set	prototyped
hdr	nc,exec_attr
mem	exception.name,_exception.name math.h
lib	setreuid,setregid,nice,fork,spawnveg,fchdir
lib	pathnative,pathposix,uwin_path,uwin_unpath,fts_notify
lib	memcntl sys/mman.h
lib	getexecuser,free_execattr exec_attr.h -lsecdb

reference	unistd.h

extern	nice		int	(int)
extern	setreuid	int	(uid_t,uid_t)
extern	setregid	int	(gid_t,gid_t)

tst	note{ determining extra bytes per argument for arguments list }end output{
	/*
	 * Figure out if this OS requires extra bytes per argument
	 * in the arguments list of a process.
	 * Outputs an appropriate #define ARG_EXTRA_BYTES.
	 * Without this, 'command -x' failed with E2BIG on macOS, Linux and Solaris
	 * even if all the arguments should fit in ARG_MAX based on their length.
	 */

	/* AST includes */
	#include <ast.h>
	#include <error.h>
	#include <sfio.h>
	#include <stak.h>
	#include <wait.h>

	/* Standard includes */
	#include <errno.h>

	int main(int argc,char *argv[])
	{
		int extra_bytes = 0, envlen, argmax, i;
		pid_t childpid;

		error_info.id="ARG_EXTRA_BYTES test (parent)";
		while(1)
		{
			envlen = 0;
			for(i=0; argv[i]; i++)
				envlen += strlen(argv[i]) + 1 + extra_bytes;
			envlen += 1 + extra_bytes;	/* final null element */
			for(i=0; environ[i]; i++)
				envlen += strlen(environ[i]) + 1 + extra_bytes;
			envlen += 1 + extra_bytes;	/* final null element */
			argmax = (int)astconf_long(CONF_ARG_MAX) - envlen;
			if (argmax < 2048)
			{
				error(ERROR_ERROR|2, "argmax too small");
				return 1;
			}
			if(!(childpid = fork()))
			{
				/* child */
				int bytec;

				error_info.id="ARG_EXTRA_BYTES test (child)";
				argv = (char **)stakalloc((argmax / 2 + 1) * sizeof(char*));
				argc = bytec = 0;
				while(bytec < argmax)
				{
					if(argc==0)
						argv[argc] = "/usr/bin/env";
					else if(argc==1)
						argv[argc] = "true";
					else
						argv[argc] = "x";
					/* also add 1 for terminating zero byte */
					bytec += strlen(argv[argc]) + 1 + extra_bytes;
					argc++;
				}
				argv[argc] = (char*)0;
				if(execve(argv[0], argv, environ) < 0)
				{
					if(errno == E2BIG)
						return 1;
					else
					{
						error(ERROR_SYSTEM|2, "execve failed");
						return 2;
					}
				}
				error(ERROR_SYSTEM|2, "[BUG] we should never get here!");
				return 2;
			}
			else
			{
				/* parent */
				int exitstatus;

				if (waitpid(childpid,&i,0) < 0)
				{
					error(ERROR_SYSTEM|2, "waitpid failed");
					return 1;
				}
				if (!WIFEXITED(i) || (exitstatus = WEXITSTATUS(i)) > 1)
				{
					error(ERROR_ERROR|2, "child process exited abnormally");
					return 1;
				}
				if (exitstatus == 0)
					break;	/* yay :) */
				extra_bytes++;
				if (extra_bytes > 256)
				{
					error(ERROR_ERROR|2, "giving up");
					return 1;
				}
			}
		}
		sfprintf(sfstdout,
			"#define ARG_EXTRA_BYTES\t%d\t/* extra bytes per argument for arguments list */\n",
			extra_bytes);
		return 0;
	}
}end fail{
	echo "#define ARG_EXTRA_BYTES	16	/* BUG: test failed; assuming 16 */"
}end