[Toybox] ls -l broken

[enh]

[PATCH] dirtree: fix 0b2cfcb8fdea9673f3c2e0940f1b16d5825e16ea.

0b2cfcb8fdea9673f3c2e0940f1b16d5825e16ea broke `ls -l` on files that
don't exist.

We didn't spot this because the corresponding ls test (which did exist)
had accidentally been mangled in a couple of ways.

This patch fixes the test (and extends it to differentiate between a
couple of possible ways it can go wrong), and fixes the broken path in
dirtree_add_node.

Bug: http://b/144698492
---
 lib/dirtree.c | 14 +++++++-------
 tests/ls.test |  5 +++--
 2 files changed, 10 insertions(+), 9 deletions(-)

On Wed, Nov 20, 2019 at 2:04 PM enh <enh at google.com> wrote:
>
> this change broke `ls -l` for non-existent arguments:
>
> /tmp/toybox-dirtree$ ./toybox ls -l /asd
> b--------T 140728898420758 1964107300 476192747 2935, 304972
> 1969-12-31 16:00 /asd
> /tmp/toybox-dirtree$ git revert 0b2cfcb8fdea9673f3c2e0940f1b16d5825e16ea
> [master f83f87fa] Revert "Let "find -L -type -l" find dangling symlinks."
>  1 file changed, 6 insertions(+), 12 deletions(-)
> /tmp/toybox-dirtree$ make
> scripts/make.sh
> Generate headers from toys/*/*.c...
> Library probe...........
> Make generated/config.h from .config.
> Compile toybox......
> /tmp/toybox-dirtree$ ./toybox ls -l /asd
> ls: /asd: No such file or directory
> /tmp/toybox-dirtree$ ./toybox ls -l /asd
> ls: /asd: No such file or directory
> /tmp/toybox-dirtree$ ./toybox ls -l /asd
> ls: /asd: No such file or directory
>
>
>
> commit 0b2cfcb8fdea9673f3c2e0940f1b16d5825e16ea
> Author: Rob Landley <rob at landley.net>
> Date:   Tue Oct 29 10:59:46 2019 -0500
>
>     Let "find -L -type -l" find dangling symlinks.
>
> diff --git a/lib/dirtree.c b/lib/dirtree.c
> index df38b257..beaafd59 100644
> --- a/lib/dirtree.c
> +++ b/lib/dirtree.c
> @@ -32,12 +32,18 @@ struct dirtree *dirtree_add_node(struct dirtree *parent, cha
> r *name, int flags)
>    int len = 0, linklen = 0, statless = 0;
>
>    if (name) {
> -    // open code this because haven't got node to call dirtree_parentfd() on ye
> t
> -    int fd = parent ? parent->dirfd : AT_FDCWD;
> -
> -    if (fstatat(fd, name, &st,AT_SYMLINK_NOFOLLOW*!(flags&DIRTREE_SYMFOLLOW)))
> {
> -      if (flags&DIRTREE_STATLESS) statless++;
> -      else goto error;
> +    // open code fd = because haven't got node to call dirtree_parentfd() on ye
> t
> +    int fd = parent ? parent->dirfd : AT_FDCWD,
> +      sym = AT_SYMLINK_NOFOLLOW*!(flags&DIRTREE_SYMFOLLOW);
> +
> +    // stat dangling symlinks
> +    if (fstatat(fd, name, &st, sym)) {
> +      if (errno != ENOENT
> +        || (!sym && fstatat(fd, name, &st, AT_SYMLINK_NOFOLLOW)))
> +      {
> +        if (flags&DIRTREE_STATLESS) statless++;
> +        else goto error;
> +      }
>      }
>      if (S_ISLNK(st.st_mode)) {
>        if (0>(linklen = readlinkat(fd, name, libbuf, 4095))) goto error;
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