[PATCH 4/6] Prepare for timestamps to use 64-bit signed types

[Johannes Schindelin <johannes.schindelin@gmx.de>]

Currently, Git's source code uses the unsigned long type to represent
timestamps. However, this type is limited to 32-bit e.g. on 64-bit
Windows. Hence it is a suboptimal type for this use case.

In any case, we need to use the time_t type to represent timestamps
since we often send those values to system functions which are declared
to accept time_t parameters.

So let's prepare for the case where timestamps are represented as 64-bit
signed integers by introducing the Makefile option TIME_T_IS_INT64.

As we have to resort to using `strtoull()` (and casting the parsed,
unsigned value to an `int64_t`), the check in the `date_overflows()`
helper has to be relaxed: a value of ULLONG_MAX (cast to `int64_t`)
now *also* indicates an overflow.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 Makefile                   | 4 ++++
 archive-tar.c              | 5 ++++-
 builtin/name-rev.c         | 2 +-
 builtin/prune.c            | 2 +-
 builtin/worktree.c         | 2 +-
 credential-cache--daemon.c | 2 +-
 date.c                     | 8 ++++----
 git-compat-util.h          | 7 +++++++
 ref-filter.c               | 2 +-
 9 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/Makefile b/Makefile
index 8e4081e0619..0232cf62d33 100644
--- a/Makefile
+++ b/Makefile
@@ -1518,6 +1518,10 @@ ifdef HAVE_GETDELIM
 	BASIC_CFLAGS += -DHAVE_GETDELIM
 endif
 
+ifdef TIME_T_IS_INT64
+	BASIC_CFLAGS += -DTIME_T_IS_INT64
+endif
+
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK = NoThanks
 endif
diff --git a/archive-tar.c b/archive-tar.c
index 380e3aedd23..695339a2369 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -27,9 +27,12 @@ static int write_tar_filter_archive(const struct archiver *ar,
  */
 #if ULONG_MAX == 0xFFFFFFFF
 #define USTAR_MAX_SIZE ULONG_MAX
-#define USTAR_MAX_MTIME ULONG_MAX
 #else
 #define USTAR_MAX_SIZE 077777777777UL
+#endif
+#if TIME_MAX == 0xFFFFFFFF
+#define USTAR_MAX_MTIME TIME_MAX
+#else
 #define USTAR_MAX_MTIME 077777777777UL
 #endif
 
diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index cd89d48b65e..a0f16407b93 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -145,7 +145,7 @@ static int name_ref(const char *path, const struct object_id *oid, int flags, vo
 	struct name_ref_data *data = cb_data;
 	int can_abbreviate_output = data->tags_only && data->name_only;
 	int deref = 0;
-	unsigned long taggerdate = ULONG_MAX;
+	unsigned long taggerdate = TIME_MAX;
 
 	if (data->tags_only && !starts_with(path, "refs/tags/"))
 		return 0;
diff --git a/builtin/prune.c b/builtin/prune.c
index 8f4f0522856..1e5eb0292b1 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -111,7 +111,7 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 	};
 	char *s;
 
-	expire = ULONG_MAX;
+	expire = TIME_MAX;
 	save_commit_buffer = 0;
 	check_replace_refs = 0;
 	ref_paranoia = 1;
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 831fe058a53..3df95e112e5 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -131,7 +131,7 @@ static int prune(int ac, const char **av, const char *prefix)
 		OPT_END()
 	};
 
-	expire = ULONG_MAX;
+	expire = TIME_MAX;
 	ac = parse_options(ac, av, prefix, options, worktree_usage, 0);
 	if (ac)
 		usage_with_options(worktree_usage, options);
diff --git a/credential-cache--daemon.c b/credential-cache--daemon.c
index 46c5937526a..b298ac01e4f 100644
--- a/credential-cache--daemon.c
+++ b/credential-cache--daemon.c
@@ -52,7 +52,7 @@ static int check_expirations(void)
 	static unsigned long wait_for_entry_until;
 	int i = 0;
 	unsigned long now = time(NULL);
-	unsigned long next = (unsigned long)-1;
+	unsigned long next = TIME_MAX;
 
 	/*
 	 * Initially give the client 30 seconds to actually contact us
diff --git a/date.c b/date.c
index 97ab5fcc349..23dee2964c1 100644
--- a/date.c
+++ b/date.c
@@ -659,7 +659,7 @@ static int match_object_header_date(const char *date, unsigned long *timestamp,
 	if (*date < '0' || '9' < *date)
 		return -1;
 	stamp = parse_timestamp(date, &end, 10);
-	if (*end != ' ' || stamp == ULONG_MAX || (end[1] != '+' && end[1] != '-'))
+	if (*end != ' ' || stamp == TIME_MAX || (end[1] != '+' && end[1] != '-'))
 		return -1;
 	date = end + 2;
 	ofs = strtol(date, &end, 10);
@@ -762,7 +762,7 @@ int parse_expiry_date(const char *date, unsigned long *timestamp)
 		 * of the past, and there is nothing from the future
 		 * to be kept.
 		 */
-		*timestamp = ULONG_MAX;
+		*timestamp = TIME_MAX;
 	else
 		*timestamp = approxidate_careful(date, &errors);
 
@@ -1184,8 +1184,8 @@ int date_overflows(unsigned long t)
 {
 	time_t sys;
 
-	/* If we overflowed our unsigned long, that's bad... */
-	if (t == ULONG_MAX)
+	/* If we overflowed our timestamp data type, that's bad... */
+	if ((uintmax_t)t >= TIME_MAX)
 		return 1;
 
 	/*
diff --git a/git-compat-util.h b/git-compat-util.h
index 4365012c536..5cf1133532d 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -319,8 +319,15 @@ extern char *gitdirname(char *);
 #define PRIo32 "o"
 #endif
 
+#ifdef TIME_T_IS_INT64
+#define PRItime PRId64
+#define parse_timestamp strtoull
+#define TIME_MAX INT64_MAX
+#else
 #define PRItime "lu"
 #define parse_timestamp strtoul
+#define TIME_MAX ULONG_MAX
+#endif
 
 #ifndef PATH_SEP
 #define PATH_SEP ':'
diff --git a/ref-filter.c b/ref-filter.c
index 6fab0db5e0d..07c1f372351 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -638,7 +638,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	if (!eoemail)
 		goto bad;
 	timestamp = parse_timestamp(eoemail + 2, &zone, 10);
-	if (timestamp == ULONG_MAX)
+	if (timestamp == TIME_MAX)
 		goto bad;
 	tz = strtol(zone, NULL, 10);
 	if ((tz == LONG_MIN || tz == LONG_MAX) && errno == ERANGE)
-- 
2.11.1.windows.1.379.g44ae0bc