musl/src/stdio/tmpnam.c
Rich Felker 9a93749555 drop use of stat operation in temporary file name generation
this change serves two purposes:

1. it eliminates one of the few remaining uses of the kernel stat
structure which will not be present in future archs, avoiding the need
for growing ifdef logic here.

2. it potentially makes the operations less expensive when the
candidate exists as a non-symlink by avoiding the need to read the
inode (assuming the directory tables suffice to distinguish symlinks).

this uses the idiom I discovered while rewriting realpath for commit
29ff7599a4 of being able to use the
readlink operation as an inexpensive probe for file existence that
doesn't following symlinks.
2022-05-01 23:25:21 -04:00

27 lines
553 B
C

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <string.h>
#include <stdlib.h>
#include "syscall.h"
#define MAXTRIES 100
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);
#ifdef SYS_readlink
r = __syscall(SYS_readlink, s, (char[1]){0}, 1);
#else
r = __syscall(SYS_readlinkat, AT_FDCWD, s, (char[1]){0}, 1);
#endif
if (r == -ENOENT) return strcpy(buf ? buf : internal, s);
}
return 0;
}