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fstat: add test and documentation for an edge case. 

The fstatat behaviour when the target is a dangling symlink is different
if flags contains AT_SYMLINK_NOFOLLOW or not.
Add a test for this and document it.
This commit is contained in:
Matteo Croce 2025-06-24 18:40:13 +02:00 committed by Adhemerval Zanella
parent 652c36b3ea
commit 521b4d6c4d
2 changed files with 19 additions and 3 deletions
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17
io/tst-stat.c
View File

@ -62,12 +62,23 @@ fstatat_check (int fd, const char *path, struct stat *st)
TEST_COMPARE (fstatat (fd, path, st, 0), 0);
}
static void
fstatat_link (const char *path, struct stat *st)
{
TEST_COMPARE (fstatat (AT_FDCWD, path, st, 0), -1);
TEST_COMPARE (errno, ENOENT);
TEST_COMPARE (fstatat (AT_FDCWD, path, st, AT_SYMLINK_NOFOLLOW), 0);
TEST_COMPARE (!S_ISLNK(st->st_mode), 0);
}
typedef void (*test_t)(int, const char *path, struct stat *);
static int
do_test (void)
{
char *path;
const char *linkame = "tst-fstat.linkname";
int fd = create_temp_file ("tst-fstat.", &path);
TEST_VERIFY_EXIT (fd >= 0);
support_write_file_string (path, "abc");
@ -81,13 +92,13 @@ do_test (void)
printf ("warning: timestamp with nanoseconds not supported\n");
struct statx stx;
struct stat st;
TEST_COMPARE (statx (fd, path, 0, STATX_BASIC_STATS, &stx), 0);
test_t tests[] = { stat_check, lstat_check, fstat_check, fstatat_check };
for (int i = 0; i < array_length (tests); i++)
{
struct stat st;
tests[i](fd, path, &st);
TEST_COMPARE (stx.stx_dev_major, major (st.st_dev));
@ -111,6 +122,10 @@ do_test (void)
}
}
TEST_COMPARE (symlink ("tst-fstat.target", linkame), 0);
add_temp_file (linkame);
fstatat_link (linkame, &st);
return 0;
}

5
manual/filesys.texi
View File

@ -2400,8 +2400,9 @@ The descriptor @var{filedes} is not associated with a directory, and
@var{filename} is a relative file name.
@item ENOENT
The file named by @var{filename} does not exist, or @var{filename} is an
empty string and @var{flags} does not contain @code{AT_EMPTY_PATH}.
The file named by @var{filename} does not exist, it's a dangling symbolic link
and @var{flags} does not contain @code{AT_SYMLINK_NOFOLLOW}, or @var{filename}
is an empty string and @var{flags} does not contain @code{AT_EMPTY_PATH}.
@end table
When the sources are compiled with @code{_FILE_OFFSET_BITS == 64} this