--- C:/dev/luas/lua-5.2.0/src/lparser.c Fri Dec 2 05:23:56 2011 +++ C:/dev/luas/lua-5.2.0/src/lparser_safe2.c Sun Mar 3 21:44:22 2013 @@ -900,7 +900,44 @@ } } +static void safe_navigation(LexState *ls, expdesc *v) { + FuncState *fs = ls->fs; + luaX_next(ls); + luaK_exp2nextreg(fs, v); + luaK_codeABC(fs,OP_TEST, v->u.info, NO_REG, 0 ); + { + int old_free=fs->freereg; + int vreg=v->u.info; + int j = luaK_codeAsBx(fs, OP_JMP, 0, NO_JUMP); + expdesc key; + switch(ls->t.token) { + case '[': + yindex(ls, &key); + luaK_indexed(fs, v, &key); + luaK_exp2nextreg(fs, v); + break; + case '.': + luaX_next(ls); + checkname(ls, &key); + luaK_indexed(fs, v, &key); + break; + default: + luaX_syntaxerror(ls, "unexpected symbol"); + } + luaK_exp2nextreg(fs, v); + fs->freereg=old_free; + /* i think this check is unnecessary, as any complex key + expressions should be courteous enough to leave the top of + the stack where they found it. */ + if(v->u.info!=vreg) { + luaK_codeABC(fs,OP_MOVE, vreg, v->u.info, 0 ); + v->u.info=vreg; + } + SETARG_sBx(fs->f->code[j], fs->pc-j-1); + } +} + static void primaryexp (LexState *ls, expdesc *v) { /* primaryexp -> prefixexp { `.' NAME | `[' exp `]' | `:' NAME funcargs | funcargs } */ @@ -909,6 +946,10 @@ prefixexp(ls, v); for (;;) { switch (ls->t.token) { + case '?': { /* safe navigation */ + safe_navigation(ls, v); + break; + } case '.': { /* fieldsel */ fieldsel(ls, v); break;