Subject: Re: [PATCH] clean: use warning_errno() when appropriate

From: Junio C Hamano <[email-masked]>
Date: Mon, 13 Feb 2017 10:34:06 -0800

Nguyễn Thái Ngọc Duy  <[email-masked]> writes:

> All these warning() calls are preceded by a system call. Report the
> actual error to help the user understand why we fail to remove
> something.

I think this patch is probably correct in the current code, but I
say this only after following what quote_path_relative() and
relative_path() that is called from it.  These warnings are preceded
by a call to a system library function, but it is not apparent that
they are immediately preceded without anything else that could have
failed in between.

    Side note.  There are many calls into strbuf API in these two
    functions.  Any calls to xmalloc() and friends made by strbuf
    functions may see ENOMEM from underlying malloc() and recover by
    releasing cached resources, by which time the original errno is
    unrecoverable.  So the above "probably correct" is not strictly
    true.

If we care deeply enough that we want to reliably show the errno we
got from the preceding call to a system library function even after
whatever comes in between, I think you'd need the usual saved_errno
trick.  Is that worth it?---I do not offhand have an opinion.

> Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
> ---
>  builtin/clean.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/builtin/clean.c b/builtin/clean.c
> index d6bc3aaaea..dc1168747e 100644
> --- a/builtin/clean.c
> +++ b/builtin/clean.c
> @@ -175,7 +175,7 @@ static int remove_dirs(struct strbuf *path, const char *prefix, int force_flag,
>  		res = dry_run ? 0 : rmdir(path->buf);
>  		if (res) {
>  			quote_path_relative(path->buf, prefix, &quoted);
> -			warning(_(msg_warn_remove_failed), quoted.buf);
> +			warning_errno(_(msg_warn_remove_failed), quoted.buf);
>  			*dir_gone = 0;
>  		}
>  		return res;
> @@ -209,7 +209,7 @@ static int remove_dirs(struct strbuf *path, const char *prefix, int force_flag,
>  				string_list_append(&dels, quoted.buf);
>  			} else {
>  				quote_path_relative(path->buf, prefix, &quoted);
> -				warning(_(msg_warn_remove_failed), quoted.buf);
> +				warning_errno(_(msg_warn_remove_failed), quoted.buf);
>  				*dir_gone = 0;
>  				ret = 1;
>  			}
> @@ -231,7 +231,7 @@ static int remove_dirs(struct strbuf *path, const char *prefix, int force_flag,
>  			*dir_gone = 1;
>  		else {
>  			quote_path_relative(path->buf, prefix, &quoted);
> -			warning(_(msg_warn_remove_failed), quoted.buf);
> +			warning_errno(_(msg_warn_remove_failed), quoted.buf);
>  			*dir_gone = 0;
>  			ret = 1;
>  		}
> @@ -982,7 +982,7 @@ int cmd_clean(int argc, const char **argv, const char *prefix)
>  			res = dry_run ? 0 : unlink(abs_path.buf);
>  			if (res) {
>  				qname = quote_path_relative(item->string, NULL, &buf);
> -				warning(_(msg_warn_remove_failed), qname);
> +				warning_errno(_(msg_warn_remove_failed), qname);
>  				errors++;
>  			} else if (!quiet) {
>  				qname = quote_path_relative(item->string, NULL, &buf);