These ships could only use their x-light slots for x-light planes, not
their plane slots. For instance, agc (30 x-light slots, 32 plane
slots) could load only 30 sams, and mb (0 x-light slots, 10 plane
slots) could not load any sams.
Culprit is could_be_on_ship(). Broken in commit 3e370da5, v4.3.17.
When an inefficient missile exploded on launch, it could damage
itself. The damage had no effect, because the missile gets used up
right after. But it triggers a seqno mismatch oops, in laun(). Fix
by making msl_launch() set PLN_LAUNCHED before the explosion.
This case was missed in commit 7bc63871, v4.3.14. It didn't oops
until sequence numbers were added in v4.3.15.
When d of n cargo items are discarded for want of space, pln_dropoff()
reported -d items discarded and -d items unloaded. Already broken in
BSD Empire 1.1.
Before commit a269cdd7, pln_damage() returned zero when the damage was
nuclear, and callers used that to bypass conventional damage code.
Zero value can't happen anymore.
Ships can expend shells to defend against missiles, in
shp_missile_defense(). Any shell use by the target ship got wiped out
when shp_missile_interdiction() wrote back the target ship, triggering
a seqno mismatch oops.
Ships get updated when they launch planes to intercept interdicting
planes, in mission_pln_equip(). Any petrol use by the target ship got
wiped out when shp_mission_interdiction() wrote back the target ship,
triggering a seqno mismatch oops.
Fix by re-reading the target ship in shp_damage_one(). This also
affects shp_fort_interdiction(), where it is not necessary. A bit
inefficient, but let's keep this fix simple.
Commit a269cdd7 (v4.3.23) removed the nuclear damage. But it left the
nuke on the missile, which made pln_damage() oops and return zero
damage.
Fix by destroying the nuke separately.
Movement stops when shp_interdict() or lnd_interdict() report
interdiction. However, they reported it only when there was
interdiction damage.
Zero interdiction damage commonly happens when interdicting missiles
miss, or all bombers abort. Stopping regardless of damage makes more
sense there.
Moreover, not stopping is buggy: do_unit_move() needs to take care not
to wipe out updates made by interdiction to the moving ships or land
units. It does so only when it stops. Updates made by interdiction
without interdiction damage could get wiped out, triggering a seqno
mismatch oops.
Known ways moving ships and land units can get updated by interdiction
despite there is no interdiction damage:
* Interdicting bombers get intercepted by planes based on a navigating
carrier, carrier gets charged petrol. The bug wipes out the petrol
use.
* Marching land units get interdicted by planes, but all planes miss.
Sufficiently large collateral damage to the sector can still damage
the land units. The bug wipes out the damage to land units.
To make shp_interdict() and lnd_interdict() report interdiction
regardless of damage, change lnd_missile_interdiction(),
lnd_fort_interdiction(), lnd_mission_interdiction(),
shp_missile_interdiction(), shp_fort_interdiction(),
shp_mission_interdiction() to return whether there was interdiction.
Before, they returned whether there was damage.
Change unit_interdict(), perform_mission(), perform_mission_land(),
perform_mission_ship(), perform_mission_msl(), and
perform_mission_bomb() to return -1 for no interdiction, so that
callers can distinguish no interdiction from interdiction with no
damage.
getland() is obviously redundant in get_dlist(), because the land unit
can't have changed since the previous read.
What's up with ask_olist() is less obvious. For each capable land
unit, ask_olist() asks the player whether to attack with it. If it
attacks, it gets copied into olist. Since asking the player yields
the processor, these copies can become stale. However, re-reading
fixes that just for the last one. Moreover, the code copes with stale
copies just fine: ask_olist() is always directly followed by
att_get_offense() or att_move_in_off(), and both replace the
potentially stale copy in olist.
ask_olist() and get_dlist() called get_land() with llp->chrp still
null, which made it initialize parts of llp instead of performing its
usual integrity check. att_reacting_units() had the initialization
inline. Change the other two to match, and simplify get_land(). No
functional change.
shp_missile_interdiction() does nothing when there are no suitable
targets. Its users avoid to call it when there are none, probably to
save a few cycles. Optimize shp_missile_interdiction() for that case,
and simplify the callers.
Oops when a stale copy is written back, i.e. the processor was yielded
since the copy was made. Such bugs are difficult to spot. Sequence
numbers catch them when they do actual harm (they also catch different
bugs). Generation numbers catch them even when they don't.
New ef_generation to count generations. Call new ef_make_stale() to
increment it whenever the processor may be yielded.
New struct emptypedstr member generation. To conserve space, make it
a bit-field of twelve bits, i.e. generations are only recorded modulo
2^12. Make sure all members of unit empobj_storage share it. It is
only used in copies; its value on disk and in the cache is
meaningless. Copies with generation other than ef_generation are
stale. Stale copies that are a multiple of 2^12 generations old can't
be detected, but that is sufficiently improbable.
Set generation to ef_generation by calling new ef_mark_fresh() when
making copies in ef_read() and ef_blank(). nav_ship() and
fltp_to_list() make copies without going through ef_read(), and
therefore need to call ef_mark_fresh() as well. Also call it in
obj_changed() to make check_sect_ok() & friends freshen their argument
when it is unchanged.
New must_be_fresh() oopses when its argument is stale. Call it in
ef_write() to catch write back of stale copies.
Store them and ef_type in bit-fields.
Allocate eight bits for ef_type. Values range from 0 to EF_GAME
(currently 16), so this is plenty.
Allocate twelve bits for sequence numbers. Sequence number mismatches
are now missed when the numbers are equal modulo 2^12. Still
sufficiently improbable.
Common machines store the bit-fields in a 32 bit word. There are
twelve bits left in that word for future use. Total savings 16 bits,
which is exactly what the previous commit spent on wider uids on
common machines.
Member nws_uid is unused since the commit before previous. Remove it.
Member nws_seqno is of marginal value, because we write news only
through ncache[], and thus aren't prone to the errors sequence numbers
can catch. Remove it.
Make timestamp selector virtual, computing nws_when + nws_duration,
and remove member nws_timestamp. Impact:
* In ncache(), the removed timestamp equals nws_when + nws_duration,
both for new news and updated news. No change.
* delete_old_news() becomes invisible. Before, its move of unexpired
news to the beginning of the news file touched all the timestamps.
That was unwanted, because the move does not change news, only their
storage. Improvement.
* empdump no longer flags the imported news changed via the timestamp.
This is somewhat unfortunate. Document as bug.
With these members removed, struct nwsstr no longer matches struct
emptypedstr, so clear news table flag EFF_TYPED and remove union
empobj_storage member news. This loses the automatic maintenance of
member ef_type via struct emptypedstr. Remove ef_type as well.
This shrinks struct nwsstr from 20 to 12 bytes on common 32 bit
machines, and from 32 to 16 bytes on common 64 bit machines. Since
the server doesn't map the whole news file (EFF_MAP is off), this
reduces I/O, while the table's memory use remains the same.
Historical note: struct nwsstr is now pretty much what it was back in
BSD Empire 1.1. Members ef_type and nws_uid go back to Empire 3 (for
C_SYNC?). v4.3.12 added member nws_timestamp, which doubled the size
on common 64 bit machines. v4.3.15 added nws_seqno.
Missiles attacking ground targets (sectors, ships or land units) can
be intercepted, missiles targeting planes can't. Except msl_launch()
checked the missile's capabilities instead of its target, and thus
intercepted missiles that *could* target ground even when they
targeted planes.
This broke the missile interception code's assumption that
interceptors aren't intercepted, and crashed the server through
infinite recursion: tactical abm #1 intercepts, tactical abm #2
intercepts #1, #1 intercepts #2, ...
Same bug in msl_hit() printed "incoming missile" for missiles that
could target ground but do target planes.
Broken in Empire 2. Bug can't bite with the stock game's planes.
Collateral damage was disabled, because after msl_hit() reported a
miss, the missile may or may not have reached the target.
Fix by splitting msl_launch() off msl_hit().
Drop the disabled collateral damage code for sector targets, because
sectors can't be missed. Enable it for ships and land units.
Since msl_launch() returns whether the missile is sub-launched, drop
launch_missile() parameter sublaunch, and simplify its caller.
Keep only the common part in msl_intercept(), and give it internal
linkage. Wrap new msl_abm_intercept() and msl_asat_intercept() around
it. They are simpler to use.
