Subject: Re: [PATCH] strbuf: add strbuf_add_real_path()

From: Brandon Williams <[email-masked]>
Date: Mon, 27 Feb 2017 10:22:17 -0800

On 02/25, René Scharfe wrote:
> Add a function for appending the canonized absolute pathname of a given
> path to a strbuf.  It keeps the existing contents intact, as expected of
> a function of the strbuf_add() family, while avoiding copying the result
> if the given strbuf is empty.  It's more consistent with the rest of the
> strbuf API than strbuf_realpath(), which it's wrapping.
> 
> Also add a semantic patch demonstrating its intended usage and apply it
> to the current tree.  Using strbuf_add_real_path() instead of calling
> strbuf_addstr() and real_path() avoids an extra copy to a static buffer.
> 

Seems like a reasonable thing to do.  When I wrote strbuf_realpath() I
think I looked at the strbuf_getcwd() function for what it did (since it
handled paths) and it simply uses the provided buffer disregarding what
is already stored in it.

> Signed-off-by: Rene Scharfe <[email-masked]>
> ---
>  contrib/coccinelle/strbuf.cocci |  6 ++++++
>  setup.c                         |  2 +-
>  strbuf.c                        | 11 +++++++++++
>  strbuf.h                        | 14 ++++++++++++++
>  4 files changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/contrib/coccinelle/strbuf.cocci b/contrib/coccinelle/strbuf.cocci
> index 63995f22ff..1d580e49b0 100644
> --- a/contrib/coccinelle/strbuf.cocci
> +++ b/contrib/coccinelle/strbuf.cocci
> @@ -38,3 +38,9 @@ expression E1, E2, E3;
>  @@
>  - strbuf_addstr(E1, find_unique_abbrev(E2, E3));
>  + strbuf_add_unique_abbrev(E1, E2, E3);
> +
> +@@
> +expression E1, E2;
> +@@
> +- strbuf_addstr(E1, real_path(E2));
> ++ strbuf_add_real_path(E1, E2);
> diff --git a/setup.c b/setup.c
> index 967f289f1e..f14cbcd338 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -254,7 +254,7 @@ int get_common_dir_noenv(struct strbuf *sb, const char *gitdir)
>  		if (!is_absolute_path(data.buf))
>  			strbuf_addf(&path, "%s/", gitdir);
>  		strbuf_addbuf(&path, &data);
> -		strbuf_addstr(sb, real_path(path.buf));
> +		strbuf_add_real_path(sb, path.buf);
>  		ret = 1;
>  	} else {
>  		strbuf_addstr(sb, gitdir);
> diff --git a/strbuf.c b/strbuf.cq
> index 8fec6579f7..ace58e7367 100644
> --- a/strbuf.c
> +++ b/strbuf.c
> @@ -707,6 +707,17 @@ void strbuf_add_absolute_path(struct strbuf *sb, const char *path)
>  	strbuf_addstr(sb, path);
>  }
>  
> +void strbuf_add_real_path(struct strbuf *sb, const char *path)
> +{
> +	if (sb->len) {
> +		struct strbuf resolved = STRBUF_INIT;
> +		strbuf_realpath(&resolved, path, 1);
> +		strbuf_addbuf(sb, &resolved);
> +		strbuf_release(&resolved);
> +	} else
> +		strbuf_realpath(sb, path, 1);

I know its not required but I would have braces on the 'else' branch
since they were needed on the 'if' branch.  But that's up to you and
your style :)

> +}
> +
>  int printf_ln(const char *fmt, ...)
>  {
>  	int ret;
> diff --git a/strbuf.h b/strbuf.h
> index cf1b5409e7..cf8e4bf532 100644
> --- a/strbuf.h
> +++ b/strbuf.h
> @@ -441,6 +441,20 @@ extern int strbuf_getcwd(struct strbuf *sb);
>   */
>  extern void strbuf_add_absolute_path(struct strbuf *sb, const char *path);
>  
> +/**
> + * Canonize `path` (make it absolute, resolve symlinks, remove extra
> + * slashes) and append it to `sb`.  Die with an informative error
> + * message if there is a problem.
> + *
> + * The directory part of `path` (i.e., everything up to the last
> + * dir_sep) must denote a valid, existing directory, but the last
> + * component need not exist.
> + *
> + * Callers that don't mind links should use the more lightweight
> + * strbuf_add_absolute_path() instead.
> + */
> +extern void strbuf_add_real_path(struct strbuf *sb, const char *path);
> +
>  
>  /**
>   * Normalize in-place the path contained in the strbuf. See
> -- 
> 2.12.0
> 

-- 
Brandon Williams