Guix-Upstream: https://lists.gnu.org/archive/html/guile-devel/2021-11/msg00005.html
From: Maxime Devos
Subject: [PATCH v2 02/14]
=?UTF-8?q?Allow=20file=20ports=20in=20=E2=80=98r?=
=?UTF-8?q?eadlink=E2=80=99.?=
Date: Tue, 16 Nov 2021 11:06:25 +0000
Message-Id: <20211116110637.125579-3-maximedevos@telenet.be>
In-Reply-To: <20211116110637.125579-1-maximedevos@telenet.be>
References: <175c3a6572e832d84927937b309a3095cadf5702.camel@telenet.be>
<20211116110637.125579-1-maximedevos@telenet.be>
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* configure.ac: Detect whether ‘readlinkat’ is defined.
* libguile/filesys.c (scm_readlink): Support file ports
when ‘readlinkat’ exists.
(scm_init_filesys): Provide ‘chdir-ports’ when it exists.
* doc/ref/posix.texi (File System): Document it.
* test-suite/tests/filesys.test ("readlink"): Test it.
---
configure.ac | 2 +-
doc/ref/posix.texi | 9 ++++--
libguile/filesys.c | 52 +++++++++++++++++++++++------
test-suite/tests/filesys.test | 61 +++++++++++++++++++++++++++++++++++
4 files changed, 112 insertions(+), 12 deletions(-)
diff --git a/configure.ac b/configure.ac
index b7e4663f7..4888f880d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -484,7 +484,7 @@ AC_CHECK_HEADERS([assert.h crt_externs.h])
# sendfile - non-POSIX, found in glibc
#
AC_CHECK_FUNCS([DINFINITY DQNAN cexp chsize clog clog10 ctermid \
- fesetround ftime ftruncate fchown fchmod fchdir \
+ fesetround ftime ftruncate fchown fchmod fchdir readlinkat \
getcwd geteuid getsid \
gettimeofday getuid getgid gmtime_r ioctl lstat mkdir mkdtemp mknod \
nice readlink rename rmdir setegid seteuid \
diff --git a/doc/ref/posix.texi b/doc/ref/posix.texi
index 7555f9319..cd23240c4 100644
--- a/doc/ref/posix.texi
+++ b/doc/ref/posix.texi
@@ -757,8 +757,13 @@ file it points to. @var{path} must be a string.
@deffn {Scheme Procedure} readlink path
@deffnx {C Function} scm_readlink (path)
-Return the value of the symbolic link named by @var{path} (a
-string), i.e., the file that the link points to.
+Return the value of the symbolic link named by @var{path} (a string, or
+a port if supported by the system), i.e., the file that the link points
+to.
+
+To read a symbolic link represented by a port, the symbolic link must
+have been opened with the @code{O_NOFOLLOW} and @code{O_PATH} flags.
+@code{(provided? 'readlink-port)} reports whether ports are supported.
@end deffn
@findex fchown
diff --git a/libguile/filesys.c b/libguile/filesys.c
index 2a9c36a12..c5bedec07 100644
--- a/libguile/filesys.c
+++ b/libguile/filesys.c
@@ -1045,10 +1045,30 @@ SCM_DEFINE (scm_symlink, "symlink", 2, 0, 0,
#undef FUNC_NAME
#endif /* HAVE_SYMLINK */
-SCM_DEFINE (scm_readlink, "readlink", 1, 0, 0,
+/* Static helper function for choosing between readlink
+ and readlinkat. */
+static int
+do_readlink (int fd, const char *c_path, char *buf, size_t size)
+{
+#ifdef HAVE_READLINKAT
+ if (fd != -1)
+ return readlinkat (fd, c_path, buf, size);
+#else
+ (void) fd;
+#endif
+ return readlink (c_path, buf, size);
+}
+
+SCM_DEFINE (scm_readlink, "readlink", 1, 0, 0,
(SCM path),
- "Return the value of the symbolic link named by @var{path} (a\n"
- "string), i.e., the file that the link points to.")
+ "Return the value of the symbolic link named by @var{path} (a\n"
+ "string, or a port if supported by the system),\n"
+ "i.e., the file that the link points to.\n"
+ "To read a symbolic link represented by a port, the symbolic\n"
+ "link must have been opened with the @code{O_NOFOLLOW} and\n"
+ "@code{O_PATH} flags."
+ "@code{(provided? 'readlink-port)} reports whether ports are\n"
+ "supported.")
#define FUNC_NAME s_scm_readlink
{
int rv;
@@ -1056,20 +1076,31 @@ SCM_DEFINE (scm_readlink, "readlink", 1, 0, 0,
char *buf;
SCM result;
char *c_path;
-
- scm_dynwind_begin (0);
-
- c_path = scm_to_locale_string (path);
- scm_dynwind_free (c_path);
+ int fdes;
+ scm_dynwind_begin (0);
+#ifdef HAVE_READLINKAT
+ if (SCM_OPFPORTP (path))
+ {
+ c_path = "";
+ fdes = SCM_FPORT_FDES (path);
+ }
+ else
+#endif
+ {
+ fdes = -1;
+ c_path = scm_to_locale_string (path);
+ scm_dynwind_free (c_path);
+ }
buf = scm_malloc (size);
- while ((rv = readlink (c_path, buf, size)) == size)
+ while ((rv = do_readlink (fdes, c_path, buf, size)) == size)
{
free (buf);
size *= 2;
buf = scm_malloc (size);
}
+ scm_remember_upto_here_1 (path);
if (rv == -1)
{
int save_errno = errno;
@@ -2086,6 +2117,9 @@ scm_init_filesys ()
#ifdef HAVE_FCHDIR
scm_add_feature("chdir-port");
#endif
+#ifdef HAVE_READLINKAT
+ scm_add_feature("readlink-port");
+#endif
#include "filesys.x"
}
diff --git a/test-suite/tests/filesys.test b/test-suite/tests/filesys.test
index 6b09a2ba0..7feb3492f 100644
--- a/test-suite/tests/filesys.test
+++ b/test-suite/tests/filesys.test
@@ -306,3 +306,64 @@
(pass-if-exception "non-file port" exception:wrong-type-arg
(chdir (open-input-string ""))))
+
+(with-test-prefix "readlink"
+ (false-if-exception (delete-file (test-symlink)))
+ (false-if-exception (delete-file (test-file)))
+ (call-with-output-file (test-file)
+ (lambda (port)
+ (display "hello" port)))
+ (if (not (false-if-exception
+ (begin (symlink (test-file) (test-symlink)) #t)))
+ (display "cannot create symlink, some readlink tests skipped\n")
+ (let ()
+ (pass-if-equal "file name of symlink" (test-file)
+ (readlink (test-symlink)))
+
+ (pass-if-equal "port representing a symlink" (test-file)
+ (let ()
+ (unless (and (provided? 'readlink-port)
+ (defined? 'O_NOFOLLOW)
+ (defined? 'O_PATH)
+ (not (= 0 O_NOFOLLOW))
+ (not (= 0 O_PATH)))
+ (throw 'unsupported))
+ (define port (open (test-symlink) (logior O_NOFOLLOW O_PATH)))
+ (define points-to (false-if-exception (readlink port)))
+ (close-port port)
+ points-to))
+
+ (pass-if-exception "not a port or file name" exception:wrong-type-arg
+ (readlink '(stuff)))))
+
+ (pass-if-equal "port representing a regular file" EINVAL
+ (call-with-input-file (test-file)
+ (lambda (port)
+ (unless (provided? 'readlink-port)
+ (throw 'unsupported))
+ (catch 'system-error
+ (lambda ()
+ (readlink port)
+ (close-port port) ; should be unreachable
+ #f)
+ (lambda args
+ (close-port port)
+ ;; At least Linux 5.10.46 returns ENOENT instead of EINVAL.
+ ;; Possibly surprising, but it is documented in some man
+ ;; pages and it doesn't appear to be an accident:
+ ;; .
+ (define error (system-error-errno args))
+ (if (= error ENOENT)
+ EINVAL
+ error))))))
+
+ (pass-if-exception "non-file port" exception:wrong-type-arg
+ (readlink (open-input-string "")))
+
+ (pass-if-exception "closed port" exception:wrong-type-arg
+ (let ((port (open-file (test-file) "r")))
+ (close-port port)
+ (readlink port)))
+
+ (false-if-exception (delete-file (test-symlink)))
+ (false-if-exception (delete-file (test-file))))
--
2.30.2