Added the concept of control messages to the warning system, plus the
implementation of the controls "@on"/"@off" to turn warnings on/off.
Moreover, the warning system in the test library adds some other
controls to ease the test of warnings.
When initializing a to-be-closed variable, check whether it has a
'__close' metamethod (or is a false value) and raise an error if
if it hasn't. This produces more accurate error messages. (The
check before closing still need to be done: in the C API, the value
is not constant; and the object may lose its '__close' metamethod
during the block.)
The test "to-be-closed variables in main chunk" was broken,
as it used the removed feature of functions as to-be-closed values.
The error was not detected because its expected result had no lines
to be checked (due to missing new lines).
Attributes changed to posfixed ('x <const>', instead of '<const> x'),
and "toclose" renamed to "close". Posfixed attributes seem to make it
clearer that it applies to only one variable when there are multiple
variables.
Instead of updating 'L->top' in every place that may call a
metamethod, the metamethod functions themselves (luaT_trybinTM and
luaT_callorderTM) correct the top. (When calling metamethods from
the C API, however, the callers must preserve 'L->top'.)
- OP_NEWTABLE can use 'ra + 1' to set top (instead of ci->top);
- OP_CLOSE doesn't need to set top ('Protect' already does that);
- OP_TFORCALL must use 'ProtectNT', to preserve the top already set.
(That was a small bug, because iterators could be called with
extra parameters besides the state and the control variable.)
- Comments and an extra test for the bug in previous item.
As an example, 'print(string.format("%.99f", 1e70))' may have a
lot of garbage after the number.
The old test to ensure that 'string.format("%.99f", n)' was not too
large, 'fabs(n) < 1e100', assumes that the number will fit in the 99
bytes; but the 99 is not the space for the number, it is the added
extra zeros. The option worked for smaller numbers because of the
extra space added to MAX_ITEM.
The addresses of static variables may be different for different
instances of Lua, making these instances incompatible if they use
these addresses as unique keys in the registry (or other tables).
- Macro 'checkliveness' (for debug) always uses 'L', to avoid warnings.
- Some old 'while' changed to 'for' in 'testes/gc.lua'.
- In 'testes/libs/makefile', do not make files depend on 'ltests.h',
which may not even exist.
This commit brings a new implementation for HARDMEMTESTS, which forces
an emergency GC whenever possible. It also fixes some issues detected
with this option:
- A small bug in lvm.c: a closure could be collected by an emergency
GC while being initialized.
- Some tests: a memory address can be immediatly reused after a GC;
for instance, two consecutive '{}' expressions can return exactly the
same address, if the first one is not anchored.
Constants directly assigned to other constants were not propagating:
For instance, in
local <const> k1 = 10
local <const> k2 = k1
'k2' were not treated as a compile-time constant.
String literal expressions have their own kind VKSTR, instead of the
generic VK. This allows strings to "cross" functions without entering
their constant tables (e.g., if they are used only by some nested
function).
An error in a closing method may be caused by a lack of resources,
such as memory or stack space, and the error may free enough resources
(by unwinding the stack) to allow the method to work if called again.
If the closing method is already running after some error (including
its own), it is not called again.
Opcodes OP_NEWTABLE and OP_SETLIST use the same representation to
store the size of the array part of a table. This new representation
can go up to 2^33 (8 + 25 bits).
OP_NEWTABLE is followed by an OP_EXTRAARG, so that it can keep
the exact size of the array part of the table to be created.
(Functions 'luaO_int2fb'/'luaO_fb2int' were removed.)
In the generic for loop, it is simpler for OP_TFORLOOP to use the
same 'ra' as OP_TFORCALL. Moreover, the internal names of the loop
temporaries "(for ...)" don't need to leak internal details (even
because the numerical for loop doesn't have a fixed role for each of
its temporaries).
VLOCAL expressions keep a reference to their corresponding 'Vardesc',
and 'Upvaldesc' (for upvalues) has a field 'ro' (read-only). So, it is
easier to check whether a variable is read-only. The decoupling in
VLOCAL between 'vidx' ('Vardesc' index) and 'sidx' (stack index)
should also help the forthcoming implementation of compile-time
constant propagation.
The syntax for local attributes ('const'/'toclose') was unified with
the regular syntax for local variables, so that we can have variables
with attributes in local definitions with multiple names; for instance:
local <toclose> f, <const> err = io.open(fname)
This new syntax does not implement constant propagation, yet.
This commit also has some small improvements to the manual.
- Better documentation in 'testes/cstack.lua' about using
'debug.setCstacklimit' to find a good limit.
- Constant LUAI_MAXCSTACK gets added CSTACKERR (extra stack for
error handling), so that it is compatible with the argument to
'debug.setCstacklimit'.
- Added a test for calling 'debug.traceback' after yields inside
hooks. (Lua 5.3 seems to have a bug there.)
- Removed test "repeat test with '__open' metamethod instead of a
function", as the previous test already uses the '__open' metamethod.
(It changed when functions were removed as possible to-be-closed
variables).
When there are multiple errors when closing objects, the error
reported by the protected call is the first one, for two reasons:
First, other errors may be caused by this one;
second, the first error is handled in the original execution context,
and therefore has the full traceback.
Instead of a 'tocont' flag, the function 'warn' in Lua now receives all
message pieces as multiple arguments in a single call. Besides being
simpler to use, this implementation ensures that Lua code cannot create
unfinished warnings.
- tests show progress in real time, so that we can see maximum
stack levels even if test crashes.
- new test for recursion continuing into message handler.
- new error message for "attempt to assign to const variable"
- note in the manual about compatibility options
- comments
- small changes in 'read_line' and 'pushstr'
The flag for to-be-closed variables was changed from '*toclose'
to '<toclose>'. Several people found confusing the old syntax and
the new one has a clear terminator, making it more flexible for
future changes.
Back to how it was, a coroutine does not unwind its stack in case of
errors (and therefore do not close its to-be-closed variables). This
allows the stack to be examined after the error. The program can
use 'coroutine.kill' to close the variables.
The function created by 'coroutine.wrap', however, closes the
coroutine's variables in case of errors, as it is impossible to examine
the stack any way.
- 'L' added to the 'BuffFS' structure
- '%c' does not handle control characters (it is not its business.
This now is done by the lexer, who is the one in charge of that
kind of errors.)
- avoid the direct use of 'l_sprintf' in the Lua kernel
Both when setting a path and searching for a file ('searchpath'),
this commit reduces the number of intermediate strings created
in Lua.
(For setting a path the change is not relevant, because this is
done only twice when loading the module. Anyway, it is a nice example
of how to use auxlib buffers to manipulate strings in the C API.)
The function 'luaO_pushvfstring' now uses an internal buffer to
concatenate small strings, instead of pushing all pieces on the
stack. This avoids the creation of several small Lua strings for each
piece of the result. (For instance, a format like "n: '%d'" used to
create three intermediate strings: "n: '", the numeral, and "'".
Now it creates none.)
Avoid creating extra strings when possible:
- avoid creating new resulting string when subject was not modified
(instead, return the subject itself);
- avoid creating strings representing the captured substrings when
handling replacements like '%1' (instead, add the substring directly
to the buffer).
