The timezones that we store in commits as part of the identity
information are encoded in "[+-]HHMM", for example "-0700" for UTC-7.
Internally we typically pass around this timezone either as string or as
a parsed integer (-700).
Some sites want to convert between this format and minutes or vice
versa, and that conversion is performed ad-hoc. We're about to introduce
another site though that wants to have access to this logic, and having
it cluttered across our codebase is a bit awkward.
Introduce two new helpers `tz_to_minutes()` and `minutes_to_tz()` that
perform the conversion for us and convert call sites to use them.
Note that we used to perform a dance in `gm_time_t()` where we first
convert `tz` into a positive value, then calculate the minutes, and
finally turn the minutes into a negative value again. This dance is
performed because it is implementation-defined in C89 whether the
division on negative values truncates towards zero or not [1]:
If either operand is negative, whether the result of the / operator is
the largest integer less than the algebraic quotient or the smallest
integer greater than the algebraic quotient is implementation-defined,
as is the sign of the result of the % operator.
So under C89, `-130 / 100` could legitimately result in -1 or -2, and
`-130 % 100` could result in either -30 or 70. For us though, the result
that we want is the first one (-1 and -30), which is called truncation
toward zero.
This part of the C language has changed in C99, where this edge case is
now well-defined to always truncate towards zero [2]:
When integers are divided, the result of the / operator is the
algebraic quotient with any fractional part discarded.90) If the
quotient a/b is representable, the expression (a/b)*b + a%b shall
equal a.
90) This is often called ''truncation toward zero''.
So in theory it's unlikely that we still need this logic. In practice
though it feels safer to just retain it as we don't require a fully
C99-compliant compiler in Git.
[1]: https://port70.net/~nsz/c/c89/c89-draft.html#3.3.5
[2]: https://port70.net/~nsz/c/c99/n1256.html#6.5.5p6
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
date_mode_from_type() modifies a static variable and returns a pointer
to it. This is not thread-safe. Most callers of date_mode_from_type()
use it via the macro DATE_MODE and pass its result on to functions like
show_date(), which take a const pointer and don't modify the struct.
Avoid the static storage by putting the variable on the stack and
returning the whole struct date_mode. Change functions that take a
constant pointer to expect the whole struct instead.
Reduce the cost of passing struct date_mode around on 64-bit systems
by reordering its members to close the hole between the 32-bit wide
.type and the 64-bit aligned .strftime_fmt as well as the alignment
hole at the end. sizeof reports 24 before and 16 with this change
on x64. Keep .type at the top to still allow initialization without
designator -- though that's only done in a single location, in
builtin/blame.c.
Signed-off-by: René Scharfe <l.s.r@web.de>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When 29f4332e66 (Quit passing 'now' to date code, 2019-09-11) removed
its timeval parameter, approxidate_relative() became equivalent to
approxidate(). Convert its last two call sites and remove the redundant
function.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix a memory leak in the parse_date_format() function by providing a
new date_mode_release() companion function.
By using this in "t/helper/test-date.c" we can mark the
"t0006-date.sh" test as passing when git is compiled with
SANITIZE=leak, and whitelist it to run under
"GIT_TEST_PASSING_SANITIZE_LEAK=true" by adding
"TEST_PASSES_SANITIZE_LEAK=true" to the test itself.
The other tests that expose this memory leak (i.e. take the
"mode->type == DATE_STRFTIME" branch in parse_date_format()) are
"t6300-for-each-ref.sh" and "t7004-tag.sh". The former is due to an
easily fixed leak in "ref-filter.c", and brings the failures in
"t6300-for-each-ref.sh" down from 51 to 48.
Fixing the remaining leaks will have to wait until there's a
release_revisions() in "revision.c", as they have to do with leaks via
"struct rev_info".
There is also a leak in "builtin/blame.c" due to its call to
parse_date_format() to parse the "blame.date" configuration. However
as it declares a file-level "static struct date_mode blame_date_mode"
to track the data, LSAN will not report it as a leak. It's possible to
get valgrind(1) to complain about it with e.g.:
valgrind --leak-check=full --show-leak-kinds=all ./git -P -c blame.date=format:%Y blame README.md
But let's focus on things LSAN complains about, and are thus
observable with "TEST_PASSES_SANITIZE_LEAK=true". We should get to
fixing memory leaks in "builtin/blame.c", but as doing so would
require some re-arrangement of cmd_blame() let's leave it for some
other time.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add basic API doc comments to date.h, and while doing so move the the
parse_date_format() function adjacent to show_date(). This way all the
"struct date_mode" functions are grouped together. Documenting the
rest is one of our #leftoverbits.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Provide and use a DATE_MODE_INIT macro. Most of the users of struct
date_mode" use it via pretty.h's "struct pretty_print_context" which
doesn't have an initialization macro, so we're still bound to being
initialized to "{ 0 }" by default.
But we can change the couple of callers that directly declared a
variable on the stack to instead use the initializer, and thus do away
with the "mode.local = 0" added in add00ba2de (date: make "local"
orthogonal to date format, 2015-09-03).
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the declaration of the date.c functions from cache.h, and adjust
the relevant users to include the new date.h header.
The show_ident_date() function belonged in pretty.h (it's defined in
pretty.c), its two users outside of pretty.c didn't strictly need to
include pretty.h, as they get it indirectly, but let's add it to them
anyway.
Similarly, the change to "builtin/{fast-import,show-branch,tag}.c"
isn't needed as far as the compiler is concerned, but since they all
use the "DATE_MODE()" macro we now define in date.h, let's have them
include it.
We could simply include this new header in "cache.h", but as this
change shows these functions weren't common enough to warrant
including in it in the first place. By moving them out of cache.h
changes to this API will no longer cause a (mostly) full re-build of
the project when "make" is run.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Patrick Steinhardt