_configure_output(3) respectively.

The recorder_dump_on_signal() function ensures that recorder_dump() is called if the programs receives the given signal. The recorder_dump_on_common_signals() ensures that a recorder dump happens if any of a common set of signals is received by the program (SIGQUIT, SIGILL, SIGABRT, SIGBUS, SIGSEGV, SIGSYS, SIGXCPU, SIGXFSZ, SIGINFO, SIGUSR1, SIGUSR2, SIGSTKFLT and SIGPWR, insofar as they are defined for the operating system). The add and remove are bit masks that can be used to add or remove other signals compared to the default list.

RETURN VALUE

The recorder_dump(), recorder_dump_for() and recorder_sort() functions return the number of event records that were dumped.

ENVIRONMENT VARIABLES

The recorder_dump_on_common_signals() function also reads the following environment variables:

RECORDER_TRACES
    A trace description, in the format expected by recorder_trace_set(3).

RECORDER_TWEAKS
    Like RECORDER_TRACES, but normally used for tweaking configuration values as opposed to tracing.

RECORDER_DUMP
    Activates a background thread to dump the given pattern at regular intervals.

EXAMPLES

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) = %d, 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

BUGS

The current signal handling mechanism does not yet use sigaltstack(2) and consequently is not robust to stack overflow. It is also known to fail for repeated signals. SIGINFO (and the associated Control-T keyboard shortcut) do not exist on Linux, which is a pity.

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

SEE ALSO
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.

AUTHOR
Written by Christophe de Dinechin