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).
This commit detaches the number of active variables from the
number of variables in the stack, during compilation. Soon,
compile-time constants will be propagated and therefore will
not exist during run time (in the stack).
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.
In the 'io' library, changed the use of the metatable also as its
own "method table", so that metamethods cannot be accessed as if they
were methods. (For instance, 'io.stdin.__gc' does not result in
the finalizer metamethod anymore.)
- 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).
Removed the field 'name' from the structure 'Vardesc', as the name
of the local variable is already available in the prototype of the
function, through the index 'idx'.
Ensure that operation macros, such as 'luai_numdiv' and 'luai_numidiv',
operate only on variables, or at most at 's2v(ra)'. ('s2v' is a nop, a
cast from pointer to pointer.)
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.
'luaL_traceback' changed to use an aux buffer instead of concats.
This should reduce the quantity of garbage it generates (in the
form of intermediate strings) while producing a trackback.
It also added information about the number of levels skipped when
skipping levels in a trace.
- 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 preprocessor must work with at least 'long', and therefore must
do shifts of up to 31 bits correctly.
- Whenever possible, use unsigned types in shifts.
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.)
To-be-closed variables in C use 'ci.nresults' to code that there is
a variable to be closed in that function. The intialization of the
base C level (the one "running" when calling API functions outside
any Lua call) did not initialize 'ci.nresults', creating (correct)
warnings in valgrind.
Added a new function 'luaL_addgsub', similar to 'luaL_gsub' but that
adds its result directly to a preexisting buffer, avoiding the creation
of one extra intermediate string. Also added two simple macros,
'luaL_bufflen' and 'luaL_buffaddr', to query the current length
and the contents address of a buffer.
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.)
The result of "string.format("%.99f", -1e308) is 410 characters long,
but all other formats have much smaller limits (at most 99 plus a fex
extras). This commit avoids 'string.format' asking for a buffer
~400 chars large when ~100 will do.
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).
This new field gets the length of 'source' in the same structure.
Unlike the other strings in that structure, 'source' can be
relatively large, and Lua already has its length readily available.
The 'GCSenteratomic' is just an auxiliary state for transitioning
to 'GCSatomic'. All GC traversals should be done either on the
'GCSpropagate' state or the 'GCSatomic' state.
Checks of the form '1 <= x && x <= M' were rewritten in the form
'(unsigned)x - 1 < (unsigned)M', which is usually more efficient.
(Other similar checks have similar translations.) Although
some compilers do these optimizations, that does not happen
for all compilers or all cases.
The limit LUAI_MAXCCALLS was renamed LUAI_MAXCSTACK, which better
represents its meaning. Moreover, its definition was moved to
'luaconf.h', given its importance now that Lua does not use
a "stackless" implementation.
- In 'readutf8esc' (llex.c), the overflow check must be done before
shifting the accumulator. It was working because tests were using
64-bit longs. Failed with 32-bit longs.
- In OP_FORPREP (lvm.c), avoid negating an unsigned value. Visual
Studio gives a warning for that operation, despite being well
defined in ISO C.
- In 'luaV_execute' (lvm.c), 'cond' can be defined only when needed,
like all other variables.
When calling metamethods for things like 'a < 3.0', which generates
the opcode OP_LTI, the C register tells that the operand was
converted to an integer, so that it can be corrected to float when
calling a metamethod.
This commit also includes some other stuff:
- file 'onelua.c' added to the project
- opcode OP_PREPVARARG renamed to OP_VARARGPREP
- comparison opcodes rewritten through macros
Changed some implementation details; in particular, it is back using
an internal variable to keep the index, with the control variable
being only a copy of that internal variable. (The direct use of
the control variable demands a check of its type for each access,
which offsets the gains from the use of a single variable.)
- LUAC_VERSION is equal to LUA_VERSION_NUM, and it is stored
as an int.
- 'sizeof(int)' and 'sizeof(size_t)' removed from the header, as
the binary format does not depend on these sizes. (It uses its
own serialization for unsigned integer values.)
The numerical 'for' loop over integers now uses a precomputed counter
to control its number of iteractions. This change eliminates several
weird cases caused by overflows (wrap-around) in the control variable.
(It also ensures that every integer loop halts.)
Also, the special opcodes for the usual case of step==1 were removed.
(The new code is already somewhat complex for the usual case,
but efficient.)
All UTF-8 encoding functionality (including the escape
sequence '\u') accepts all values from the original UTF-8
specification (with sequences of up to six bytes).
By default, the decoding functions in the UTF-8 library do not
accept invalid Unicode code points, such as surrogates. A new
parameter 'nonstrict' makes them accept all code points up to
(2^31)-1, as in the original UTF-8 specification.
- The warning functions get an extra parameter that tells whether
message is to be continued (instead of using end-of-lines as a signal).
- The user data for the warning function is a regular value, instead
of a writable slot inside the Lua state.
When called with no arguments, 'math.randomseed' uses time and ASLR
to generate a somewhat random seed. the initial seed when Lua starts
is generated this way.
Removed code to ensure that strings inside Lua (as returned by
'lua_tolstring') always start in fully aligned addresses.
Since version 5.3 the documentation does not ensure that.
Several small improvements (code style, warnings, comments, more tests),
in particular:
- 'lua_topointer' extended to handle strings
- raises an error in 'string.format("%10q")' ('%q' with modifiers)
- in the manual for 'string.format', the term "option" replaced by
"conversion specifier" (the term used by the C standard)
After a major bad collection (one that collects too few objects),
next collection will be major again. In that case, avoid switching
back to generational mode (as it will have to switch again to
incremental to do next major collection).
The function 'string.gmatch' now has an optional 'init' argument,
similar to 'string.find' and 'string.match'. Moreover, there was
some reorganization in the manipulation of indices in the string
library.
This commit also includes small janitorial work in the manual
and in comments in the interpreter loop.
To-be-closed variables must contain objects with '__toclose'
metamethods (or nil). Functions were removed for several reasons:
* Functions interact badly with sandboxes. If a sandbox raises
an error to interrupt a script, a to-be-closed function still
can hijack control and continue running arbitrary sandboxed code.
* Functions interact badly with coroutines. If a coroutine yields
and is never resumed again, its to-be-closed functions will never
run. To-be-closed objects, on the other hand, will still be closed,
provided they have appropriate finalizers.
* If you really need a function, it is easy to create a dummy
object to run that function in its '__toclose' metamethod.
This comit also adds closing of variables in case of panic.
* unification of the 'nny' and 'nCcalls' counters;
* external C functions ('lua_CFunction') count more "slots" in
the C stack (to allow for their possible use of buffers)
* added a new test script specific for C-stack overflows. (Most
of those tests were already present, but concentrating them
in a single script easies the task of checking whether
'LUAI_MAXCCALLS' is adequate in a system.)
The script 'all', to run all tests, automatically ensures that the
Lua interpreter and the test C libraries (in 'testes/libs/') are
updated with any changes in 'luaconf.h'.
This file is not part of the regular tests. It tests error conditions
that demand too much memory or too much time to create:
* string with too many characters
* control structure with body too large
* chunk with too many lines
* identifier with too many characters
* chunks with too many instructions
* function with too many constants
* too many strings internalized
* table with too many entries
In machines with limited memory (less than 150 GB), many tests run up
to a "not enough memory" error. We need some memory (~256 GB) to
run all tests up to their intrinsic limits.
A long bracket with too many equal signs can overflow the 'int' used for
the counting and some arithmetic done on the value. Changing the counter
to 'size_t' avoids that. (Because what is counted goes to a buffer, an
overflow in the counter will first raise a buffer-overflow error.)
New functions to reset/kill a thread/coroutine, mainly (only?) to
close any pending to-be-closed variable. ('lua_resetthread' also
allows a thread to be reused...)
- in 'luaB_tonumber', do not need to "checkany" when argument
is a number.
- in 'lua_resume', the call to 'luaD_rawrunprotected' cannot return
a status equal to -1.
The call 'math.rand()' converts the higher bits of the internal unsigned
integer random to a float, instead of its lower bits. That ensures that
Lua compiled with different float precisions always generates equal (up
to the available precision) random numbers when given the same seed.
New auxiliary functions/macros 'luaL_argexpected'/'luaL_typeerror'
ease the creation of error messages such as
bad argument #2 to 'setmetatable' (nil or table expected, got boolean)
(The novelty being the "got boolean" part...)
A to-be-closed variable must be closed when a block ends, so even
a 'return foo()' cannot directly returns the results of 'foo'; the
function must close the scope before returning.
It is an error for a to-be-closed variable to have a non-closable
non-nil value when it is being closed. This situation does not seem to
be useful and often hints to an error. (Particularly in the C API, it is
easy to change a to-be-closed index by mistake.)
To remove a to-be-closed variable from the stack in the C API a
function must use 'lua_settop' or 'lua_pop'. Previous implementation of
'luaL_pushresult' was not closing the box. (This commit also added
tests to check that box is being closed "as soon as possible".)
(Long time without testing with '-DHARDSTACKTESTS'...)
With the introduction of to-be-closed variables, calls to 'luaF_close'
can move the stack, but some call sites where keeping pointers to the
stack without correcting them.
Added opcodes for all seven arithmetic operators with K operands
(that is, operands that are numbers in the array of constants of
the function). They cover the cases of constant float operands
(e.g., 'x + .0.0', 'x^0.5') and large integer operands (e.g.,
'x % 10000').
The visibility for functions marked as LUAI_FUNC was changed from
"hidden" to "internal". These functions cannot be called from
outside the Lua kernel, and "internal" visibility offers more
chances for optimizations.
Sometimes it is useful to mark to-be-closed an index that is not
at the top of the stack (e.g., if the value to be closed came from
a function call returning multiple values).
The variable to be closed in a generic 'for' loop now is the
4th value produced in the loop initialization, instead of being
the loop state (the 2nd value produced). That allows a loop to
use a state with a '__toclose' metamethod but do not close it.
(As an example, 'f:lines()' might use the file 'f' as a state
for the loop, but it should not close the file when the loop ends.)
