Re: [PATCH] exec_cmd: system_path memory leak fix

[Eric Sunshine <sunshine@sunshineco.com>]

On Sun, Nov 23, 2014 at 2:19 PM, Alex Kuleshov <kuleshovmail@gmail.com> wrote:
>
> Signed-off-by: Alex Kuleshov <kuleshovmail@gmail.com>
> ---
>  exec_cmd.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/exec_cmd.c b/exec_cmd.c
> index 698e752..7ed9bcc 100644
> --- a/exec_cmd.c
> +++ b/exec_cmd.c
> @@ -13,7 +13,7 @@ const char *system_path(const char *path)
>  #else
>         static const char *prefix = PREFIX;
>  #endif
> -       struct strbuf d = STRBUF_INIT;
> +       static struct strbuf d = STRBUF_INIT;

Curious. Did the unit tests pass with this change?

In the original code, the strbuf starts out empty each time
system_path() is called, and strbuf_addf() populates it. After your
change, the strbuf starts empty only on the very first call, and
subsequent calls append more content rather than replacing it. At the
very least, to fix, you now need to invoke strbuf_reset() before
invoking strbuf_addf().

>         if (is_absolute_path(path))
>                 return path;
> @@ -34,8 +34,7 @@ const char *system_path(const char *path)
>  #endif
>
>         strbuf_addf(&d, "%s/%s", prefix, path);
> -       path = strbuf_detach(&d, NULL);
> -       return path;
> +       return d.buf;
>  }
>
>  const char *git_extract_argv0_path(const char *argv0)
> @@ -94,7 +93,7 @@ static void add_path(struct strbuf *out, const char *path)
>  void setup_path(void)
>  {
>         const char *old_path = getenv("PATH");
> -       struct strbuf new_path = STRBUF_INIT;
> +       static struct strbuf new_path = STRBUF_INIT;
>
>         add_path(&new_path, git_exec_path());
>         add_path(&new_path, argv0_path);

Not sure what this change is about. The last couple lines of this function are:

    setenv("PATH", new_path.buf, 1);
    strbuf_release(&new_path);

which means that the buffer held by the strbuf is being released
anyhow, whether static or not.