/*******************************************************************
 Print a backtrace of the stack to the debug log. 
********************************************************************/

#include "debug.h"
#include "config.h"
#include "util.h"

#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>

// HAVE_LIBUNWIND passed in from Makefile
#ifdef HAVE_LIBUNWIND
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#endif

#ifdef HAVE_LIBUNWIND
void log_stack_trace(char * program_name)
{
  	unw_cursor_t cursor; unw_context_t uc;
 	unw_word_t ip, sp, off;
        int status;
	unsigned i = 0;
	char procname[256];
	
	procname[sizeof(procname) - 1] = '\0';

	if (unw_getcontext(&uc) != 0) {
		INFO("unable to produce a stack trace with libunwind; unw_getcontext failure\n");
		return;
	}

	if (unw_init_local(&cursor, &uc) != 0) {
		INFO("unable to produce a stack trace with libunwind; unw_init_local failure\n");
		return;
	}

	INFO("%s: BACKTRACE:\n", program_name);

	while(1) {
            status = unw_step(&cursor);
            if(status == 0) {
                // INFO("unw_step: returned %d\n", status);
		break;
	    }
            if(status < 0) {
                INFO("unw_step error: %d\n", status);
                break;
            }
            // we got a valid stack frame to display
            ip = sp = 0;
	    unw_get_reg(&cursor, UNW_REG_IP, &ip);
	    unw_get_reg(&cursor, UNW_REG_SP, &sp);

	    switch (unw_get_proc_name(&cursor, procname, sizeof(procname) - 1, &off)) 
	    {
	    	case 0:
		    /* Name found. */
	    	case -UNW_ENOMEM:
		    /* Name truncated. */
		    INFO(" #%u %s + %#lx [ip=%#lx] [sp=%#lx]\n",
			 i, procname, (unsigned long)off,
			 (unsigned long)ip, (unsigned long) sp);
		    break;
	    	default:
	    	    /* case -UNW_ENOINFO: */
	            /* case -UNW_EUNSPEC: */
		    /* No symbol name found. */
		    INFO(" #%u %s [ip=%#lx] [sp=%#lx]\n",
			 i, "<unknown symbol>",
			 (unsigned long)ip, (unsigned long) sp);
	    }
	    i++;
        }
	return;
}

#else

// If we don't have libunwind, then we can't do a stack backtrace
void log_stack_trace(char * program_name)
{
	INFO("%s: unable to produce a stack trace on this platform; Need libunwind\n", program_name);
}

#endif