unit_move() is too big and has too many paths through its loop.
Maintenance of the (unspoken) loop invariant isn't obvious. In fact,
it isn't maintained on some paths. I found several bugs:
* We check prerequisite conditions for moving before the first move
and around prompts. When a condition becomes wrong on the move,
movement continues all the same until the next prompt. I believe
the only way this can happen is loss of crew due to hitting a mine.
* We cache ships and land units in a list of struct ulist. When a
ship or land unit gets left behind, its node is removed from the
list and freed.
We keep pointer flg pointing to the flagship in that list for
convenience. However, the pointer isn't updated until the next
prompt. It's referenced for automatic radar and all sub-commands
other than the six directions and 'h'. Use after free when such a
sub-command gets processed after a flagship change without a prompt.
Same for land units. For instance, navigating a pair of ships "jh"
where the flagship has no mobility leaves the flagship behind, then
attempts to radar automatically using the ship in the freed list
node. Likewise, marching a similar pair of land units "jl" examines
the land unit in the freed list node to figure out how to look.
* We cache mobility in the same list to support fractional mobility
during movement. Movement deducts from cached mobility and writes
the result back to the ship or land unit.
If something else charges it mobility while it's in this list, the
cache becomes stale. shp_nav() and lnd_nav() reload stale caches,
but don't run often enough. For instance, when a ship hits mines,
the mine damage makes the cache stale. If a direction or 'h'
follows directly, the stale mobility is written back, clobbering the
mine hit's mobility loss.
This mess dates back to Empire 2, where it replaced a different mess.
There may be more bugs.
unit_move()'s complex control flow makes reasoning about its loop
invariant too error-prone. Rewrite the mess instead, splitting off
sensible subroutines.
Also fixes a couple of minor annoyances:
* White-space can confuse the parser. For instance, "jg l" is
interpreted like "jgll". Fix to reject the space. Broken in commit
0c12d83, v4.3.7.
* The flagship uses radar automatically before any sub-command (since
Chainsaw), and all ships use it automatically after a move (since
4.2.2). Make them all use it before and after each sub-command,
whether it's a move or not.
* Land units don't use radar automatically. Make them use it just
like ships.
* Always report a flagship / leader change right when it happens, not
only before and after a prompt.
Left for another day, marked FIXME: BTU charging is unclean.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Commit cd8d742 mechanically combined struct mlist's mcp and struct
llist's llp into struct ulist's chrp, adding type casts to every use.
Not necessary, simply use mchr[] and lchr[] directly.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Commit d94d269 combined them into unit_put(), but that has turned out
not to be useful. Split them again.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Members x, y, eff, supplied are not "LAND only", they're used only by
ground combat. They're not used by march.
In ground combat, member mobil is not how much the land unit has left,
it's how much it still needs to be charged.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Edit lets deities load units onto remote carriers, resulting in a
carriers having cargo in another sector. Not good. Cargo gets
teleported to its carrier belatedly when the carrier moves.
Better let edit take care of the teleport.
Also tell the deity that he just caused a teleport. Necessary to give
the deity a chance to catch unexpected changes, e.g. a player moving a
plane right before the deity edits it. Watching out for such changes
is especially important with non-interactive edit.
Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
When units somehow get stuck on a dead carrier, a new build reusing
the dead carrier's UID picks up its cargo. The cargo gets teleported
to its new carrier when the carrier moves.
Oops when a ship, plane or land unit is created with cargo. To
recover, destroy the cargo.
ef_open() handles onresize() failing incorrectly. Instead of fixing
that, drop the failure mode. It's not really used: unit_onresize()
fails only when used incorrectly. It isn't. If it ever is, ignoring
the failure is safe.
Why upgrade? I'm not a lawyer, but here's my take on the differences
to version 2:
* Software patents: better protection against abuse of patents to
prevent users from exercising the rights under the GPL. I doubt
we'll get hit with a patent suit, but it's a good move just on
general principles.
* License compatibility: compatible with more free licenses, i.e. can
"steal" more free software for use in Empire. I don't expect to steal
much, but it's nice to have the option.
* Definition of "source code": modernization of some details for today's
networked world, to make it easier to distribute the software. Not
really relevant to us now, as we normally distribute full source code.
* Tivoization: this is about putting GPL-licensed software in hardware,
then make the hardware refuse to run modified software. "Neat" trick
to effectively deny its users their rights under the GPL. Abuse was
"pioneered" by TiVo (popular digital video recorders). GPLv3 forbids
it. Unlikely to become a problem for us.
* Internationalization: more careful wording, to harden the license
outside the US. The lawyers tell us it better be done that way.
* License violations: friendlier way to deal with license violations.
This has come out of past experience enforcing the GPL.
* Additional permissions: Probably not relevant to us.
Also include myself in the list of principal authors.
Use new unit_wipe_orders() for violent takeover (takeover_unit() on
behalf of assault, attack, board, lboard, paradrop and pboard), and
peaceful takeover (unit_give_away() on behalf of arm, disarm, load,
unload, lload, lunload, scrap, scuttle, tend, trade).
Before, takeover_unit() cleared only group, mission and ship retreat
orders, and unit_give_away() only group and mission. Orders that
weren't cleared:
* Mission op area (visible in xdump)
* Ship autonav orders
* Ship sail path including ship to follow and mobility quota
* Plane range limit
* Land unit retreat orders and retreat percentage
When giving away cargo by scrapping or scuttling its carrier, the
cargo's cargo wasn't given away. Happened for instance when a ship
carrying a land unit carrying a SAM got scrapped.
Also, wing, army and mission weren't cleared.
To fix, create unit_give_away() and use it in unit_drop_cargo().
Factor unit_drop_cargo() out of scra(), scuttle_ship(),
scuttle_land(), fix it up:
* Some messages were sent as bulletins instead of printing them.
* Nukes were always destroyed. They're now treated exactly like other
cargo.
* scuttle destroyed some cargo silently, and listed other cargo as
"scuttled". It now simply lets unit_update_cargo() running from
carrier prewrite callbacks list all cargo "lost".
Simplify its callers. scuttle_ship() and scuttle_land() are now
trivial, inline and remove.
The old code did not move a carrier's cargo (planes, land units,
nukes) when the carrier moved. Instead, it fixed up the location in
the postread callback. Anything not going through ef_read(), in
particular the update, saw it in its old, incorrect location, until a
fixed up copy got written back.
Moreover, the timestamp did not change when cargo moved, so
incremental dumps did not pick up the movement.
The new code moves the cargo along with the carrier.
New unit_update_cargo() moves or destroys a carrier's cargo (planes,
land units, nukes) along with the carrier. Call it from
shp_prewrite(), pln_prewrite() and lnd_prewrite() when the carrier
moves or gets destroyed.
Remove the code to destroy cargo from shp_prewrite(), pln_prewrite(),
lnd_prewrite().
Remove the code to fix up cargo location from pln_postread(),
lnd_postread(), nuk_postread().
This changes the message for ship and land unit cargo getting
destroyed from "sunk" and "MIA" to "lost".
Load counters are redundant; they can be computed from the carrier
uids. Keeping them up-to-date as the carriers change is a pain, and
we never got that quite complete.
Computing load counters straight from the carrier uids every time we
need them would be rather inefficient, but computing them from cargo
lists is not. So do that.
Remove the load counters: struct shpstr members shp_nplane,
shp_nchoppers, shp_nxlight, shp_nland, and struct lndstr members
lnd_nxlight and lnd_nland.
Don't compute/update load counters in build_ship(), build_land(),
land(), ldump(), load_plane_ship(), load_land_ship(),
load_plane_land(), load_land_land(), lstat(), sdump(), shi(), sstat(),
tend_land(), check_trade(), put_combat(), pln_oneway_to_carrier_ok),
pln_newlanding(), fit_plane_on_ship(), fit_plane_on_land(),
unit_list().
Nothing left in fit_plane_off_ship(), fit_plane_off_land(), so remove
them.
load_land_ship(), load_land_land(), check_trade(), pln_newlanding(),
put_plane_on_ship(), take_plane_off_ship(), put_plane_on_land(),
take_plane_off_land() no longer change the carrier, so don't put it.
Remove functions to recompute the load counters from carrier uids:
count_units(), lnd_count_units(), count_planes(), count_land_planes(),
pln_fixup() and lnd_fixup(), along with the latter two's private
copies of fit_plane_on_ship() and fit_plane_on_land().
New cargo list functions to compute load counts: unit_cargo_count()
and unit_nplane(), with convenience wrappers shp_nplane(),
shp_nland(), lnd_nxlight(), lnd_nland().
Use them to make ship selectors nplane, nchoppers, nxlight, nland
virtual. They now reflect what is loaded, not how the load uses the
available slots. This makes a difference when x-light planes or
choppers use plane slots.
Use them to make land unit selectors nxlight and nland virtual.
Use them to get load counts in land(), ldump(), load_plane_ship(),
load_land_ship(), load_plane_land(), load_land_land(), sdump(), shi(),
tend_land(), fit_plane_on_land(), trade_desc(), unit_list().
Rewrite fit_plane_on_ship() and could_be_on_ship() to use
shp_nplane(). could_be_on_ship() now takes load count arguments, as
computed by shp_nplane(), so it can be used for checking against an
existing load as well.
Persistent game state encodes "who carries what" by storing the
carrier uid in the cargo. Cargo lists augment that: they store lists
of cargo for each carrier. They are not persistent.
New unit_cargo_init() to compute the cargo lists from game state.
Call it in ef_init_srv() and at the end of update_main().
New unit_onresize() to resize the cargo list data structure.
Installed as units' struct empfile callback onresize to make them
resize automatically with the unit files.
New unit_carrier_change() to update cargo lists when carriers change
in game state. Convenience wrappers pln_carrier_change(),
lnd_carrier_change() and nuk_carrier_change(). Call them from
prewrite callbacks to keep cargo lists in sync with game state.
To make that work, unused units must not point to a carrier. Add new
pln_oninit(), lnd_oninit() and nuk_oninit() take care of newly created
units. Change lnd_prewrite() and nuk_prewrite() to take dead land
units and nukes off their carrier. pln_prewrite() did that already.
New unit_cargo_first(), unit_cargo_next() to traverse cargo lists.
Convenience wrappers lnd_first_on_ship(), lnd_first_on_land(),
lnd_next_on_unit(), pln_first_on_ship(), pln_first_on_land(),
pln_next_on_unit() and nuk_on_plane(). The latter is disabled for now
because it clashes with an existing function.
land_unit as well.
(do_unit_move): Add view option for land units using unit_view().
Combine ship and land viewing using the unit_view().
(shp_view): Remove, not used any more, replaced by unit_view().
