RE: [Outreachy][PATCH 1/2] date: refactor 64 bit prereq code into reusable functions

[<rsbecker@nexbridge.com>]

On Monday, February 5, 2024 11:25 AM, Achu Luma wrote:
>In a following commit we are going to port code from "t/helper/test-date.c"
and
>"t/t0006-date.sh" to a new "t/unit-tests/t-date.c" file using the recently
added unit
>test framework.
>
>We cannot fully port all the code from "t/helper/test-date.c" though, as
the test-
>tool date helper is still used by a number of "t/*.sh" tests.
>The TIME_IS_64BIT and TIME_T_IS_64BIT prereqs are especially used by
"t5000-
>tar-tree.sh", "t5318-commit-graph.sh" and
"t5328-commit-graph-64bit-time.sh"
>while checking those prereqs will be required in the new
"t/unit-tests/t-date.c" file
>too.
>
>To avoid duplicating in both "t/helper/test-date.c" and
"t/unit-tests/t-date.c" the
>small amount of code checking these prereqs, let's move it into inline
functions in
>"date.h".
>
>The names of these new inline functions contain "TIME_IS_64BIT" or
>"TIME_T_IS_64BIT" as it will simplify the macros we will use when we will
port code
>to "t/unit-tests/t-date.c" in a following commit.
>
>Mentored-by: Christian Couder <chriscool@tuxfamily.org>
>Signed-off-by: Achu Luma <ach.lumap@gmail.com>
>---
> date.h               | 6 ++++++
> t/helper/test-date.c | 4 ++--
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
>diff --git a/date.h b/date.h
>index 6136212a19..fb70490a51 100644
>--- a/date.h
>+++ b/date.h
>@@ -70,4 +70,10 @@ void datestamp(struct strbuf *out);  timestamp_t
>approxidate_careful(const char *, int *);  int date_overflows(timestamp_t
date);
>time_t tm_to_time_t(const struct tm *tm);
>+static inline int check_prereq_TIME_IS_64BIT(void) {
>+	return sizeof(timestamp_t) == 8;
>+}
>+static inline int check_prereq_TIME_T_IS_64BIT(void) {
>+	return sizeof(time_t) == 8;
>+}
> #endif
>diff --git a/t/helper/test-date.c b/t/helper/test-date.c index
>0683d46574..be0b8679c3 100644
>--- a/t/helper/test-date.c
>+++ b/t/helper/test-date.c
>@@ -126,9 +126,9 @@ int cmd__date(int argc UNUSED, const char **argv)
> 	else if (!strcmp(*argv, "getnanos"))
> 		getnanos(argv+1);
> 	else if (!strcmp(*argv, "is64bit"))
>-		return sizeof(timestamp_t) == 8 ? 0 : 1;
>+		return !check_prereq_TIME_IS_64BIT();
> 	else if (!strcmp(*argv, "time_t-is64bit"))
>-		return sizeof(time_t) == 8 ? 0 : 1;
>+		return !check_prereq_TIME_T_IS_64BIT();
> 	else
> 		usage(usage_msg);
> 	return 0;
>--
>2.43.0.windows.1

I would suggest that you also take into account whether time_t is signed or
not (more difficult perhaps). Some platforms use signed time_t to allow
representation of dates prior to 1970-01-01, while others make this signed.
Some other platforms (S/390 for example) have retained time_t as 32-bits but
have a time64_t for 64 bits. It might be useful to account for this.
--Randall