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jumps in 'for' loops don't need to be signed

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This commit is contained in:
Roberto Ierusalimschy
2017-08-14 15:33:14 -03:00
parent f185c0132e
commit ac65bab25f
4 changed files with 38 additions and 20 deletions
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30
lparser.c
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@@ -1,5 +1,5 @@
/*
** $Id: lparser.c,v 2.162 2017/06/29 15:38:41 roberto Exp roberto $
** $Id: lparser.c,v 2.163 2017/08/12 13:12:21 roberto Exp roberto $
** Lua Parser
** See Copyright Notice in lua.h
*/
@@ -1307,6 +1307,22 @@ static int exp1 (LexState *ls) {
}
/*
** Fix for instruction at position 'pc' to jump to 'dest'.
** (Jump addresses are relative in Lua). 'back' true means
** a back jump.
*/
static void fixforjump (FuncState *fs, int pc, int dest, int back) {
Instruction *jmp = &fs->f->code[pc];
int offset = dest - (pc + 1);
if (back)
offset = -offset;
if (offset > MAXARG_Bx)
luaX_syntaxerror(fs->ls, "control structure too long");
SETARG_Bx(*jmp, offset);
}
static void forbody (LexState *ls, int base, int line, int nvars, int isnum) {
/* forbody -> DO block */
BlockCnt bl;
@@ -1314,21 +1330,23 @@ static void forbody (LexState *ls, int base, int line, int nvars, int isnum) {
int prep, endfor;
adjustlocalvars(ls, 3); /* control variables */
checknext(ls, TK_DO);
prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);
prep = isnum ? luaK_codeABx(fs, OP_FORPREP, base, 0) : luaK_jump(fs);
enterblock(fs, &bl, 0); /* scope for declared variables */
adjustlocalvars(ls, nvars);
luaK_reserveregs(fs, nvars);
block(ls);
leaveblock(fs); /* end of scope for declared variables */
luaK_patchtohere(fs, prep);
if (isnum) /* numeric for? */
endfor = luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP);
if (isnum) { /* numeric for? */
fixforjump(fs, prep, luaK_getlabel(fs), 0);
endfor = luaK_codeABx(fs, OP_FORLOOP, base, 0);
}
else { /* generic for */
luaK_patchtohere(fs, prep);
luaK_codeABC(fs, OP_TFORCALL, base, 0, nvars);
luaK_fixline(fs, line);
endfor = luaK_codeAsBx(fs, OP_TFORLOOP, base + 2, NO_JUMP);
}
luaK_patchlist(fs, endfor, prep + 1);
fixforjump(fs, endfor, prep + 1, 1);
luaK_fixline(fs, line);
}