On Mon, 2022-05-23 at 14:57 -0400, Derrick Stolee wrote:
> On 5/21/22 9:53 AM, Kevin Locke wrote:
> > + free((char*)tmp_original_cwd);
>
> Hm. I'm never a fan of this casting, but it existed before. It's
> because tmp_original_cwd is exposed globally in cache.h, which
> is _really widely_. However, there are only two uses: setup.c,
> which defines it, and common-main.c, which initializes it during
> process startup.
>
> The following diff could apply before your commit, removing this
> use of "const char *", but maybe it doesn't fit normal Git
> coding guidelines (putting the extern directly in a *.c file):
>
> --- >8 ---
>
> diff --git a/cache.h b/cache.h
> index aaf334e2aa4..ce9cd6fa3f0 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -1797,7 +1797,6 @@ struct startup_info {
> const char *original_cwd;
> };
> extern struct startup_info *startup_info;
> -extern const char *tmp_original_cwd;
>
> /* merge.c */
> struct commit_list;
> diff --git a/common-main.c b/common-main.c
> index 29fb7452f8a..e472258b83b 100644
> --- a/common-main.c
> +++ b/common-main.c
> @@ -23,6 +23,8 @@ static void restore_sigpipe_to_default(void)
> signal(SIGPIPE, SIG_DFL);
> }
>
> +extern char *tmp_original_cwd;
> +
> int main(int argc, const char **argv)
> {
> int result;
> diff --git a/setup.c b/setup.c
> index 04ce33cdcd4..86986317490 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -12,7 +12,7 @@ static int work_tree_config_is_bogus;
>
> static struct startup_info the_startup_info;
> struct startup_info *startup_info = &the_startup_info;
> -const char *tmp_original_cwd;
> +char *tmp_original_cwd;
>
> /*
> * The input parameter must contain an absolute path, and it must already be
> @@ -459,7 +459,7 @@ static void setup_original_cwd(void)
>
> /* Normalize the directory */
> strbuf_realpath(&tmp, tmp_original_cwd, 1);
> - free((char*)tmp_original_cwd);
> + free(tmp_original_cwd);
> tmp_original_cwd = NULL;
> startup_info->original_cwd = strbuf_detach(&tmp, NULL);
>
> --- >8 ---
This approach seems reasonable to me, as does casting to free(). It's
not clear to me which is preferable in this case. How to balance the
trade-offs between exposing const interfaces, limiting (internal)
interfaces to headers, and avoiding casts might be worth discussing
and documenting a matter of project coding style. `grep -rF 'free(('`
lists about 100 casts to free, suggesting the discussion may be
worthwhile. Introducing a free_const() macro could be another option
to consider.
>> + tmp_original_cwd = NULL;
>> + startup_info->original_cwd = strbuf_detach(&tmp, NULL);
>> + } else {
>> + trace_printf("realpath(cwd) failed: %s\n", strerror(errno));
>
> It could also be helpful to include a trace2 output, since
> most modern tracing uses that mechanism:
>
> trace2_data_string("setup", the_repository,
> "realpath-path", tmp_original_cwd);
> trace2_data_string("setup", the_repository,
> "realpath-failure", strerror(errno));
>
> But this is also unlikely to be necessary. We can instruct
> a user to rerun their command with GIT_TRACE=1 if we see
> this error in the wild.
That's a great idea. I hadn't realized the difference between the
trace_* and trace2_* APIs until investigating as a result of your
suggestion. Trace2 seems preferable for many reasons. I'll send an
updated patch shortly.
Thanks for the review and feedback Stolee!
Cheers,
Kevin
