Re: [PATCH v4 8/9] Use uintmax_t for timestamps

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <johannes.schindelin@gmx.de> writes:

> Previously, we used `unsigned long` for timestamps. This was only a good
> choice on Linux, where we know implicitly that `unsigned long` is what is
> used for `time_t`.
>
> However, we want to use a different data type for timestamps for two
> reasons:
>
> - there is nothing that says that `unsigned long` should be the same data
>   type as `time_t`, and indeed, on 64-bit Windows for example, it is not:
>   `unsigned long` is 32-bit but `time_t` is 64-bit.
>
> - even on 32-bit Linux, where `unsigned long` (and thereby `time_t`) is
>   32-bit, we *want* to be able to encode timestamps in Git that are
>   currently absurdly far in the future, *even if* the system library is
>   not able to format those timestamps into date strings.
>
> So let's just switch to the maximal integer type available, which should
> be at least 64-bit for all practical purposes these days. It certainly
> cannot be worse than `unsigned long`, so...

Should we at least clamp in date_overflows() so that large values
representable with timestamp_t that will become unrepresentable when
we start allowing negative timestamps would be rejected?  That way
we won't have to hear complaints from the people who used timestamps
far in the future that we regressed the implementation for them by
halving the possible timestamp range.



> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  git-compat-util.h | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/git-compat-util.h b/git-compat-util.h
> index 72c12173a14..c678ca94b8f 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -319,10 +319,14 @@ extern char *gitdirname(char *);
>  #define PRIo32 "o"
>  #endif
>  
> -typedef unsigned long timestamp_t;
> -#define PRItime "lu"
> -#define parse_timestamp strtoul
> +typedef uintmax_t timestamp_t;
> +#define PRItime PRIuMAX
> +#define parse_timestamp strtoumax
> +#ifdef ULLONG_MAX
> +#define TIME_MAX ULLONG_MAX
> +#else
>  #define TIME_MAX ULONG_MAX
> +#endif
>  
>  #ifndef PATH_SEP
>  #define PATH_SEP ':'