RRG-Proxmark3/client/deps/liblua/ldebug.c

/*
** $Id: ldebug.c $
** Debug Interface
** See Copyright Notice in lua.h
*/

#define ldebug_c
#define LUA_CORE

#include "lprefix.h"


#include <stdarg.h>
#include <stddef.h>
#include <string.h>

#include "lua.h"

#include "lapi.h"
#include "lcode.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lvm.h"



#define LuaClosure(f)		((f) != NULL && (f)->c.tt == LUA_VLCL)


static const char *funcnamefromcall(lua_State *L, CallInfo *ci,
                                    const char **name);


static int currentpc(CallInfo *ci) {
    lua_assert(isLua(ci));
    return pcRel(ci->u.l.savedpc, ci_func(ci)->p);
}


/*
** Get a "base line" to find the line corresponding to an instruction.
** Base lines are regularly placed at MAXIWTHABS intervals, so usually
** an integer division gets the right place. When the source file has
** large sequences of empty/comment lines, it may need extra entries,
** so the original estimate needs a correction.
** If the original estimate is -1, the initial 'if' ensures that the
** 'while' will run at least once.
** The assertion that the estimate is a lower bound for the correct base
** is valid as long as the debug info has been generated with the same
** value for MAXIWTHABS or smaller. (Previous releases use a little
** smaller value.)
*/
static int getbaseline(const Proto *f, int pc, int *basepc) {
    if (f->sizeabslineinfo == 0 || pc < f->abslineinfo[0].pc) {
        *basepc = -1;  /* start from the beginning */
        return f->linedefined;
    } else {
        int i = cast_uint(pc) / MAXIWTHABS - 1;  /* get an estimate */
        /* estimate must be a lower bound of the correct base */
        lua_assert(i < 0 ||
                   (i < f->sizeabslineinfo && f->abslineinfo[i].pc <= pc));
        while (i + 1 < f->sizeabslineinfo && pc >= f->abslineinfo[i + 1].pc)
            i++;  /* low estimate; adjust it */
        *basepc = f->abslineinfo[i].pc;
        return f->abslineinfo[i].line;
    }
}


/*
** Get the line corresponding to instruction 'pc' in function 'f';
** first gets a base line and from there does the increments until
** the desired instruction.
*/
int luaG_getfuncline(const Proto *f, int pc) {
    if (f->lineinfo == NULL)  /* no debug information? */
        return -1;
    else {
        int basepc;
        int baseline = getbaseline(f, pc, &basepc);
        while (basepc++ < pc) {  /* walk until given instruction */
            lua_assert(f->lineinfo[basepc] != ABSLINEINFO);
            baseline += f->lineinfo[basepc];  /* correct line */
        }
        return baseline;
    }
}


static int getcurrentline(CallInfo *ci) {
    return luaG_getfuncline(ci_func(ci)->p, currentpc(ci));
}


/*
** Set 'trap' for all active Lua frames.
** This function can be called during a signal, under "reasonable"
** assumptions. A new 'ci' is completely linked in the list before it
** becomes part of the "active" list, and we assume that pointers are
** atomic; see comment in next function.
** (A compiler doing interprocedural optimizations could, theoretically,
** reorder memory writes in such a way that the list could be
** temporarily broken while inserting a new element. We simply assume it
** has no good reasons to do that.)
*/
static void settraps(CallInfo *ci) {
    for (; ci != NULL; ci = ci->previous)
        if (isLua(ci))
            ci->u.l.trap = 1;
}


/*
** This function can be called during a signal, under "reasonable"
** assumptions.
** Fields 'basehookcount' and 'hookcount' (set by 'resethookcount')
** are for debug only, and it is no problem if they get arbitrary
** values (causes at most one wrong hook call). 'hookmask' is an atomic
** value. We assume that pointers are atomic too (e.g., gcc ensures that
** for all platforms where it runs). Moreover, 'hook' is always checked
** before being called (see 'luaD_hook').
*/
LUA_API void lua_sethook(lua_State *L, lua_Hook func, int mask, int count) {
    if (func == NULL || mask == 0) {  /* turn off hooks? */
        mask = 0;
        func = NULL;
    }
    L->hook = func;
    L->basehookcount = count;
    resethookcount(L);
    L->hookmask = cast_byte(mask);
    if (mask)
        settraps(L->ci);  /* to trace inside 'luaV_execute' */
}


LUA_API lua_Hook lua_gethook(lua_State *L) {
    return L->hook;
}


LUA_API int lua_gethookmask(lua_State *L) {
    return L->hookmask;
}


LUA_API int lua_gethookcount(lua_State *L) {
    return L->basehookcount;
}


LUA_API int lua_getstack(lua_State *L, int level, lua_Debug *ar) {
    int status;
    CallInfo *ci;
    if (level < 0) return 0;  /* invalid (negative) level */
    lua_lock(L);
    for (ci = L->ci; level > 0 && ci != &L->base_ci; ci = ci->previous)
        level--;
    if (level == 0 && ci != &L->base_ci) {  /* level found? */
        status = 1;
        ar->i_ci = ci;
    } else status = 0; /* no such level */
    lua_unlock(L);
    return status;
}


static const char *upvalname(const Proto *p, int uv) {
    TString *s = check_exp(uv < p->sizeupvalues, p->upvalues[uv].name);
    if (s == NULL) return "?";
    else return getstr(s);
}


static const char *findvararg(CallInfo *ci, int n, StkId *pos) {
    if (clLvalue(s2v(ci->func.p))->p->is_vararg) {
        int nextra = ci->u.l.nextraargs;
        if (n >= -nextra) {  /* 'n' is negative */
            *pos = ci->func.p - nextra - (n + 1);
            return "(vararg)";  /* generic name for any vararg */
        }
    }
    return NULL;  /* no such vararg */
}


const char *luaG_findlocal(lua_State *L, CallInfo *ci, int n, StkId *pos) {
    StkId base = ci->func.p + 1;
    const char *name = NULL;
    if (isLua(ci)) {
        if (n < 0)  /* access to vararg values? */
            return findvararg(ci, n, pos);
        else
            name = luaF_getlocalname(ci_func(ci)->p, n, currentpc(ci));
    }
    if (name == NULL) {  /* no 'standard' name? */
        StkId limit = (ci == L->ci) ? L->top.p : ci->next->func.p;
        if (limit - base >= n && n > 0) {  /* is 'n' inside 'ci' stack? */
            /* generic name for any valid slot */
            name = isLua(ci) ? "(temporary)" : "(C temporary)";
        } else
            return NULL;  /* no name */
    }
    if (pos)
        *pos = base + (n - 1);
    return name;
}


LUA_API const char *lua_getlocal(lua_State *L, const lua_Debug *ar, int n) {
    const char *name;
    lua_lock(L);
    if (ar == NULL) {  /* information about non-active function? */
        if (!isLfunction(s2v(L->top.p - 1)))  /* not a Lua function? */
            name = NULL;
        else  /* consider live variables at function start (parameters) */
            name = luaF_getlocalname(clLvalue(s2v(L->top.p - 1))->p, n, 0);
    } else { /* active function; get information through 'ar' */
        StkId pos = NULL;  /* to avoid warnings */
        name = luaG_findlocal(L, ar->i_ci, n, &pos);
        if (name) {
            setobjs2s(L, L->top.p, pos);
            api_incr_top(L);
        }
    }
    lua_unlock(L);
    return name;
}


LUA_API const char *lua_setlocal(lua_State *L, const lua_Debug *ar, int n) {
    StkId pos = NULL;  /* to avoid warnings */
    const char *name;
    lua_lock(L);
    name = luaG_findlocal(L, ar->i_ci, n, &pos);
    if (name) {
        setobjs2s(L, pos, L->top.p - 1);
        L->top.p--;  /* pop value */
    }
    lua_unlock(L);
    return name;
}


static void funcinfo(lua_Debug *ar, Closure *cl) {
    if (!LuaClosure(cl)) {
        ar->source = "=[C]";
        ar->srclen = LL("=[C]");
        ar->linedefined = -1;
        ar->lastlinedefined = -1;
        ar->what = "C";
    } else {
        const Proto *p = cl->l.p;
        if (p->source) {
            ar->source = getstr(p->source);
            ar->srclen = tsslen(p->source);
        } else {
            ar->source = "=?";
            ar->srclen = LL("=?");
        }
        ar->linedefined = p->linedefined;
        ar->lastlinedefined = p->lastlinedefined;
        ar->what = (ar->linedefined == 0) ? "main" : "Lua";
    }
    luaO_chunkid(ar->short_src, ar->source, ar->srclen);
}


static int nextline(const Proto *p, int currentline, int pc) {
    if (p->lineinfo[pc] != ABSLINEINFO)
        return currentline + p->lineinfo[pc];
    else
        return luaG_getfuncline(p, pc);
}


static void collectvalidlines(lua_State *L, Closure *f) {
    if (!LuaClosure(f)) {
        setnilvalue(s2v(L->top.p));
        api_incr_top(L);
    } else {
        const Proto *p = f->l.p;
        int currentline = p->linedefined;
        Table *t = luaH_new(L);  /* new table to store active lines */
        sethvalue2s(L, L->top.p, t);  /* push it on stack */
        api_incr_top(L);
        if (p->lineinfo != NULL) {  /* proto with debug information? */
            int i;
            TValue v;
            setbtvalue(&v);  /* boolean 'true' to be the value of all indices */
            if (!p->is_vararg)  /* regular function? */
                i = 0;  /* consider all instructions */
            else {  /* vararg function */
                lua_assert(GET_OPCODE(p->code[0]) == OP_VARARGPREP);
                currentline = nextline(p, currentline, 0);
                i = 1;  /* skip first instruction (OP_VARARGPREP) */
            }
            for (; i < p->sizelineinfo; i++) {  /* for each instruction */
                currentline = nextline(p, currentline, i);  /* get its line */
                luaH_setint(L, t, currentline, &v);  /* table[line] = true */
            }
        }
    }
}


static const char *getfuncname(lua_State *L, CallInfo *ci, const char **name) {
    /* calling function is a known function? */
    if (ci != NULL && !(ci->callstatus & CIST_TAIL))
        return funcnamefromcall(L, ci->previous, name);
    else return NULL;  /* no way to find a name */
}


static int auxgetinfo(lua_State *L, const char *what, lua_Debug *ar,
                      Closure *f, CallInfo *ci) {
    int status = 1;
    for (; *what; what++) {
        switch (*what) {
            case 'S': {
                funcinfo(ar, f);
                break;
            }
            case 'l': {
                ar->currentline = (ci && isLua(ci)) ? getcurrentline(ci) : -1;
                break;
            }
            case 'u': {
                ar->nups = (f == NULL) ? 0 : f->c.nupvalues;
                if (!LuaClosure(f)) {
                    ar->isvararg = 1;
                    ar->nparams = 0;
                } else {
                    ar->isvararg = f->l.p->is_vararg;
                    ar->nparams = f->l.p->numparams;
                }
                break;
            }
            case 't': {
                ar->istailcall = (ci) ? ci->callstatus & CIST_TAIL : 0;
                break;
            }
            case 'n': {
                ar->namewhat = getfuncname(L, ci, &ar->name);
                if (ar->namewhat == NULL) {
                    ar->namewhat = "";  /* not found */
                    ar->name = NULL;
                }
                break;
            }
            case 'r': {
                if (ci == NULL || !(ci->callstatus & CIST_TRAN))
                    ar->ftransfer = ar->ntransfer = 0;
                else {
                    ar->ftransfer = ci->u2.transferinfo.ftransfer;
                    ar->ntransfer = ci->u2.transferinfo.ntransfer;
                }
                break;
            }
            case 'L':
            case 'f':  /* handled by lua_getinfo */
                break;
            default:
                status = 0;  /* invalid option */
        }
    }
    return status;
}


LUA_API int lua_getinfo(lua_State *L, const char *what, lua_Debug *ar) {
    int status;
    Closure *cl;
    CallInfo *ci;
    TValue *func;
    lua_lock(L);
    if (*what == '>') {
        ci = NULL;
        func = s2v(L->top.p - 1);
        api_check(L, ttisfunction(func), "function expected");
        what++;  /* skip the '>' */
        L->top.p--;  /* pop function */
    } else {
        ci = ar->i_ci;
        func = s2v(ci->func.p);
        lua_assert(ttisfunction(func));
    }
    cl = ttisclosure(func) ? clvalue(func) : NULL;
    status = auxgetinfo(L, what, ar, cl, ci);
    if (strchr(what, 'f')) {
        setobj2s(L, L->top.p, func);
        api_incr_top(L);
    }
    if (strchr(what, 'L'))
        collectvalidlines(L, cl);
    lua_unlock(L);
    return status;
}


/*
** {======================================================
** Symbolic Execution
** =======================================================
*/


static int filterpc(int pc, int jmptarget) {
    if (pc < jmptarget)  /* is code conditional (inside a jump)? */
        return -1;  /* cannot know who sets that register */
    else return pc;  /* current position sets that register */
}


/*
** Try to find last instruction before 'lastpc' that modified register 'reg'.
*/
static int findsetreg(const Proto *p, int lastpc, int reg) {
    int pc;
    int setreg = -1;  /* keep last instruction that changed 'reg' */
    int jmptarget = 0;  /* any code before this address is conditional */
    if (testMMMode(GET_OPCODE(p->code[lastpc])))
        lastpc--;  /* previous instruction was not actually executed */
    for (pc = 0; pc < lastpc; pc++) {
        Instruction i = p->code[pc];
        OpCode op = GET_OPCODE(i);
        int a = GETARG_A(i);
        int change;  /* true if current instruction changed 'reg' */
        switch (op) {
            case OP_LOADNIL: {  /* set registers from 'a' to 'a+b' */
                int b = GETARG_B(i);
                change = (a <= reg && reg <= a + b);
                break;
            }
            case OP_TFORCALL: {  /* affect all regs above its base */
                change = (reg >= a + 2);
                break;
            }
            case OP_CALL:
            case OP_TAILCALL: {  /* affect all registers above base */
                change = (reg >= a);
                break;
            }
            case OP_JMP: {  /* doesn't change registers, but changes 'jmptarget' */
                int b = GETARG_sJ(i);
                int dest = pc + 1 + b;
                /* jump does not skip 'lastpc' and is larger than current one? */
                if (dest <= lastpc && dest > jmptarget)
                    jmptarget = dest;  /* update 'jmptarget' */
                change = 0;
                break;
            }
            default:  /* any instruction that sets A */
                change = (testAMode(op) && reg == a);
                break;
        }
        if (change)
            setreg = filterpc(pc, jmptarget);
    }
    return setreg;
}


/*
** Find a "name" for the constant 'c'.
*/
static const char *kname(const Proto *p, int index, const char **name) {
    TValue *kvalue = &p->k[index];
    if (ttisstring(kvalue)) {
        *name = getstr(tsvalue(kvalue));
        return "constant";
    } else {
        *name = "?";
        return NULL;
    }
}


static const char *basicgetobjname(const Proto *p, int *ppc, int reg,
                                   const char **name) {
    int pc = *ppc;
    *name = luaF_getlocalname(p, reg + 1, pc);
    if (*name)  /* is a local? */
        return "local";
    /* else try symbolic execution */
    *ppc = pc = findsetreg(p, pc, reg);
    if (pc != -1) {  /* could find instruction? */
        Instruction i = p->code[pc];
        OpCode op = GET_OPCODE(i);
        switch (op) {
            case OP_MOVE: {
                int b = GETARG_B(i);  /* move from 'b' to 'a' */
                if (b < GETARG_A(i))
                    return basicgetobjname(p, ppc, b, name);  /* get name for 'b' */
                break;
            }
            case OP_GETUPVAL: {
                *name = upvalname(p, GETARG_B(i));
                return "upvalue";
            }
            case OP_LOADK:
                return kname(p, GETARG_Bx(i), name);
            case OP_LOADKX:
                return kname(p, GETARG_Ax(p->code[pc + 1]), name);
            default:
                break;
        }
    }
    return NULL;  /* could not find reasonable name */
}


/*
** Find a "name" for the register 'c'.
*/
static void rname(const Proto *p, int pc, int c, const char **name) {
    const char *what = basicgetobjname(p, &pc, c, name); /* search for 'c' */
    if (!(what && *what == 'c'))  /* did not find a constant name? */
        *name = "?";
}


/*
** Find a "name" for a 'C' value in an RK instruction.
*/
static void rkname(const Proto *p, int pc, Instruction i, const char **name) {
    int c = GETARG_C(i);  /* key index */
    if (GETARG_k(i))  /* is 'c' a constant? */
        kname(p, c, name);
    else  /* 'c' is a register */
        rname(p, pc, c, name);
}


/*
** Check whether table being indexed by instruction 'i' is the
** environment '_ENV'
*/
static const char *isEnv(const Proto *p, int pc, Instruction i, int isup) {
    int t = GETARG_B(i);  /* table index */
    const char *name;  /* name of indexed variable */
    if (isup)  /* is 't' an upvalue? */
        name = upvalname(p, t);
    else  /* 't' is a register */
        basicgetobjname(p, &pc, t, &name);
    return (name && strcmp(name, LUA_ENV) == 0) ? "global" : "field";
}


/*
** Extend 'basicgetobjname' to handle table accesses
*/
static const char *getobjname(const Proto *p, int lastpc, int reg,
                              const char **name) {
    const char *kind = basicgetobjname(p, &lastpc, reg, name);
    if (kind != NULL)
        return kind;
    else if (lastpc != -1) {  /* could find instruction? */
        Instruction i = p->code[lastpc];
        OpCode op = GET_OPCODE(i);
        switch (op) {
            case OP_GETTABUP: {
                int k = GETARG_C(i);  /* key index */
                kname(p, k, name);
                return isEnv(p, lastpc, i, 1);
            }
            case OP_GETTABLE: {
                int k = GETARG_C(i);  /* key index */
                rname(p, lastpc, k, name);
                return isEnv(p, lastpc, i, 0);
            }
            case OP_GETI: {
                *name = "integer index";
                return "field";
            }
            case OP_GETFIELD: {
                int k = GETARG_C(i);  /* key index */
                kname(p, k, name);
                return isEnv(p, lastpc, i, 0);
            }
            case OP_SELF: {
                rkname(p, lastpc, i, name);
                return "method";
            }
            default:
                break;  /* go through to return NULL */
        }
    }
    return NULL;  /* could not find reasonable name */
}


/*
** Try to find a name for a function based on the code that called it.
** (Only works when function was called by a Lua function.)
** Returns what the name is (e.g., "for iterator", "method",
** "metamethod") and sets '*name' to point to the name.
*/
static const char *funcnamefromcode(lua_State *L, const Proto *p,
                                    int pc, const char **name) {
    TMS tm = (TMS)0;  /* (initial value avoids warnings) */
    Instruction i = p->code[pc];  /* calling instruction */
    switch (GET_OPCODE(i)) {
        case OP_CALL:
        case OP_TAILCALL:
            return getobjname(p, pc, GETARG_A(i), name);  /* get function name */
        case OP_TFORCALL: {  /* for iterator */
            *name = "for iterator";
            return "for iterator";
        }
        /* other instructions can do calls through metamethods */
        case OP_SELF:
        case OP_GETTABUP:
        case OP_GETTABLE:
        case OP_GETI:
        case OP_GETFIELD:
            tm = TM_INDEX;
            break;
        case OP_SETTABUP:
        case OP_SETTABLE:
        case OP_SETI:
        case OP_SETFIELD:
            tm = TM_NEWINDEX;
            break;
        case OP_MMBIN:
        case OP_MMBINI:
        case OP_MMBINK: {
            tm = cast(TMS, GETARG_C(i));
            break;
        }
        case OP_UNM:
            tm = TM_UNM;
            break;
        case OP_BNOT:
            tm = TM_BNOT;
            break;
        case OP_LEN:
            tm = TM_LEN;
            break;
        case OP_CONCAT:
            tm = TM_CONCAT;
            break;
        case OP_EQ:
            tm = TM_EQ;
            break;
        /* no cases for OP_EQI and OP_EQK, as they don't call metamethods */
        case OP_LT:
        case OP_LTI:
        case OP_GTI:
            tm = TM_LT;
            break;
        case OP_LE:
        case OP_LEI:
        case OP_GEI:
            tm = TM_LE;
            break;
        case OP_CLOSE:
        case OP_RETURN:
            tm = TM_CLOSE;
            break;
        default:
            return NULL;  /* cannot find a reasonable name */
    }
    *name = getshrstr(G(L)->tmname[tm]) + 2;
    return "metamethod";
}


/*
** Try to find a name for a function based on how it was called.
*/
static const char *funcnamefromcall(lua_State *L, CallInfo *ci,
                                    const char **name) {
    if (ci->callstatus & CIST_HOOKED) {  /* was it called inside a hook? */
        *name = "?";
        return "hook";
    } else if (ci->callstatus & CIST_FIN) { /* was it called as a finalizer? */
        *name = "__gc";
        return "metamethod";  /* report it as such */
    } else if (isLua(ci))
        return funcnamefromcode(L, ci_func(ci)->p, currentpc(ci), name);
    else
        return NULL;
}

/* }====================================================== */



/*
** Check whether pointer 'o' points to some value in the stack frame of
** the current function and, if so, returns its index.  Because 'o' may
** not point to a value in this stack, we cannot compare it with the
** region boundaries (undefined behavior in ISO C).
*/
static int instack(CallInfo *ci, const TValue *o) {
    int pos;
    StkId base = ci->func.p + 1;
    for (pos = 0; base + pos < ci->top.p; pos++) {
        if (o == s2v(base + pos))
            return pos;
    }
    return -1;  /* not found */
}


/*
** Checks whether value 'o' came from an upvalue. (That can only happen
** with instructions OP_GETTABUP/OP_SETTABUP, which operate directly on
** upvalues.)
*/
static const char *getupvalname(CallInfo *ci, const TValue *o,
                                const char **name) {
    LClosure *c = ci_func(ci);
    int i;
    for (i = 0; i < c->nupvalues; i++) {
        if (c->upvals[i]->v.p == o) {
            *name = upvalname(c->p, i);
            return "upvalue";
        }
    }
    return NULL;
}


static const char *formatvarinfo(lua_State *L, const char *kind,
                                 const char *name) {
    if (kind == NULL)
        return "";  /* no information */
    else
        return luaO_pushfstring(L, " (%s '%s')", kind, name);
}

/*
** Build a string with a "description" for the value 'o', such as
** "variable 'x'" or "upvalue 'y'".
*/
static const char *varinfo(lua_State *L, const TValue *o) {
    CallInfo *ci = L->ci;
    const char *name = NULL;  /* to avoid warnings */
    const char *kind = NULL;
    if (isLua(ci)) {
        kind = getupvalname(ci, o, &name);  /* check whether 'o' is an upvalue */
        if (!kind) {  /* not an upvalue? */
            int reg = instack(ci, o);  /* try a register */
            if (reg >= 0)  /* is 'o' a register? */
                kind = getobjname(ci_func(ci)->p, currentpc(ci), reg, &name);
        }
    }
    return formatvarinfo(L, kind, name);
}


/*
** Raise a type error
*/
static l_noret typeerror(lua_State *L, const TValue *o, const char *op,
                         const char *extra) {
    const char *t = luaT_objtypename(L, o);
    luaG_runerror(L, "attempt to %s a %s value%s", op, t, extra);
}


/*
** Raise a type error with "standard" information about the faulty
** object 'o' (using 'varinfo').
*/
l_noret luaG_typeerror(lua_State *L, const TValue *o, const char *op) {
    typeerror(L, o, op, varinfo(L, o));
}


/*
** Raise an error for calling a non-callable object. Try to find a name
** for the object based on how it was called ('funcnamefromcall'); if it
** cannot get a name there, try 'varinfo'.
*/
l_noret luaG_callerror(lua_State *L, const TValue *o) {
    CallInfo *ci = L->ci;
    const char *name = NULL;  /* to avoid warnings */
    const char *kind = funcnamefromcall(L, ci, &name);
    const char *extra = kind ? formatvarinfo(L, kind, name) : varinfo(L, o);
    typeerror(L, o, "call", extra);
}


l_noret luaG_forerror(lua_State *L, const TValue *o, const char *what) {
    luaG_runerror(L, "bad 'for' %s (number expected, got %s)",
                  what, luaT_objtypename(L, o));
}


l_noret luaG_concaterror(lua_State *L, const TValue *p1, const TValue *p2) {
    if (ttisstring(p1) || cvt2str(p1)) p1 = p2;
    luaG_typeerror(L, p1, "concatenate");
}


l_noret luaG_opinterror(lua_State *L, const TValue *p1,
                        const TValue *p2, const char *msg) {
    if (!ttisnumber(p1))  /* first operand is wrong? */
        p2 = p1;  /* now second is wrong */
    luaG_typeerror(L, p2, msg);
}


/*
** Error when both values are convertible to numbers, but not to integers
*/
l_noret luaG_tointerror(lua_State *L, const TValue *p1, const TValue *p2) {
    lua_Integer temp;
    if (!luaV_tointegerns(p1, &temp, LUA_FLOORN2I))
        p2 = p1;
    luaG_runerror(L, "number%s has no integer representation", varinfo(L, p2));
}


l_noret luaG_ordererror(lua_State *L, const TValue *p1, const TValue *p2) {
    const char *t1 = luaT_objtypename(L, p1);
    const char *t2 = luaT_objtypename(L, p2);
    if (strcmp(t1, t2) == 0)
        luaG_runerror(L, "attempt to compare two %s values", t1);
    else
        luaG_runerror(L, "attempt to compare %s with %s", t1, t2);
}


/* add src:line information to 'msg' */
const char *luaG_addinfo(lua_State *L, const char *msg, TString *src,
                         int line) {
    char buff[LUA_IDSIZE];
    if (src)
        luaO_chunkid(buff, getstr(src), tsslen(src));
    else {  /* no source available; use "?" instead */
        buff[0] = '?';
        buff[1] = '\0';
    }
    return luaO_pushfstring(L, "%s:%d: %s", buff, line, msg);
}


l_noret luaG_errormsg(lua_State *L) {
    if (L->errfunc != 0) {  /* is there an error handling function? */
        StkId errfunc = restorestack(L, L->errfunc);
        lua_assert(ttisfunction(s2v(errfunc)));
        setobjs2s(L, L->top.p, L->top.p - 1);  /* move argument */
        setobjs2s(L, L->top.p - 1, errfunc);  /* push function */
        L->top.p++;  /* assume EXTRA_STACK */
        luaD_callnoyield(L, L->top.p - 2, 1);  /* call it */
    }
    luaD_throw(L, LUA_ERRRUN);
}


l_noret luaG_runerror(lua_State *L, const char *fmt, ...) {
    CallInfo *ci = L->ci;
    const char *msg;
    va_list argp;
    luaC_checkGC(L);  /* error message uses memory */
    va_start(argp, fmt);
    msg = luaO_pushvfstring(L, fmt, argp);  /* format message */
    va_end(argp);
    if (isLua(ci)) {  /* if Lua function, add source:line information */
        luaG_addinfo(L, msg, ci_func(ci)->p->source, getcurrentline(ci));
        setobjs2s(L, L->top.p - 2, L->top.p - 1);  /* remove 'msg' */
        L->top.p--;
    }
    luaG_errormsg(L);
}


/*
** Check whether new instruction 'newpc' is in a different line from
** previous instruction 'oldpc'. More often than not, 'newpc' is only
** one or a few instructions after 'oldpc' (it must be after, see
** caller), so try to avoid calling 'luaG_getfuncline'. If they are
** too far apart, there is a good chance of a ABSLINEINFO in the way,
** so it goes directly to 'luaG_getfuncline'.
*/
static int changedline(const Proto *p, int oldpc, int newpc) {
    if (p->lineinfo == NULL)  /* no debug information? */
        return 0;
    if (newpc - oldpc < MAXIWTHABS / 2) {  /* not too far apart? */
        int delta = 0;  /* line difference */
        int pc = oldpc;
        for (;;) {
            int lineinfo = p->lineinfo[++pc];
            if (lineinfo == ABSLINEINFO)
                break;  /* cannot compute delta; fall through */
            delta += lineinfo;
            if (pc == newpc)
                return (delta != 0);  /* delta computed successfully */
        }
    }
    /* either instructions are too far apart or there is an absolute line
       info in the way; compute line difference explicitly */
    return (luaG_getfuncline(p, oldpc) != luaG_getfuncline(p, newpc));
}


/*
** Traces Lua calls. If code is running the first instruction of a function,
** and function is not vararg, and it is not coming from an yield,
** calls 'luaD_hookcall'. (Vararg functions will call 'luaD_hookcall'
** after adjusting its variable arguments; otherwise, they could call
** a line/count hook before the call hook. Functions coming from
** an yield already called 'luaD_hookcall' before yielding.)
*/
int luaG_tracecall(lua_State *L) {
    CallInfo *ci = L->ci;
    Proto *p = ci_func(ci)->p;
    ci->u.l.trap = 1;  /* ensure hooks will be checked */
    if (ci->u.l.savedpc == p->code) {  /* first instruction (not resuming)? */
        if (p->is_vararg)
            return 0;  /* hooks will start at VARARGPREP instruction */
        else if (!(ci->callstatus & CIST_HOOKYIELD))  /* not yieded? */
            luaD_hookcall(L, ci);  /* check 'call' hook */
    }
    return 1;  /* keep 'trap' on */
}


/*
** Traces the execution of a Lua function. Called before the execution
** of each opcode, when debug is on. 'L->oldpc' stores the last
** instruction traced, to detect line changes. When entering a new
** function, 'npci' will be zero and will test as a new line whatever
** the value of 'oldpc'.  Some exceptional conditions may return to
** a function without setting 'oldpc'. In that case, 'oldpc' may be
** invalid; if so, use zero as a valid value. (A wrong but valid 'oldpc'
** at most causes an extra call to a line hook.)
** This function is not "Protected" when called, so it should correct
** 'L->top.p' before calling anything that can run the GC.
*/
int luaG_traceexec(lua_State *L, const Instruction *pc) {
    CallInfo *ci = L->ci;
    lu_byte mask = L->hookmask;
    const Proto *p = ci_func(ci)->p;
    int counthook;
    if (!(mask & (LUA_MASKLINE | LUA_MASKCOUNT))) {  /* no hooks? */
        ci->u.l.trap = 0;  /* don't need to stop again */
        return 0;  /* turn off 'trap' */
    }
    pc++;  /* reference is always next instruction */
    ci->u.l.savedpc = pc;  /* save 'pc' */
    counthook = (mask & LUA_MASKCOUNT) && (--L->hookcount == 0);
    if (counthook)
        resethookcount(L);  /* reset count */
    else if (!(mask & LUA_MASKLINE))
        return 1;  /* no line hook and count != 0; nothing to be done now */
    if (ci->callstatus & CIST_HOOKYIELD) {  /* hook yielded last time? */
        ci->callstatus &= ~CIST_HOOKYIELD;  /* erase mark */
        return 1;  /* do not call hook again (VM yielded, so it did not move) */
    }
    if (!isIT(*(ci->u.l.savedpc - 1)))  /* top not being used? */
        L->top.p = ci->top.p;  /* correct top */
    if (counthook)
        luaD_hook(L, LUA_HOOKCOUNT, -1, 0, 0);  /* call count hook */
    if (mask & LUA_MASKLINE) {
        /* 'L->oldpc' may be invalid; use zero in this case */
        int oldpc = (L->oldpc < p->sizecode) ? L->oldpc : 0;
        int npci = pcRel(pc, p);
        if (npci <= oldpc ||  /* call hook when jump back (loop), */
                changedline(p, oldpc, npci)) {  /* or when enter new line */
            int newline = luaG_getfuncline(p, npci);
            luaD_hook(L, LUA_HOOKLINE, newline, 0, 0);  /* call line hook */
        }
        L->oldpc = npci;  /* 'pc' of last call to line hook */
    }
    if (L->status == LUA_YIELD) {  /* did hook yield? */
        if (counthook)
            L->hookcount = 1;  /* undo decrement to zero */
        ci->callstatus |= CIST_HOOKYIELD;  /* mark that it yielded */
        luaD_throw(L, LUA_YIELD);
    }
    return 1;  /* keep 'trap' on */
}