Subject: Re: [PATCH 2/2] Fix callsites of real_pathdup() that wanted it to die on error

From: Brandon Williams <[email-masked]>
Date: Wed, 8 Mar 2017 10:38:40 -0800

On 03/08, René Scharfe wrote:
> Am 08.03.2017 um 16:43 schrieb Johannes Schindelin:
> > In 4ac9006f832 (real_path: have callers use real_pathdup and
> > strbuf_realpath, 2016-12-12), we changed the xstrdup(real_path())
> > pattern to use real_pathdup() directly.
> > 
> > The only problem with this change is that real_path() calls
> > strbuf_realpath() with die_on_error = 1 while real_pathdup() calls it
> > with die_on_error = 0. Meaning that in cases where real_path() causes
> > Git to die() with an error message, real_pathdup() is silent and returns
> > NULL instead.
> > 
> > The callers, however, are ill-prepared for that change, as they expect
> > the return value to be non-NULL.
> > 
> > This patch fixes that by extending real_pathdup()'s signature to accept
> > the die_on_error flag and simply pass it through to strbuf_realpath(),
> > and then adjust all callers after a careful audit whether they would
> > handle NULLs well.
> > 
> > Note: this fix not only prevents NULL pointer accesses, but it also
> > reintroduces the error messages that were lost with the change to
> > real_pathdup().
> > 
> > Signed-off-by: Johannes Schindelin <[email-masked]>
> > ---
> >  abspath.c            |  4 ++--
> >  builtin/init-db.c    |  6 +++---
> >  cache.h              |  2 +-
> >  dir.c                |  4 ++--
> >  environment.c        |  2 +-
> >  setup.c              |  4 ++--
> >  submodule.c          | 10 +++++-----
> >  t/t1501-work-tree.sh |  2 +-
> >  worktree.c           |  2 +-
> >  9 files changed, 18 insertions(+), 18 deletions(-)
> > 
> > diff --git a/abspath.c b/abspath.c
> > index 2f0c26e0e2c..b02e068aa34 100644
> > --- a/abspath.c
> > +++ b/abspath.c
> > @@ -214,12 +214,12 @@ const char *real_path_if_valid(const char *path)
> >  	return strbuf_realpath(&realpath, path, 0);
> >  }
> >  
> > -char *real_pathdup(const char *path)
> > +char *real_pathdup(const char *path, int die_on_error)
> 
> Adding a gentle variant (with the current implementation) and making
> real_pathdup() die on error would be nicer, as it doesn't require
> callers to pass magic flag values.  Most cases use the dying variant,
> so such a patch would have to touch less places:

I agree with Junio and Rene that a gentle version would make the api
slightly nicer (and more consistant with some of the other api's we have
in git).

This is exactly what I should have done back when I originally made the
change.  Sorry for missing this!
> ---
>  abspath.c            | 7 +++++++
>  cache.h              | 1 +
>  setup.c              | 2 +-
>  t/t1501-work-tree.sh | 2 +-
>  4 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/abspath.c b/abspath.c
> index 2f0c26e0e2..f3fcff8b1b 100644
> --- a/abspath.c
> +++ b/abspath.c
> @@ -217,6 +217,13 @@ const char *real_path_if_valid(const char *path)
>  char *real_pathdup(const char *path)
>  {
>  	struct strbuf realpath = STRBUF_INIT;
> +	strbuf_realpath(&realpath, path, 1);
> +	return strbuf_detach(&realpath, NULL);
> +}
> +
> +char *real_pathdup_gently(const char *path)
> +{
> +	struct strbuf realpath = STRBUF_INIT;
>  	char *retval = NULL;
>  
>  	if (strbuf_realpath(&realpath, path, 0))
> diff --git a/cache.h b/cache.h
> index 80b6372cf7..9dfbce702e 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -1154,6 +1154,7 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path,
>  const char *real_path(const char *path);
>  const char *real_path_if_valid(const char *path);
>  char *real_pathdup(const char *path);
> +char *real_pathdup_gently(const char *path);
>  const char *absolute_path(const char *path);
>  char *absolute_pathdup(const char *path);
>  const char *remove_leading_path(const char *in, const char *prefix);
> diff --git a/setup.c b/setup.c
> index f14cbcd338..398ea8a913 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -806,7 +806,7 @@ static int canonicalize_ceiling_entry(struct string_list_item *item,
>  		/* Keep entry but do not canonicalize it */
>  		return 1;
>  	} else {
> -		char *real_path = real_pathdup(ceil);
> +		char *real_path = real_pathdup_gently(ceil);
>  		if (!real_path) {
>  			return 0;
>  		}
> diff --git a/t/t1501-work-tree.sh b/t/t1501-work-tree.sh
> index 046d9b7909..b06210ec5e 100755
> --- a/t/t1501-work-tree.sh
> +++ b/t/t1501-work-tree.sh
> @@ -423,7 +423,7 @@ test_expect_success '$GIT_WORK_TREE overrides $GIT_DIR/common' '
>  	)
>  '
>  
> -test_expect_failure 'error out gracefully on invalid $GIT_WORK_TREE' '
> +test_expect_success 'error out gracefully on invalid $GIT_WORK_TREE' '
>  	(
>  		GIT_WORK_TREE=/.invalid/work/tree &&
>  		export GIT_WORK_TREE &&
> -- 
> 2.12.0
> 

-- 
Brandon Williams