When reinserting elements into a table during a rehash, the code does
not need to invoke all the complexity of a full 'luaH_set':
- The table has space for all keys.
- The key cannot exist in the new hash.
- The keys are valid (not NaN nor nil).
- The keys are normalized (1.0 -> 1).
- The values cannot be nil.
- No barrier needed (the table already pointed to the key and value).
The array at the end of a Lua closure has pointers to upvalues, not
to tagged values. This bug cannot cause any issue: The ISO C standard
requires that all pointers to structures have the same representation,
so sizeof(TValue*) must be equal to sizeof(UpVal*).
Instead of using 'alimit' for keeping the size of the array and at
the same time being a hint for '#t', a table now keeps these two
values separate. The Table structure has a field 'asize' with the
size of the array, while the length hint is kept in the array itself.
That way, tables with no array part waste no space with that field.
Moreover, the space for the hint may have zero cost for small arrays,
if the array of tags plus the hint still fits in a single word.
'debug.getinfo' can return number of extra arguments added to a call by
a chain of __call metavalues. That information is being used to improve
error messages about errors in these extra arguments.
Without this extra space, sequences of insertions/deletions (and
some other uses) can have unpexpected low performances. See the
added tests for an example, and *Mathematical Models to Analyze Lua
Hybrid Tables and Why They Need a Fix* (Martínez, Nicaud, Rotondo;
arXiv:2208.13602v2) for detais.
Array part needs 1/3 of its elements filled, instead of 1/2.
Array entries use ~1/3 the memory of hash entries, so this new rule
still ensures that array parts do not use more memory than keeping
the values in the hash, while allowing more uses of the array part,
which is more efficient than the hash.
If there are no integer keys outside the array part, there is no
reason to resize it, saving the time to count its elements. Moreover,
assignments to non-integer keys will not collapse a table created with
'table.create'.
Any call to 'va_start' must have a corresponding call to 'va_end';
so, functions called between them (luaO_pushvfstring in particular)
cannot raise errors.
Any call to 'va_start' must have a corresponding call to 'va_end';
so, functions called between them (luaO_pushvfstring in particular)
cannot raise errors.
The use of a pointer (not access, only for computations) after its
deallocation is forbiden in ISO C, but seems to work fine in all
platforms we are aware of. So, using that to correct stack pointers
after a stack reallocation seems safe and is much simpler than the
current implementation (first change all pointers to offsets and
then changing the offsets back to pointers). Anyway, for now that
option is disabled.
In function 'luaK_exp2val', used to generate code for indices: Macro
'hasjumps' does not consider the case when the whole expression is a
"jump" (a test). In all other of its uses, the surrounding code ensures
that the expression cannot be VJMP.
Conversion float->string ensures that, for any float f,
tonumber(tostring(f)) == f, but still avoiding noise like 1.1
converting to "1.1000000000000001".
That reduces the size of "CallInfo". Moreover, bit CIST_HOOKED from
call status is not needed. When in a hook, 'transferinfo' is always
valid, being zero when the hook is not call/return.
The parameter 'nresults' in 'lua_call' and similar functions has a
limit of 250. It already had an undocumented (and unchecked) limit of
SHRT_MAX, but it is seldom larger than 2.
Therefore, fields ftransfer/ntransfer in lua_Debug must have type
'int'. (Maximum stack size must fit in an 'int'.) Also, this commit
adds check that maximum stack size respects size_t for size in bytes.
