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281 lines
12 KiB
281 lines
12 KiB
/*
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** $Id: lparser.h,v 1.76.1.1 2017/04/19 17:20:42 roberto Exp $
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** Lua Parser
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** See Copyright Notice in lua.h
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*/
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#ifndef lparser_h
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#define lparser_h
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#include "llimits.h"
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#include "lobject.h"
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#include "lzio.h"
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/*
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** Expression and variable descriptor.
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** Code generation for variables and expressions can be delayed to allow
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** optimizations; An 'expdesc' structure describes a potentially-delayed
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** variable/expression. It has a description of its "main" value plus a
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** list of conditional jumps that can also produce its value (generated
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** by short-circuit operators 'and'/'or').
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*/
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/* kinds of variables/expressions */
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typedef enum {
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VVOID, /* when 'expdesc' describes the last expression a list,
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this kind means an empty list (so, no expression) */
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VNIL, /* constant nil */
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VTRUE, /* constant true */
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VFALSE, /* constant false */
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VK, /* constant in 'k'; info = index of constant in 'k' */
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VKFLT, /* floating constant; nval = numerical float value */
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VKINT, /* integer constant; nval = numerical integer value */
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VNONRELOC, /* expression has its value in a fixed register;
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info = result register */
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VLOCAL, /* local variable; info = local register */
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VUPVAL, /* upvalue variable; info = index of upvalue in 'upvalues' */
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VINDEXED, /* indexed variable;
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ind.vt = whether 't' is register or upvalue;
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ind.t = table register or upvalue;
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ind.idx = key's R/K index */
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VJMP, /* expression is a test/comparison;
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info = pc of corresponding jump instruction */
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VRELOCABLE, /* expression can put result in any register;
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info = instruction pc
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op code may be OP_CLOSURE,OP_NEWTABLE,OP_CONCAT,OP_GETUPVAL,
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OP_GETTABUP,OP_GETTABLE,OP_NOT,Code for binary and unary expressions
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that produce values (arithmetic operations, bitwise operations,
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concat, length)
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*/
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VCALL, /* expression is a function call; info = instruction pc */
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VVARARG /* vararg expression; info = instruction pc */
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} expkind;
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#define vkisvar(k) (VLOCAL <= (k) && (k) <= VINDEXED)
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#define vkisinreg(k) ((k) == VNONRELOC || (k) == VLOCAL)
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typedef struct expdesc {
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expkind k;
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union {
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lua_Integer ival; /* for VKINT */
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lua_Number nval; /* for VKFLT */
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int info; /* for generic use */
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struct { /* for indexed variables (VINDEXED) */
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short idx; /* index (R/K) */
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lu_byte t; /* table (register or upvalue) */
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lu_byte vt; /* whether 't' is register (VLOCAL) or upvalue (VUPVAL) */
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lu_byte key_ravi_type; /* RAVI change: key type */
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TString *usertype; /* RAVI change: usertype name */
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} ind;
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} u;
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int t; /* patch list of 'exit when true' */
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int f; /* patch list of 'exit when false' */
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lu_byte ravi_type; /* RAVI change: type of the expression if known, else RAVI_TANY */
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TString *usertype; /* RAVI change: usertype name */
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int pc; /* RAVI change: holds the program counter for OP_NEWTABLE instruction when a constructor expression is parsed */
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} expdesc;
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/* description of active local variable */
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typedef struct Vardesc {
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short idx; /* variable index in stack */
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} Vardesc;
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/* description of pending goto statements and label statements */
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typedef struct Labeldesc {
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TString *name; /* label identifier */
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int pc; /* position in code */
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int line; /* line where it appeared */
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lu_byte nactvar; /* local level where it appears in current block */
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} Labeldesc;
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/* list of labels or gotos */
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typedef struct Labellist {
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Labeldesc *arr; /* array */
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int n; /* number of entries in use */
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int size; /* array size */
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} Labellist;
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/* dynamic structures used by the parser */
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typedef struct Dyndata {
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/* The actvar structure appears to represent the stack. It is used
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* in a single parsing run - as part of an implicit function that
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* wraps the parsed code. As the code is parsed the stack grows and
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* shrinks.
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*/
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struct { /* list of active local variables */
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Vardesc *arr;
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int n; /* tracks the top of the stack where the next item will go */
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int size; /* number of arr objects allocated (memory) */
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} actvar;
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Labellist gt; /* list of pending gotos */
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Labellist label; /* list of active labels */
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} Dyndata;
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/* control of blocks */
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struct BlockCnt; /* defined in lparser.c */
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/* State needed to generate code for a given function.
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Functions have a register window on the stack.
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The stack is represented in LexState->dyd.actvar (Dyndata)
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structure (see llex.h). The register window of the function
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starts from LexState->dyd.actvar.arr[firstlocal].
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The 'active' local variables of the function extend
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upto LexState->dyd.actvar.arr[nactvar-1].
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Note that when parsing a 'local' declaration statement
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the 'nactvar' is adjusted at the end of the statement
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so that during parsing of the statement the 'nactvar'
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covers locals upto the start of the statement. This means that
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local variables come into scope (become 'active') after
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the local statement ends. However, if the local statement
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defines a function then the variable becomes 'active'
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before the function body is parsed.
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A tricky thing to note is that while 'nactvar' is adjusted
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at the end of the statement - the 'stack' as represented
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by LexState->dyd.actvar.arr is extended to the required
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size as the local variables are created by new_localvar().
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When a function is the topmost function being parsed, the
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registers between LexState->dyd.actvar.arr[nactvar]
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and LexState->dyd.actvar.arr[freereg-1]
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are used by the parser for evaluating expressions.
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Note that function parameters are handled in the
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same way as local variables.
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Example of what all this means:
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Let's say we are parsing following chunk of code
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function testfunc()
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-- at this stage 'nactvar' is 0 (no active variables)
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-- 'firstlocal' is set to current top of the variables stack
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-- LexState->dyd.actvar.n (i.e. excluding registers used for expression evaluation)
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-- LexState->dyd.actvar.n = 0 at this stage
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local function tryme()
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-- Since we are inside the local statement and 'tryme' is a local variable,
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-- the LexState->dyd.actvar.n goes to 1. As this is a function definition
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-- the local variable declaration is deemed to end here, so 'nactvar' for testfunc()
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-- is gets set to 1 (making 'tryme' an active variable).
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-- A new FuncState is created for 'tryme' function.
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-- The new tryme() FunState has 'firstlocal' set to value of LexState->dyd.actvar.n, i.e., 1
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local i,j = 5,6
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-- After 'i' is parsed, LexState->dyd.actvar.n = 2, but 'nactvar' = 0 for tryme()
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-- After 'j' is parsed, LexState->dyd.actvar.n = 3, but 'nactvar' = 0 for tryme()
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-- Only after the full statement above is parsed, 'nactvar' for tryme() is set to '2'
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-- This is done by adjustlocalvar().
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return i,j
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end
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-- Here two things happen
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-- Firstly the FuncState for tryme() is popped so that
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-- FuncState for testfunc() is now at top
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-- As part of this popping, leaveblock() calls removevars()
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-- to adjust the LexState->dyd.actvar.n down to 1 where it was
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-- at before parsing the tryme() function body.
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local i, j = tryme()
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-- After 'i' is parsed, LexState->dyd.actvar.n = 2, but 'nactvar' = 1 still
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-- After 'j' is parsed, LexState->dyd.actvar.n = 3, but 'nactvar' = 1 still
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-- At the end of the statement 'nactvar' is set to 3.
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return i+j
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end
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-- As before the leaveblock() calls removevars() which resets
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-- LexState->dyd.actvar.n to 0 (the value before testfunc() was parsed)
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A rough debug trace of the above gives:
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function testfunc()
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-- open_func -> fs->firstlocal set to 0 (ls->dyd->actvar.n), and fs->nactvar reset to 0
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local function tryme()
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-- new_localvar -> registering var tryme fs->f->locvars[0] at ls->dyd->actvar.arr[0]
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-- new_localvar -> ls->dyd->actvar.n set to 1
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-- adjustlocalvars -> set fs->nactvar to 1
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-- open_func -> fs->firstlocal set to 1 (ls->dyd->actvar.n), and fs->nactvar reset to 0
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-- adjustlocalvars -> set fs->nactvar to 0 (no parameters)
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local i,j = 5,6
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-- new_localvar -> registering var i fs->f->locvars[0] at ls->dyd->actvar.arr[1]
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-- new_localvar -> ls->dyd->actvar.n set to 2
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-- new_localvar -> registering var j fs->f->locvars[1] at ls->dyd->actvar.arr[2]
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-- new_localvar -> ls->dyd->actvar.n set to 3
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-- adjustlocalvars -> set fs->nactvar to 2
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return i,j
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-- removevars -> reset fs->nactvar to 0
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end
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local i, j = tryme()
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-- new_localvar -> registering var i fs->f->locvars[1] at ls->dyd->actvar.arr[1]
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-- new_localvar -> ls->dyd->actvar.n set to 2
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-- new_localvar -> registering var j fs->f->locvars[2] at ls->dyd->actvar.arr[2]
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-- new_localvar -> ls->dyd->actvar.n set to 3
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-- adjustlocalvars -> set fs->nactvar to 3
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return i+j
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-- removevars -> reset fs->nactvar to 0
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end
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*/
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typedef struct FuncState {
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Proto *f; /* current function header */
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struct FuncState *prev; /* enclosing function */
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struct LexState *ls; /* lexical state */
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struct BlockCnt *bl; /* chain of current blocks */
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int pc; /* next position to code (equivalent to 'ncode') */
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int lasttarget; /* 'label' of last 'jump label' */
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int jpc; /* list of pending jumps to 'pc' */
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int nk; /* number of elements in 'k' */
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int np; /* number of elements in 'p' */
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int firstlocal; /* index of first local variable (in Dyndata array) -
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this marks the start of the register
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window of the function i.e. register
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zero is here */
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short nlocvars; /* number of elements in 'f->locvars'
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- i.e. number of local variables */
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lu_byte nactvar; /* number of active local variables in
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the function - see note above on how this works */
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lu_byte nups; /* number of upvalues */
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lu_byte freereg; /* first free register - this tracks the top
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of the stack as parsing progresses */
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} FuncState;
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LUAI_FUNC LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
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Dyndata *dyd, const char *name, int firstchar);
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/** RAVI extensions **/
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LUAI_FUNC const char *raviY_typename(ravitype_t tt);
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/* Special printf that recognises following conversions:
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* %e - expdesc *
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* %v - LocVar *
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* %t - Lua types
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* %f - floating decimal
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* %d - int
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* %o - Lua Instruction
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*/
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LUAI_FUNC void raviY_printf(FuncState *fs, const char *format, ...);
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/* Given a local register obtain available type information - if a
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* local variable is associated with the register (i.e. register <= fs->nactvar)
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* in the function type info is available then the type will be returned.
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* Else RAVI_TANY is returned. Note that this function only looks
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* at active local variables - see note on FuncState on what this means.
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*/
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LUAI_FUNC ravitype_t raviY_get_register_typeinfo(FuncState *fs, int reg, TString **);
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#define DEBUG_EXPR(p) \
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if ((ravi_parser_debug & 1) != 0) { \
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p; \
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} else { \
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}
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#define DEBUG_CODEGEN(p) \
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if ((ravi_parser_debug & 2) != 0) { \
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p; \
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} else { \
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}
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#define DEBUG_VARS(p) \
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if ((ravi_parser_debug & 4) != 0) { \
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p; \
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} else { \
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}
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#endif
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