Re: [PATCH 2/2] read-cache: use time_t instead of unsigned long

> There are still some more possible improvements around this code but
> they are orthogonal to this change :
> 
> * migrate to approxidate_careful or parse_expiry_date
> * maybe make sure only approxidate are used for expiration
> 
> Changes in v2:
> * improved commit message as suggested by Eric
> * failsafe against time_t truncation as suggested by Junio
> 
> -- >8 --
> Subject: [PATCH v2 2/2] read-cache: use time specific types instead of
>  unsigned long
> 
> b968372279 ("read-cache: unlink old sharedindex files", 2017-03-06)
> introduced get_shared_index_expire_date using unsigned long to track
> the modification times of a shared index.
> 
> dddbad728c ("timestamp_t: a new data type for timestamps", 2017-04-26)
> shows why that might be problematic so move to timestamp_t/time_t.
> 
> if time_t can't represent a valid time keep the indexes for failsafe

> 
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
>  read-cache.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/read-cache.c b/read-cache.c
> index 7b1354d759..7d322f11c8 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -2625,9 +2625,9 @@ static int write_split_index(struct index_state *istate,
>  
>  static const char *shared_index_expire = "2.weeks.ago";
>  
> -static unsigned long get_shared_index_expire_date(void)
> +static timestamp_t get_shared_index_expire_date(void)
>  {
> -	static unsigned long shared_index_expire_date;
> +	static timestamp_t shared_index_expire_date;
>  	static int shared_index_expire_date_prepared;
>  
>  	if (!shared_index_expire_date_prepared) {
> @@ -2643,12 +2643,12 @@ static unsigned long get_shared_index_expire_date(void)
>  static int should_delete_shared_index(const char *shared_index_path)
>  {
>  	struct stat st;
> -	unsigned long expiration;
> +	time_t expiration;
> +	timestamp_t t = get_shared_index_expire_date();
>  
> -	/* Check timestamp */
> -	expiration = get_shared_index_expire_date();
> -	if (!expiration)
> +	if (!t || date_overflows(t))
>  		return 0;
> +	expiration = t;
>  	if (stat(shared_index_path, &st))
>  		return error_errno(_("could not stat '%s'"), shared_index_path);
>  	if (st.st_mtime > expiration)
> -- 
> 2.19.1.856.g8858448bb
> 
>