- 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.)
