Function spt_init

app/redis-6.2.6/src/setproctitle.c:191–268

Initialize and populate SPT to allow a future setproctitle() * call. * * As setproctitle() basically needs to overwrite argv[0], we're * trying to determine what is the largest contiguous block * starting at argv[0] we can use for this purpose. * * As this range will overwrite some or all of the argv and environ * strings, a deep copy of these two arrays is performed. */

 * strings, a deep copy of these two arrays is performed.
 */
void spt_init(int argc, char *argv[]) {
        char **envp = environ;
	char *base, *end, *nul, *tmp;
	int i, error, envc;

	if (!(base = argv[0]))
		return;

	/* We start with end pointing at the end of argv[0] */
	nul = &base[strlen(base)];
	end = nul + 1;

	/* Attempt to extend end as far as we can, while making sure
	 * that the range between base and end is only allocated to
	 * argv, or anything that immediately follows argv (presumably
	 * envp).
	 */
	for (i = 0; i < argc || (i >= argc && argv[i]); i++) {
		if (!argv[i] || argv[i] < end)
			continue;

		if (end >= argv[i] && end <= argv[i] + strlen(argv[i]))
			end = argv[i] + strlen(argv[i]) + 1;
	}

	/* In case the envp array was not an immediate extension to argv,
	 * scan it explicitly.
	 */
	for (i = 0; envp[i]; i++) {
		if (envp[i] < end)
			continue;

		if (end >= envp[i] && end <= envp[i] + strlen(envp[i]))
			end = envp[i] + strlen(envp[i]) + 1;
	}
	envc = i;

	/* We're going to deep copy argv[], but argv[0] will still point to
	 * the old memory for the purpose of updating the title so we need
	 * to keep the original value elsewhere.
	 */
	if (!(SPT.arg0 = strdup(argv[0])))
		goto syerr;

#if __linux__
	if (!(tmp = strdup(program_invocation_name)))
		goto syerr;

	program_invocation_name = tmp;

	if (!(tmp = strdup(program_invocation_short_name)))
		goto syerr;

	program_invocation_short_name = tmp;
#elif __APPLE__
	if (!(tmp = strdup(getprogname())))
		goto syerr;