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'break' coded as 'goto' + small bug when closing multiple gotos

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This commit is contained in:
Roberto Ierusalimschy 2011-02-10 12:50:41 -02:00
parent 3f5b56c48b
commit bf8b08295a
1 changed files with 52 additions and 59 deletions
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111
lparser.c
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@ -1,5 +1,5 @@
/*
** $Id: lparser.c,v 2.102 2011/02/09 16:51:28 roberto Exp roberto $
** $Id: lparser.c,v 2.103 2011/02/09 17:03:18 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/
@ -41,7 +41,6 @@
*/
typedef struct BlockCnt {
struct BlockCnt *previous; /* chain */
int breaklist; /* list of jumps out of this loop */
int firstlabel; /* index of first label in this block */
int firstgoto; /* index of first pending goto in this block */
lu_byte nactvar; /* # active locals outside the block */
@ -380,16 +379,31 @@ static int findlabel (LexState *ls, int g) {
}
static int newlabelentry (LexState *ls, Labellist *l, TString *name,
int line, int pc) {
int n = l->n;
luaM_growvector(ls->L, l->arr, n, l->size, Labeldesc, MAX_INT, "labels");
l->arr[n].name = name;
l->arr[n].line = line;
l->arr[n].nactvar = ls->fs->nactvar;
l->arr[n].pc = pc;
l->n++;
return n;
}
/*
** check whether new label 'lb' matches any pending goto in current
** check whether new label 'lb' matches any pending gotos in current
** block; solves forward jumps
*/
static void findgotos (LexState *ls, Labeldesc *lb) {
int i;
Dyndata *dyd = ls->dyd;
for (i = ls->fs->bl->firstgoto; i < dyd->gt.n; i++) {
int i = ls->fs->bl->firstgoto;
while (i < dyd->gt.n) {
if (eqstr(dyd->gt.arr[i].name, lb->name))
closegoto(ls, i, lb);
else
i++;
}
}
@ -419,7 +433,6 @@ static void movegotosout (FuncState *fs, BlockCnt *bl) {
static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
bl->breaklist = NO_JUMP;
bl->isloop = isloop;
bl->nactvar = fs->nactvar;
bl->firstlabel = fs->ls->dyd->label.n;
@ -431,30 +444,48 @@ static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
}
/*
** create a label named "break" to resolve break statements
*/
static void breaklabel (LexState *ls) {
TString *n = luaS_new(ls->L, "break");
int l = newlabelentry(ls, &ls->dyd->label, n, 0, ls->fs->pc);
findgotos(ls, &ls->dyd->label.arr[l]);
}
/*
** generates an error for an undefined 'goto'; choose appropriate
** message when label name is a resserved word (which can only be 'break')
*/
static void undefgoto (LexState *ls, Labeldesc *gt) {
const char *msg = (gt->name->tsv.reserved > 0)
? "<%s> at line %d not inside a loop"
: "label " LUA_QS " (<goto> at line %d) undefined";
msg = luaO_pushfstring(ls->L, msg, getstr(gt->name), gt->line);
semerror(ls, msg);
}
static void leaveblock (FuncState *fs) {
BlockCnt *bl = fs->bl;
LexState *ls = fs->ls;
fs->bl = bl->previous;
removevars(fs, bl->nactvar);
ls->dyd->label.n = bl->firstlabel; /* remove local labels */
if (bl->previous) /* inner block? */
movegotosout(fs, bl); /* update pending gotos to outer block */
else if (bl->firstgoto < ls->dyd->gt.n) { /* pending gotos in outer block? */
Labeldesc *gt = &ls->dyd->gt.arr[bl->firstgoto];
const char *msg = luaO_pushfstring(ls->L,
"label " LUA_QS " (<goto> at line %d) undefined",
getstr(gt->name), gt->line);
semerror(ls, msg);
}
if (bl->previous && bl->upval) {
/* create a 'jump to here' to close upvalues */
int j = luaK_jump(fs);
luaK_patchclose(fs, j, bl->nactvar);
luaK_patchtohere(fs, j);
}
if (bl->isloop)
breaklabel(ls); /* close pending breaks */
fs->bl = bl->previous;
removevars(fs, bl->nactvar);
lua_assert(bl->nactvar == fs->nactvar);
fs->freereg = fs->nactvar; /* free registers */
luaK_patchtohere(fs, bl->breaklist);
ls->dyd->label.n = bl->firstlabel; /* remove local labels */
if (bl->previous) /* inner block? */
movegotosout(fs, bl); /* update pending gotos to outer block */
else if (bl->firstgoto < ls->dyd->gt.n) /* pending gotos in outer block? */
undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]); /* error */
}
@ -1070,7 +1101,6 @@ static void block (LexState *ls) {
BlockCnt bl;
enterblock(fs, &bl, 0);
statlist(ls);
lua_assert(bl.breaklist == NO_JUMP);
leaveblock(fs);
}
@ -1159,44 +1189,6 @@ static int cond (LexState *ls) {
}
/* code a break statement. The last 'if' decides the need to close
upvalues when leaving the block. If the block has upvalues, it
must be closed. If it has local variables and any label
before the break, those variables must be closed too, as they
may be used as upvalues after the break and through a goto
be exited through this break.
*/
static void breakstat (LexState *ls) {
FuncState *fs = ls->fs;
BlockCnt *bl = fs->bl;
int upval = 0;
while (bl && !bl->isloop) {
upval |= bl->upval;
bl = bl->previous;
}
if (!bl)
semerror(ls, "no loop to break");
luaK_concat(fs, &bl->breaklist, luaK_jump(fs));
if (upval ||
(fs->nactvar > bl->nactvar &&
ls->dyd->label.n > bl->firstlabel))
luaK_patchclose(fs, bl->breaklist, bl->nactvar);
}
static int newlabelentry (LexState *ls, Labellist *l, TString *name,
int line, int pc) {
int n = l->n;
luaM_growvector(ls->L, l->arr, l->n, l->size, Labeldesc, MAX_INT, "labels");
l->arr[n].name = name;
l->arr[n].line = line;
l->arr[n].nactvar = ls->fs->nactvar;
l->arr[n].pc = pc;
l->n++;
return n;
}
static void gotostat (LexState *ls, TString *label, int line) {
/* create new entry for this goto */
int g = newlabelentry(ls, &ls->dyd->gt, label, line, luaK_jump(ls->fs));
@ -1551,7 +1543,8 @@ static int statement (LexState *ls) {
}
case TK_BREAK: { /* stat -> breakstat */
luaX_next(ls); /* skip BREAK */
breakstat(ls);
/* code it as "goto 'break'" */
gotostat(ls, luaS_new(ls->L, "break"), line);
return 1; /* must be last statement */
}
case TK_GOTO: { /* stat -> 'goto' NAME */