Re: [PATCH] tree-walk.c: fix some sparse 'NULL pointer' warnings

> Commit 811cd77b ("tree-walk: learn get_tree_entry_follow_symlinks",
> 14-05-2015) introduced a new function to locate an object by path
> while following symlinks in the repository. However, sparse now
> issues some "Using plain integer as NULL pointer" warnings as
> follows:
> 
>       SP tree-walk.c
>   tree-walk.c:517:31: warning: Using plain integer as NULL pointer
>   tree-walk.c:521:28: warning: Using plain integer as NULL pointer
> 
> The first warning relates to the use of an '{0}' initializer for
> the 'struct tree_desc' t. The first field of this structure has
> pointer type. A simple solution would replace the initializer
> expression with '{NULL}'. However, we choose to remove the
> initializer expression and make the initialization more explicit
> with a call to the 'init_tree_desc' function.
> 
> The second warning relates to the '0' initializer for the buf
> field of the 'result_path' strbuf pointer. A simple solution
> would replace this initializer with 'NULL'. However, this would
> violate a strbuf invariant that the 'buf' field is never NULL.
> (see strbuf documentation in strbuf.h header.) Assuming the
> documentation of 'get_tree_entry_follow_symlinks' regarding the
> 'result_path' parameter is observed by callers (ie that the
> parameter points to an _unitialized_ strbuf), a better solution
> is to simply call the 'strbuf_init' function.
> 
> Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
> ---
> 
> Hi David,
> 
> If you need to re-roll the patches in your 'dt/cat-file-follow-symlinks'
> branch, could you please squash this, or something like this, into the
> relevant patch (commit 811cd77b).
> 
> Thanks!
> 
> ATB,
> Ramsay Jones
> 
>  tree-walk.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/tree-walk.c b/tree-walk.c
> index 8031f3a..6dccd2d 100644
> --- a/tree-walk.c
> +++ b/tree-walk.c
> @@ -514,13 +514,12 @@ enum follow_symlinks_result get_tree_entry_follow_symlinks(unsigned char *tree_s
>  	ssize_t parents_nr = 0;
>  	unsigned char current_tree_sha1[20];
>  	struct strbuf namebuf = STRBUF_INIT;
> -	struct tree_desc t = {0};
> +	struct tree_desc t;
>  	int follows_remaining = GET_TREE_ENTRY_FOLLOW_SYMLINKS_MAX_LINKS;
>  	int i;
>  
> -	result_path->buf = 0;
> -	result_path->alloc = 0;
> -	result_path->len = 0;
> +	init_tree_desc(&t, NULL, 0UL);
> +	strbuf_init(result_path, 0);
>  	strbuf_addstr(&namebuf, name);
>  	hashcpy(current_tree_sha1, tree_sha1);
>