Enabling Debugging

[Volkan YAZICI]

Hi,

I'm trying to enable debbuging - that's (debug-enable 'backtrace) in
Scheme - from a C program on-the-fly. Therefore, as far as I
understand from the quite poorly documented guile manual, I should
use scm_debug_options() for this purpose. But I couldn't find any clue
about using this function in the neither manual, nor source code.

First, I tried sth like this:

static SCM
exception_handler(void *data, SCM tag, SCM throw_args)
{
    const char  *buf;
    int          len;
    SCM          scm;

    printf("\nJust got an error; tag is: [%s] ", (char *) data);

    buf = SCM_STRING_CHARS(tag);
    len = SCM_STRING_LENGTH(tag);
    while (len-- > 0)
        putchar(*buf++);

    printf("\nBacktrace:\n");
    scm = scm_backtrace();
    buf = SCM_STRING_CHARS(scm);
    len = SCM_STRING_LENGTH(scm);
    while (len-- > 0)
        putchar(*buf++);
    putchar('\n');

    return SCM_BOOL_F;
}

static void
main_prog(int argc, char **argv)
{   
    SCM res;
    
    scm_init_debug();
    res = gh_eval_str_with_catch("(string? (number?))",
                                 &exception_handler);
}

... and as you can imagine, it gave a segmentation fault in
"buf = SCM_STRING_CHARS(scm);" line. Then I tried to remove
scm_init_debug() call and mimic its behaviour like this with
no luck again:

/*
 * When I rename below _scm_debug_opts into scm_debug_opts (without an
 * underscore), it SegFaults in gh_enter().
 */
scm_t_option _scm_debug_opts[] = {
    {SCM_OPTION_BOOLEAN,    "breakpoints",      1,
        "Check for breakpoints."},
    {SCM_OPTION_BOOLEAN,    "trace",            1,
        "Trace mode."},
    {SCM_OPTION_BOOLEAN,    "procnames",        1,
        "Record procedure names at definition."},
    {SCM_OPTION_BOOLEAN,    "backwards",        1,
        "Display backtrace in anti-chronological order."},
    {SCM_OPTION_INTEGER,    "width",            79,
        "Maximal width of backtrace."},
    {SCM_OPTION_INTEGER,    "indent",           10,
        "Maximal indentation in backtrace."},
    {SCM_OPTION_INTEGER,    "frames",           3,
        "Maximum number of tail-recursive frames in backtrace."},
    {SCM_OPTION_INTEGER,    "maxdepth",         1000,
        "Maximal number of stored backtrace frames."},
    {SCM_OPTION_INTEGER,    "depth",            20,
        "Maximal length of printed backtrace."},
    {SCM_OPTION_BOOLEAN,    "backtrace",        1,
        "Show backtrace on error."},
    {SCM_OPTION_BOOLEAN,    "debug",            1,
        "Use the debugging evaluator."},
    {SCM_OPTION_INTEGER,    "stack",            20000,
            "Stack size limit (measured in words; 0 = no check)." },
    {SCM_OPTION_SCM,        "show-file-name",   1,
        "Show file names and line numbers in backtraces when not `#f'."
        "A value of `base' displays only base names, while `#t' "
        "displays full names."},
    {SCM_OPTION_BOOLEAN,    "warn-deprecated",  0,
        "Warn when deprecated features are used."}
};

#define SCM_N_DEBUG_OPTIONS 14

static void
main_prog(int argc, char **argv)
{
    SCM res;
    
    scm_init_opts(scm_debug_options,
                  _scm_debug_opts,
                  SCM_N_DEBUG_OPTIONS);
    res = gh_eval_str_with_catch("(string? (number?))",
                                 &exception_handler);
}

I'd be very appreciated if somebody can help me to figure out how to
enable/disable debugging on the fly. Also, comments and convention
suggestions about above used methods to catch all exceptions and
display them are welcome too.


Regards.