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First implementation for 'const' variables

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A variable can be declared const, which means it cannot be assigned to,
with the syntax 'local <const> name = exp'.
This commit is contained in:
Roberto Ierusalimschy 2019-05-17 11:11:44 -03:00
parent 347d6961ac
commit d9f40e3f6f
7 changed files with 207 additions and 58 deletions
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20
lcode.c
View File

@ -678,11 +678,12 @@ void luaK_setoneret (FuncState *fs, expdesc *e) {
void luaK_dischargevars (FuncState *fs, expdesc *e) {
switch (e->k) {
case VLOCAL: { /* already in a register */
e->u.info = e->u.var.idx;
e->k = VNONRELOC; /* becomes a non-relocatable value */
break;
}
case VUPVAL: { /* move value to some (pending) register */
e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.var.idx, 0);
e->k = VRELOC;
break;
}
@ -938,12 +939,12 @@ void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {
switch (var->k) {
case VLOCAL: {
freeexp(fs, ex);
exp2reg(fs, ex, var->u.info); /* compute 'ex' into proper place */
exp2reg(fs, ex, var->u.var.idx); /* compute 'ex' into proper place */
return;
}
case VUPVAL: {
int e = luaK_exp2anyreg(fs, ex);
luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
luaK_codeABC(fs, OP_SETUPVAL, e, var->u.var.idx, 0);
break;
}
case VINDEXUP: {
@ -1165,26 +1166,31 @@ static int isSCnumber (expdesc *e, lua_Integer *i, int *isfloat) {
** values in registers.
*/
void luaK_indexed (FuncState *fs, expdesc *t, expdesc *k) {
lua_assert(!hasjumps(t) && (vkisinreg(t->k) || t->k == VUPVAL));
lua_assert(!hasjumps(t) &&
(t->k == VLOCAL || t->k == VNONRELOC || t->k == VUPVAL));
if (t->k == VUPVAL && !isKstr(fs, k)) /* upvalue indexed by non string? */
luaK_exp2anyreg(fs, t); /* put it in a register */
t->u.ind.t = t->u.info; /* register or upvalue index */
if (t->k == VUPVAL) {
t->u.ind.t = t->u.var.idx; /* upvalue index */
t->u.ind.idx = k->u.info; /* literal string */
t->k = VINDEXUP;
}
else if (isKstr(fs, k)) {
else {
/* register index of the table */
t->u.ind.t = (t->k == VLOCAL) ? t->u.var.idx: t->u.info;
if (isKstr(fs, k)) {
t->u.ind.idx = k->u.info; /* literal string */
t->k = VINDEXSTR;
}
else if (isCint(k)) {
t->u.ind.idx = cast_int(k->u.ival); /* integer constant in proper range */
t->u.ind.idx = cast_int(k->u.ival); /* int. constant in proper range */
t->k = VINDEXI;
}
else {
t->u.ind.idx = luaK_exp2anyreg(fs, k); /* register */
t->k = VINDEXED;
}
}
}

113
lparser.c
View File

@ -156,6 +156,13 @@ static void init_exp (expdesc *e, expkind k, int i) {
}
static void init_var (expdesc *e, expkind k, int i) {
e->f = e->t = NO_JUMP;
e->k = k;
e->u.var.idx = i;
}
static void codestring (LexState *ls, expdesc *e, TString *s) {
init_exp(e, VK, luaK_stringK(ls->fs, s));
}
@ -187,31 +194,82 @@ static int registerlocalvar (LexState *ls, TString *varname) {
/*
** Create a new local variable with the given 'name'.
*/
static void new_localvar (LexState *ls, TString *name) {
static Vardesc *new_localvar (LexState *ls, TString *name) {
FuncState *fs = ls->fs;
Dyndata *dyd = ls->dyd;
Vardesc *var;
int reg = registerlocalvar(ls, name);
checklimit(fs, dyd->actvar.n + 1 - fs->firstlocal,
MAXVARS, "local variables");
luaM_growvector(ls->L, dyd->actvar.arr, dyd->actvar.n + 1,
dyd->actvar.size, Vardesc, MAX_INT, "local variables");
dyd->actvar.arr[dyd->actvar.n++].idx = cast(short, reg);
var = &dyd->actvar.arr[dyd->actvar.n++];
var->idx = cast(short, reg);
var->name = name;
var->ro = 0;
return var;
}
#define new_localvarliteral(ls,v) \
new_localvar(ls, luaX_newstring(ls, "" v, (sizeof(v)/sizeof(char)) - 1));
/*
** Return the "variable description" (Vardesc) of a given
** variable
*/
static Vardesc *getlocalvardesc (FuncState *fs, int i) {
return &fs->ls->dyd->actvar.arr[fs->firstlocal + i];
}
/*
** Get the debug-information entry for current variable 'i'.
*/
static LocVar *getlocvar (FuncState *fs, int i) {
int idx = fs->ls->dyd->actvar.arr[fs->firstlocal + i].idx;
int idx = getlocalvardesc(fs, i)->idx;
lua_assert(idx < fs->nlocvars);
return &fs->f->locvars[idx];
}
/*
** Return the "variable description" (Vardesc) of a given
** variable or upvalue
*/
static Vardesc *getvardesc (FuncState *fs, expdesc *e) {
if (e->k == VLOCAL)
return getlocalvardesc(fs, e->u.var.idx);
else if (e->k != VUPVAL)
return NULL; /* not a local variable */
else { /* upvalue: must go up all levels up to the original local */
int idx = e->u.var.idx;
for (;;) {
Upvaldesc *up = &fs->f->upvalues[idx];
fs = fs->prev; /* must look at the previous level */
idx = up->idx; /* at this index */
if (fs == NULL) { /* no more levels? (can happen only with _ENV) */
lua_assert(strcmp(getstr(up->name), LUA_ENV) == 0);
return NULL;
}
else if (up->instack) /* got to the original level? */
return getlocalvardesc(fs, idx);
/* else repeat for previous level */
}
}
}
static void check_readonly (LexState *ls, expdesc *e) {
Vardesc *vardesc = getvardesc(ls->fs, e);
if (vardesc && vardesc->ro) { /* is variable local and const? */
const char *msg = luaO_pushfstring(ls->L,
"assignment to const variable '%s'", getstr(vardesc->name));
luaK_semerror(ls, msg); /* error */
}
}
/*
** Start the scope for the last 'nvars' created variables.
** (debug info.)
@ -259,7 +317,7 @@ static int newupvalue (FuncState *fs, TString *name, expdesc *v) {
while (oldsize < f->sizeupvalues)
f->upvalues[oldsize++].name = NULL;
f->upvalues[fs->nups].instack = (v->k == VLOCAL);
f->upvalues[fs->nups].idx = cast_byte(v->u.info);
f->upvalues[fs->nups].idx = cast_byte(v->u.var.idx);
f->upvalues[fs->nups].name = name;
luaC_objbarrier(fs->ls->L, f, name);
return fs->nups++;
@ -304,7 +362,7 @@ static void singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {
else {
int v = searchvar(fs, n); /* look up locals at current level */
if (v >= 0) { /* found? */
init_exp(var, VLOCAL, v); /* variable is local */
init_var(var, VLOCAL, v); /* variable is local */
if (!base)
markupval(fs, v); /* local will be used as an upval */
}
@ -317,7 +375,7 @@ static void singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {
/* else was LOCAL or UPVAL */
idx = newupvalue(fs, n, var); /* will be a new upvalue */
}
init_exp(var, VUPVAL, idx); /* new or old upvalue */
init_var(var, VUPVAL, idx); /* new or old upvalue */
}
}
}
@ -1199,20 +1257,20 @@ static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
for (; lh; lh = lh->prev) { /* check all previous assignments */
if (vkisindexed(lh->v.k)) { /* assignment to table field? */
if (lh->v.k == VINDEXUP) { /* is table an upvalue? */
if (v->k == VUPVAL && lh->v.u.ind.t == v->u.info) {
if (v->k == VUPVAL && lh->v.u.ind.t == v->u.var.idx) {
conflict = 1; /* table is the upvalue being assigned now */
lh->v.k = VINDEXSTR;
lh->v.u.ind.t = extra; /* assignment will use safe copy */
}
}
else { /* table is a register */
if (v->k == VLOCAL && lh->v.u.ind.t == v->u.info) {
if (v->k == VLOCAL && lh->v.u.ind.t == v->u.var.idx) {
conflict = 1; /* table is the local being assigned now */
lh->v.u.ind.t = extra; /* assignment will use safe copy */
}
/* is index the local being assigned? */
if (lh->v.k == VINDEXED && v->k == VLOCAL &&
lh->v.u.ind.idx == v->u.info) {
lh->v.u.ind.idx == v->u.var.idx) {
conflict = 1;
lh->v.u.ind.idx = extra; /* previous assignment will use safe copy */
}
@ -1222,7 +1280,7 @@ static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
if (conflict) {
/* copy upvalue/local value to a temporary (in position 'extra') */
OpCode op = (v->k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;
luaK_codeABC(fs, op, extra, v->u.info, 0);
luaK_codeABC(fs, op, extra, v->u.var.idx, 0);
luaK_reserveregs(fs, 1);
}
}
@ -1237,6 +1295,7 @@ static void check_conflict (LexState *ls, struct LHS_assign *lh, expdesc *v) {
static void restassign (LexState *ls, struct LHS_assign *lh, int nvars) {
expdesc e;
check_condition(ls, vkisvar(lh->v.k), "syntax error");
check_readonly(ls, &lh->v);
if (testnext(ls, ',')) { /* restassign -> ',' suffixedexp restassign */
struct LHS_assign nv;
nv.prev = lh;
@ -1615,28 +1674,38 @@ static void commonlocalstat (LexState *ls) {
}
static void tocloselocalstat (LexState *ls) {
static void tocloselocalstat (LexState *ls, Vardesc *var) {
FuncState *fs = ls->fs;
TString *attr = str_checkname(ls);
if (strcmp(getstr(attr), "toclose") != 0)
luaK_semerror(ls,
luaO_pushfstring(ls->L, "unknown attribute '%s'", getstr(attr)));
testnext(ls, '>');
new_localvar(ls, str_checkname(ls));
checknext(ls, '=');
exp1(ls);
var->ro = 1; /* to-be-closed variables are always read-only */
markupval(fs, fs->nactvar);
fs->bl->insidetbc = 1; /* in the scope of a to-be-closed variable */
adjustlocalvars(ls, 1);
luaK_codeABC(fs, OP_TBC, fs->nactvar - 1, 0, 0);
}
static void attriblocalstat (LexState *ls) {
Vardesc *var;
TString *attr = str_checkname(ls);
testnext(ls, '>');
var = new_localvar(ls, str_checkname(ls));
checknext(ls, '=');
exp1(ls);
adjustlocalvars(ls, 1);
if (strcmp(getstr(attr), "const") == 0)
var->ro = 1; /* set variable as read-only */
else if (strcmp(getstr(attr), "toclose") == 0)
tocloselocalstat(ls, var);
else
luaK_semerror(ls,
luaO_pushfstring(ls->L, "unknown attribute '%s'", getstr(attr)));
}
static void localstat (LexState *ls) {
/* stat -> LOCAL NAME {',' NAME} ['=' explist]
| LOCAL *toclose NAME '=' exp */
if (testnext(ls, '<'))
tocloselocalstat(ls);
attriblocalstat(ls);
else
commonlocalstat(ls);
}
@ -1801,7 +1870,7 @@ static void mainfunc (LexState *ls, FuncState *fs) {
expdesc v;
open_func(ls, fs, &bl);
setvararg(fs, 0); /* main function is always declared vararg */
init_exp(&v, VLOCAL, 0); /* create and... */
init_var(&v, VLOCAL, 0); /* create and... */
newupvalue(fs, ls->envn, &v); /* ...set environment upvalue */
luaX_next(ls); /* read first token */
statlist(ls); /* parse main body */

13
lparser.h
View File

@ -33,8 +33,8 @@ typedef enum {
VKINT, /* integer constant; nval = numerical integer value */
VNONRELOC, /* expression has its value in a fixed register;
info = result register */
VLOCAL, /* local variable; info = local register */
VUPVAL, /* upvalue variable; info = index of upvalue in 'upvalues' */
VLOCAL, /* local variable; var.idx = local register */
VUPVAL, /* upvalue variable; var.idx = index of upvalue in 'upvalues' */
VINDEXED, /* indexed variable;
ind.t = table register;
ind.idx = key's R index */
@ -58,7 +58,7 @@ typedef enum {
#define vkisvar(k) (VLOCAL <= (k) && (k) <= VINDEXSTR)
#define vkisindexed(k) (VINDEXED <= (k) && (k) <= VINDEXSTR)
#define vkisinreg(k) ((k) == VNONRELOC || (k) == VLOCAL)
typedef struct expdesc {
expkind k;
@ -70,15 +70,20 @@ typedef struct expdesc {
short idx; /* index (R or "long" K) */
lu_byte t; /* table (register or upvalue) */
} ind;
struct { /* for local variables and upvalues */
lu_byte idx; /* index of the variable */
} var;
} u;
int t; /* patch list of 'exit when true' */
int f; /* patch list of 'exit when false' */
} expdesc;
/* description of active local variable */
/* description of an active local variable */
typedef struct Vardesc {
TString *name;
short idx; /* index of the variable in the Proto's 'locvars' array */
lu_byte ro; /* true if variable is 'const' */
} Vardesc;

28
manual/manual.of
View File

@ -1488,13 +1488,24 @@ Function calls are explained in @See{functioncall}.
@sect3{localvar| @title{Local Declarations}
@x{Local variables} can be declared anywhere inside a block.
The declaration can include an initial assignment:
The declaration can include an initialization:
@Produc{
@producname{stat}@producbody{@Rw{local} namelist @bnfopt{@bnfter{=} explist}}
}
@producname{stat}@producbody{
@Rw{local} @bnfter{<} Name @bnfter{>} Name @bnfter{=} exp
}}
If present, an initial assignment has the same semantics
of a multiple assignment @see{assignment}.
Otherwise, all variables are initialized with @nil.
The second syntax declares a local with a given attribute,
which is the name between the angle brackets.
In this case, there must be an initialization.
There are two possible attributes:
@id{const}, which declares a @x{constant variable},
that is, a variable that cannot be assigned to
after its initialization;
and @id{toclose}, wich declares a to-be-closed variable @see{to-be-closed}.
A chunk is also a block @see{chunks},
and so local variables can be declared in a chunk outside any explicit block.
@ -1506,12 +1517,12 @@ The visibility rules for local variables are explained in @See{visibility}.
@sect3{to-be-closed| @title{To-be-closed Variables}
A local variable can be declared as a @def{to-be-closed} variable,
with the following syntax:
using the identifier @id{toclose} as its attribute:
@Produc{
@producname{stat}@producbody{
@Rw{local} @bnfter{<} @bnfter{toclose} @bnfter{>} Name @bnfter{=} exp
@Rw{local} @bnfter{<} @id{toclose} @bnfter{>} Name @bnfter{=} exp
}}
A to-be-closed variable behaves like a normal local variable,
A to-be-closed variable behaves like a constant local variable,
except that its value is @emph{closed} whenever the variable
goes out of scope, including normal block termination,
exiting its block by @Rw{break}/@Rw{goto}/@Rw{return},
@ -7603,7 +7614,7 @@ or a float otherwise.
@LibEntry{math.abs (x)|
Returns the absolute value of @id{x}. (integer/float)
Returns the maximum value between @id{x} and @id{-x}. (integer/float)
}
@ -8042,7 +8053,8 @@ following the lexical conventions of Lua.
This format always reads the longest input sequence that
is a valid prefix for a numeral;
if that prefix does not form a valid numeral
(e.g., an empty string, @St{0x}, or @St{3.4e-}),
(e.g., an empty string, @St{0x}, or @St{3.4e-})
or it is too long (more than 200 characters),
it is discarded and the format returns @nil.
}
@ -8949,7 +8961,7 @@ and @bnfNter{LiteralString}, see @See{lexical}.)
@OrNL @Rw{function} funcname funcbody
@OrNL @Rw{local} @Rw{function} @bnfNter{Name} funcbody
@OrNL @Rw{local} namelist @bnfopt{@bnfter{=} explist}
@OrNL @Rw{local} @bnfter{<} @bnfter{toclose} @bnfter{>} Name @bnfter{=} exp
@OrNL @Rw{local} @bnfter{<} Name @bnfter{>} Name @bnfter{=} exp
}
@producname{retstat}@producbody{@Rw{return}

61
testes/constructs.lua
View File

@ -59,6 +59,41 @@ assert((x>y) and x or y == 2);
assert(1234567890 == tonumber('1234567890') and 1234567890+1 == 1234567891)
do -- testing operators with diffent kinds of constants
-- operands to consider:
-- * fit in register
-- * constant doesn't fit in register
-- * floats with integral values
local operand = {3, 100, 5.0, -10, -5.0, 10000, -10000}
local operator = {"+", "-", "*", "/", "//", "%", "^",
"&", "|", "^", "<<", ">>",
"==", "~=", "<", ">", "<=", ">=",}
for _, op in ipairs(operator) do
local f = assert(load(string.format([[return function (x,y)
return x %s y
end]], op)))();
for _, o1 in ipairs(operand) do
for _, o2 in ipairs(operand) do
local gab = f(o1, o2)
_ENV.XX = o1
code = string.format("return XX %s %s", op, o2)
res = assert(load(code))()
assert(res == gab)
_ENV.XX = o2
local code = string.format("return (%s) %s XX", o1, op)
local res = assert(load(code))()
assert(res == gab)
code = string.format("return (%s) %s %s", o1, op, o2)
res = assert(load(code))()
assert(res == gab)
end
end
end
end
-- silly loops
repeat until 1; repeat until true;
@ -175,6 +210,28 @@ assert(a==1 and b==nil)
print'+';
do -- testing constants
local <const> prog = [[local <XXX> x = 10]]
checkload(prog, "unknown attribute 'XXX'")
checkload([[local <const> xxx = 20; xxx = 10]],
":1: assignment to const variable 'xxx'")
checkload([[
local xx;
local <const> xxx = 20;
local yyy;
local function foo ()
local abc = xx + yyy + xxx;
return function () return function () xxx = yyy end end
end
]], ":6: assignment to const variable 'xxx'")
checkload([[
local <toclose> x = nil
x = io.open()
]], ":2: assignment to const variable 'x'")
end
f = [[
return function ( a , b , c , d , e )
@ -245,12 +302,12 @@ print('testing short-circuit optimizations (' .. _ENV.GLOB1 .. ')')
-- operators with their respective values
local binops = {
local <const> binops = {
{" and ", function (a,b) if not a then return a else return b end end},
{" or ", function (a,b) if a then return a else return b end end},
}
local cases = {}
local <const> cases = {}
-- creates all combinations of '(cases[i] op cases[n-i])' plus
-- 'not(cases[i] op cases[n-i])' (syntax + value)

8
testes/files.lua
View File

@ -144,7 +144,7 @@ do
f:write(string.format("0x%X\n", -maxint))
f:write("-0xABCp-3", '\n')
assert(f:close())
f = assert(io.open(file, "r"))
local <toclose> f = assert(io.open(file, "r"))
assert(f:read("n") == maxint)
assert(f:read("n") == maxint)
assert(f:read("n") == 0xABCp-3)
@ -170,18 +170,18 @@ three
]]
local l1, l2, l3, l4, n1, n2, c, dummy
assert(f:close())
f = assert(io.open(file, "r"))
local <toclose> f = assert(io.open(file, "r"))
l1, l2, n1, n2, dummy = f:read("l", "L", "n", "n")
assert(l1 == "a line" and l2 == "another line\n" and
n1 == 1234 and n2 == 3.45 and dummy == nil)
assert(f:close())
f = assert(io.open(file, "r"))
local <toclose> f = assert(io.open(file, "r"))
l1, l2, n1, n2, c, l3, l4, dummy = f:read(7, "l", "n", "n", 1, "l", "l")
assert(l1 == "a line\n" and l2 == "another line" and c == '\n' and
n1 == 1234 and n2 == 3.45 and l3 == "one" and l4 == "two"
and dummy == nil)
assert(f:close())
f = assert(io.open(file, "r"))
local <toclose> f = assert(io.open(file, "r"))
-- second item failing
l1, n1, n2, dummy = f:read("l", "n", "n", "l")
assert(l1 == "a line" and n1 == nil)

6
testes/math.lua
View File

@ -3,10 +3,10 @@
print("testing numbers and math lib")
local minint = math.mininteger
local maxint = math.maxinteger
local <const> minint = math.mininteger
local <const> maxint = math.maxinteger
local intbits = math.floor(math.log(maxint, 2) + 0.5) + 1
local <const> intbits = math.floor(math.log(maxint, 2) + 0.5) + 1
assert((1 << intbits) == 0)
assert(minint == 1 << (intbits - 1))