Mercurial > hg > octave-nkf > gnulib-hg
changeset 12060:95a12a00ea4f
readlink: document portability issue with symlink length
Per comments in areadlink, ERANGE on a too-small buffer is
expected on some platforms; making the readlink module guarantee
GNU behavior of truncated contents is counter-productive, since
we would be duplicating areadlink to learn a-priori how large to
make the buffer, and since truncated contents are not as useful.
* doc/posix-functions/lstat.texi (lstat): Mention that some file
systems have bogus st_size on symlinks, and mention the
areadlink-with-size module.
* doc/posix-functions/fstatat.texi (fstatat): Likewise.
* doc/posix-functions/readlink.texi (readlink): Mention the
areadlink module, and ERANGE failure.
* doc/posix-functions/readlinkat.texi (readlinkat): Likewise.
* tests/test-readlink.c (main): Relax test for AIX, HP-UX.
Signed-off-by: Eric Blake <ebb9@byu.net>
author | Eric Blake <ebb9@byu.net> |
---|---|
date | Mon, 21 Sep 2009 14:40:20 -0600 |
parents | 6babf16a67dd |
children | c47da311af77 |
files | ChangeLog doc/posix-functions/fstatat.texi doc/posix-functions/lstat.texi doc/posix-functions/readlink.texi doc/posix-functions/readlinkat.texi tests/test-readlink.c |
diffstat | 6 files changed, 49 insertions(+), 4 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,15 @@ 2009-09-23 Eric Blake <ebb9@byu.net> + readlink: document portability issue with symlink length + * doc/posix-functions/lstat.texi (lstat): Mention that some file + systems have bogus st_size on symlinks, and mention the + areadlink-with-size module. + * doc/posix-functions/fstatat.texi (fstatat): Likewise. + * doc/posix-functions/readlink.texi (readlink): Mention the + areadlink module, and ERANGE failure. + * doc/posix-functions/readlinkat.texi (readlinkat): Likewise. + * tests/test-readlink.c (main): Relax test for AIX, HP-UX. + readlink: fix Solaris 9 bug with trailing slash * lib/readlink.c (rpl_readlink): Work around trailing slash bug. * m4/readlink.m4 (gl_FUNC_READLINK): Detect the bug.
--- a/doc/posix-functions/fstatat.texi +++ b/doc/posix-functions/fstatat.texi @@ -31,4 +31,8 @@ GB. The fix is to use the @code{AC_SYS_LARGEFILE} macro. @item On Windows platforms (excluding Cygwin), @code{st_ino} is always 0. +@item +On some filesystems, @code{st_size} contains bogus information for +symlinks; use the gnulib module areadlink-with-size for a better way +to get symlink contents. @end itemize
--- a/doc/posix-functions/lstat.texi +++ b/doc/posix-functions/lstat.texi @@ -35,4 +35,8 @@ expressions such as @code{(islnk ? lstat : stat) (name, buf)} are not portable, and should instead be written @code{islnk ? lstat (name, buf) : stat (name, buf)}. +@item +On some filesystems, @code{st_size} contains bogus information for +symlinks; use the gnulib module areadlink-with-size for a better way +to get symlink contents. @end itemize
--- a/doc/posix-functions/readlink.texi +++ b/doc/posix-functions/readlink.texi @@ -31,4 +31,12 @@ When @code{readlink} is called on a file that is not a symbolic link: Irix may set @code{errno} to @code{ENXIO} instead of @code{EINVAL}. Cygwin may set errno to @code{EACCES} instead of @code{EINVAL}. +@item +Symlink contents do not always have a trailing null byte, and there is +no indication if symlink contents were truncated if the return value +matches the length. Furthermore, AIX 5.1 and HP-UX 11 set +@code{errno} to @code{ERANGE} rather than returning truncated +contents, and Linux sets @code{errno} to @code{EINVAL} if the +requested length is zero. Use the gnulib module areadlink for +improved ability to read symlink contents. @end itemize
--- a/doc/posix-functions/readlinkat.texi +++ b/doc/posix-functions/readlinkat.texi @@ -28,4 +28,12 @@ When @code{readlink} is called on a file that is not a symbolic link: Irix may set @code{errno} to @code{ENXIO} instead of @code{EINVAL}. Cygwin may set errno to @code{EACCES} instead of @code{EINVAL}. +@item +Symlink contents do not always have a trailing null byte, and there is +no indication if symlink contents were truncated if the return value +matches the length. Furthermore, AIX 5.1 and HP-UX 11 set +@code{errno} to @code{ERANGE} rather than returning truncated +contents, and Linux sets @code{errno} to @code{EINVAL} if the +requested length is zero. Use the gnulib module areadlink for +improved ability to read symlink contents. @end itemize
--- a/tests/test-readlink.c +++ b/tests/test-readlink.c @@ -97,10 +97,21 @@ { size_t len = strlen (BASE "dir"); /* When passing too small of a buffer, expect the truncated - length. However, a size of 0 is not portable enough to - test. */ - ASSERT (readlink (BASE "link", buf, 1) == 1); - ASSERT (buf[0] == BASE[0]); + length, or an ERANGE failure. However, a size of 0 is not + portable enough to test. */ + ssize_t result; + errno = 0; + result = readlink (BASE "link", buf, 1); + if (result == -1) + { + ASSERT (errno == ERANGE); + ASSERT (buf[0] == (char) 0xff); + } + else + { + ASSERT (result == 1); + ASSERT (buf[0] == BASE[0]); + } ASSERT (buf[1] == (char) 0xff); ASSERT (readlink (BASE "link", buf, len) == len); ASSERT (strncmp (buf, BASE "dir", len) == 0);