mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Dominique MARTINET <dominique.martinet@atmark-techno.com>
To: musl@lists.openwall.com
Cc: Rich Felker <dalias@libc.org>, Ismael Luceno <ismael@iodev.co.uk>
Subject: Re: [musl] [PATCH v3 2/2] nftw: implement FTW_ACTIONRETVAL (GNU extension)
Date: Mon, 24 Jan 2022 09:47:33 +0900	[thread overview]
Message-ID: <Ye33JWzA/+qZRQUF@atmark-techno.com> (raw)
In-Reply-To: <20220123155955.16484-3-ismael@iodev.co.uk>

This didn't get much traction when I submitted one last year:
https://www.openwall.com/lists/musl/2021/03/26/1
(and there were at least a couple other occurences I could find at the
time)
But given it keeps getting resubmitted I assume we can say that confirms
there's demand for it?

Ismael Luceno wrote on Sun, Jan 23, 2022 at 04:59:55PM +0100:
> diff --git a/include/ftw.h b/include/ftw.h
> index b15c062a8389..2e77dc76e11b 100644
> --- a/include/ftw.h
> +++ b/include/ftw.h
> @@ -21,6 +21,13 @@ extern "C" {
>  #define FTW_CHDIR 4
>  #define FTW_DEPTH 8
>  
> +#define FTW_ACTIONRETVAL  16
> +/* return values for callback */
> +#define FTW_CONTINUE	  0
> +#define FTW_STOP          1
> +#define FTW_SKIP_SUBTREE  2
> +#define FTW_SKIP_SIBLINGS 3

FWIW since this is a GNU extension I only had defined these in a
#ifdef _GNU_SOURCE block, but this had the ugly side effect of having to
redefine SUBTREE/SIBLINGS in the .c so I'm not sure which is better.

> +
>  struct FTW {
>  	int base;
>  	int level;
> diff --git a/src/misc/nftw.c b/src/misc/nftw.c
> index 7569a657e54e..382169f66b8b 100644
> --- a/src/misc/nftw.c
> +++ b/src/misc/nftw.c
> @@ -26,7 +26,7 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
>  	struct stat st;
>  	struct history new;
>  	int type;
> -	int r;
> +	int r, r2;
>  	int dfd;
>  	int err;
>  	struct FTW lev;
> @@ -72,12 +72,19 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
>  		if (!fd_limit) close(dfd);
>  	}
>  
> -	if (!(flags & FTW_DEPTH) && (r=fn(path, &st, type, &lev)))
> -		return r;
> +	r = 0;
> +	if (!(flags & FTW_DEPTH) && (r=fn(path, &st, type, &lev))) {
> +		if ((flags & FTW_ACTIONRETVAL)) {
> +			if (r == FTW_STOP) return FTW_STOP;
> +			if (r == FTW_SKIP_SUBTREE) return 0;
> +			/* other values are saved for when returning */

Hm, I'd naively think you would want to return immediately the other
values as well, so the else below is wrong?
But I didn't take long enough to check what e.g. a SKIP_SIBLINGS would
mean here, the construction just looks a bit odd to me.

> +		} else
> +			return r;
> +	}
>  
>  	for (; h; h = h->chain)
>  		if (h->dev == st.st_dev && h->ino == st.st_ino)
> -			return 0;
> +			return r;
>  
>  	if ((type == FTW_D || type == FTW_DP) && fd_limit) {
>  		if (dfd < 0) {
> @@ -107,9 +114,12 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
>  				}
>  				path[j]='/';
>  				strcpy(path+j+1, de->d_name);
> -				if ((r=do_nftw(path, fn, fd_limit-1, flags, &new))) {
> +				if ((r2=do_nftw(path, fn, fd_limit-1, flags, &new))) {
> +					if ((flags & FTW_ACTIONRETVAL)
> +					    && r2 == FTW_SKIP_SIBLINGS)
> +						break;
>  					closedir(d);
> -					return r;
> +					return r2;
>  				}
>  			}
>  			closedir(d);
> @@ -120,10 +130,13 @@ static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int,
>  	}
>  
>  	path[l] = 0;
> -	if ((flags & FTW_DEPTH) && (r=fn(path, &st, type, &lev)))
> -		return r;
> -
> -	return 0;
> +	if (flags & FTW_DEPTH) {
> +		r = fn(path, &st, type, &lev);
> +		/* ignore FTW_SKIP_SUBTREE (too late), the caller is broken */
> +		if ((flags & FTW_ACTIONRETVAL) && r == FTW_SKIP_SUBTREE)
> +			return 0;

IIRC the glibc implementation also ignores FTW_SKIP_SIBLINGS in that
case (nftw returns 0), I'm not sure how much of a 1-to-1 implementation
we want -- I had implemented my version through a black-box approach
with a client exercising all kind of different code paths as for a gnu
extension I'd assume glibc to be the reference.

I haven't taken the time to rerun that comparison (the test client is in
a comment in my patch), but I probably will if this looks like it would
get merged unless someone else did.

> +	}
> +	return r;
>  }
>  
>  int nftw(const char *path, int (*fn)(const char *, const struct stat *, int, struct FTW *), int fd_limit, int flags)

-- 
Dominique

  reply	other threads:[~2022-01-24  0:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-23 15:59 [musl] [PATCH v3 0/2] nftw: Implement FTW_CHDIR and FTW_ACTIONRETVAL Ismael Luceno
2022-01-23 15:59 ` [musl] [PATCH v3 1/2] nftw: implement FTW_CHDIR Ismael Luceno
2022-05-12 13:00   ` Rich Felker
2022-01-23 15:59 ` [musl] [PATCH v3 2/2] nftw: implement FTW_ACTIONRETVAL (GNU extension) Ismael Luceno
2022-01-24  0:47   ` Dominique MARTINET [this message]
2022-01-24 19:53     ` Ismael Luceno
2022-03-09  4:37       ` Dominique MARTINET
2022-03-09 11:41         ` Rich Felker
2022-04-28  2:02           ` Dominique MARTINET
2022-01-24 22:13 ` [musl] [PATCH v3 0/2] nftw: Implement FTW_CHDIR and FTW_ACTIONRETVAL Rich Felker

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Ye33JWzA/+qZRQUF@atmark-techno.com \
    --to=dominique.martinet@atmark-techno.com \
    --cc=dalias@libc.org \
    --cc=ismael@iodev.co.uk \
    --cc=musl@lists.openwall.com \
    --subject='Re: [musl] [PATCH v3 2/2] nftw: implement FTW_ACTIONRETVAL (GNU extension)' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Code repositories for project(s) associated with this inbox:

	https://git.vuxu.org/mirror/musl/

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).