/* (C)opyright MMVI Anselm R. Garbe <garbeam at gmail dot com>
 * See LICENSE file for license details.
 */
#include "dwm.h"
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>

/* extern */

void *
emallocz(unsigned int size) {
	void *res = calloc(1, size);

	if(!res)
		eprint("fatal: could not malloc() %u bytes\n", size);
	return res;
}

void
eprint(const char *errstr, ...) {
	va_list ap;

	va_start(ap, errstr);
	vfprintf(stderr, errstr, ap);
	va_end(ap);
	exit(EXIT_FAILURE);
}

void *
erealloc(void *ptr, unsigned int size) {
	void *res = realloc(ptr, size);

	if(!res)
		eprint("fatal: could not malloc() %u bytes\n", size);
	return res;
}

void
spawn(Arg *arg) {
	static char *shell = NULL;

	if(!shell && !(shell = getenv("SHELL")))
		shell = "/bin/sh";
	if(!arg->cmd)
		return;
	/* The double-fork construct avoids zombie processes and keeps the code
	 * clean from stupid signal handlers. */
	if(fork() == 0) {
		if(fork() == 0) {
			if(dpy)
				close(ConnectionNumber(dpy));
			setsid();
			execl(shell, shell, "-c", arg->cmd, (char *)NULL);
			fprintf(stderr, "dwm: execl '%s -c %s'", shell, arg->cmd);
			perror(" failed");
		}
		exit(0);
	}
	wait(0);
}

# Add the first 10 numbers, and return the result in the exit code.
#
# To run (from the subx directory):
#   $ ./subx translate examples/ex3.subx -o examples/ex3
#   $ ./subx run examples/ex3
# Expected result:
#   $ echo $?
#   55

== code 0x09000000
#   instruction                     effective address                                                   register    displacement    immediate
# . op          subop               mod             rm32          base        index         scale       r32
# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes

    # result: EBX = 0
    bb/copy-to-EBX  0/imm32
    # counter: ECX = 1
    b9/copy-to-ECX  1/imm32

$loop:
    # if (counter > 10) break
    81          7/subop/compare     3/mod/direct    1/rm32/ECX    .           .             .           .           .               0xa/imm32         # compare ECX
    7f/jump-if-greater  $exit/disp8
    # result += counter
    01/add                          3/mod/direct    3/rm32/EBX    .           .             .           1/r32/ECX   .               .                 # add ECX to EBX
    # ++counter
    41/increment-ECX
    # loop
    eb/jump  $loop/disp8

$exit:
    # syscall(exit, EBX)
    b8/copy-to-EAX  1/imm32/exit
    cd/syscall  0x80/imm8

# . . vim:nowrap:textwidth=0