overhaul tmpfile, tmpnam, and tempnam functions

these all now use the shared __randname function internally, rather
than duplicating logic for producing a random name. incorrect usage of
the access syscall (which works with real uid/gid, not effective) has
been removed, along with unnecessary heavy dependencies like snprintf.

src/stdio/tempnam.c

 #include <stdio.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <limits.h>
 #include <string.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <unistd.h>
-#include <time.h>
-#include "libc.h"
-#include "atomic.h"
+#include "syscall.h"
 
 #define MAXTRIES 100
 
+char *__randname(char *);
+
 char *tempnam(const char *dir, const char *pfx)
 {
-	static int index;
-	char *s;
-	struct timespec ts;
-	int pid = getpid();
-	size_t l;
-	int n;
-	int try=0;
+	char s[PATH_MAX];
+	size_t l, dl, pl;
+	int try;
+	int r;
 
 	if (!dir) dir = P_tmpdir;
 	if (!pfx) pfx = "temp";
 
-	if (access(dir, R_OK|W_OK|X_OK) != 0)
-		return NULL;
-
-	l = strlen(dir) + 1 + strlen(pfx) + 3*(sizeof(int)*3+2) + 1;
-	s = malloc(l);
-	if (!s) return s;
+	dl = strlen(dir);
+	pl = strlen(pfx);
+	l = dl + 1 + pl + 1 + 6;
 
-	do {
-		clock_gettime(CLOCK_REALTIME, &ts);
-		n = ts.tv_nsec ^ (uintptr_t)&s ^ (uintptr_t)s;
-		snprintf(s, l, "%s/%s-%d-%d-%x", dir, pfx, pid, a_fetch_add(&index, 1), n);
-	} while (!access(s, F_OK) && try++<MAXTRIES);
-	if (try>=MAXTRIES) {
-		free(s);
+	if (l >= PATH_MAX) {
+		errno = ENAMETOOLONG;
 		return 0;
 	}
-	return s;
+
+	memcpy(s, dir, dl);
+	s[dl] = '/';
+	memcpy(s+dl+1, pfx, pl);
+	s[dl+1+pl] = '_';
+
+	for (try=0; try<MAXTRIES; try++) {
+		__randname(s+l-6);
+		r = __syscall(SYS_lstat, s, &(struct stat){0});
+		if (r == -ENOENT) return strdup(s);
+	}
+	return 0;
 }

src/stdio/tmpfile.c

 #include <stdio.h>
 #include <fcntl.h>
-#include <unistd.h>
 #include "stdio_impl.h"
 
 #define MAXTRIES 100
 
+char *__randname(char *);
+
 FILE *tmpfile(void)
 {
-	char buf[L_tmpnam], *s;
+	char s[] = "/tmp/tmpfile_XXXXXX";
 	int fd;
 	FILE *f;
 	int try;
 	for (try=0; try<MAXTRIES; try++) {
-		s = tmpnam(buf);
-		if (!s) return 0;
+		__randname(s+13);
 		fd = sys_open(s, O_RDWR|O_CREAT|O_EXCL, 0600);
 		if (fd >= 0) {
 			f = __fdopen(fd, "w+");

src/stdio/tmpnam.c

 #include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <unistd.h>
-#include <time.h>
-#include "libc.h"
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/stat.h>
 #include "syscall.h"
-#include "atomic.h"
 
 #define MAXTRIES 100
 
-char *tmpnam(char *s)
-{
-	static int index;
-	static char s2[L_tmpnam];
-	struct timespec ts;
-	int try = 0;
-	unsigned n;
-
-	if (!s) s = s2;
+char *__randname(char *);
 
-	if (__syscall(SYS_access, P_tmpdir, R_OK|W_OK|X_OK) != 0)
-		return NULL;
-
-	do {
-		__syscall(SYS_clock_gettime, CLOCK_REALTIME, &ts, 0);
-		n = ts.tv_nsec ^ (uintptr_t)&s ^ (uintptr_t)s;
-		snprintf(s, L_tmpnam, "/tmp/t%x-%x", a_fetch_add(&index, 1), n);
-	} while (!__syscall(SYS_access, s, F_OK) && try++<MAXTRIES);
-	return try>=MAXTRIES ? 0 : s;
+char *tmpnam(char *buf)
+{
+	static char internal[L_tmpnam];
+	char s[] = "/tmp/tmpnam_XXXXXX";
+	int try;
+	int r;
+	for (try=0; try<MAXTRIES; try++) {
+		__randname(s+12);
+		r = __syscall(SYS_lstat, s, &(struct stat){0});
+		if (r == -ENOENT) return strcpy(buf ? buf : internal, s);
+	}
+	return 0;
 }