/*    cop.h
 *
 *    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
 *    2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, by Larry Wall and others
 *
 *    You may distribute under the terms of either the GNU General Public
 *    License or the Artistic License, as specified in the README file.
 *
 * Control ops (cops) are one of the three ops OP_NEXTSTATE, OP_DBSTATE,
 * and OP_SETSTATE that (loosely speaking) are separate statements.
 * They hold information important for lexical state and error reporting.
 * At run time, PL_curcop is set to point to the most recently executed cop,
 * and thus can be used to determine our current state.
 */

/* A jmpenv packages the state required to perform a proper non-local jump.
 * Note that there is a start_env initialized when perl starts, and top_env
 * points to this initially, so top_env should always be non-null.
 *
 * Existence of a non-null top_env->je_prev implies it is valid to call
 * longjmp() at that runlevel (we make sure start_env.je_prev is always
 * null to ensure this).
 *
 * je_mustcatch, when set at any runlevel to TRUE, means eval ops must
 * establish a local jmpenv to handle exception traps.  Care must be taken
 * to restore the previous value of je_mustcatch before exiting the
 * stack frame iff JMPENV_PUSH was not called in that stack frame.
 * GSAR 97-03-27
 */

struct jmpenv {
    struct jmpenv *	je_prev;
    Sigjmp_buf		je_buf;		/* only for use if !je_throw */
    int			je_ret;		/* last exception thrown */
    bool		je_mustcatch;	/* need to call longjmp()? */
};

typedef struct jmpenv JMPENV;

#ifdef OP_IN_REGISTER
#define OP_REG_TO_MEM	PL_opsave = op
#define OP_MEM_TO_REG	op = PL_opsave
#else
#define OP_REG_TO_MEM	NOOP
#define OP_MEM_TO_REG	NOOP
#endif

/*
 * How to build the first jmpenv.
 *
 * top_env needs to be non-zero. It points to an area
 * in which longjmp() stuff is stored, as C callstack
 * info there at least is thread specific this has to
 * be per-thread. Otherwise a 'die' in a thread gives
 * that thread the C stack of last thread to do an eval {}!
 */

#define JMPENV_BOOTSTRAP \
    STMT_START {				\
	Zero(&PL_start_env, 1, JMPENV);		\
	PL_start_env.je_ret = -1;		\
	PL_start_env.je_mustcatch = TRUE;	\
	PL_top_env = &PL_start_env;		\
    } STMT_END

/*
 *   PERL_FLEXIBLE_EXCEPTIONS
 * 
 * All the flexible exceptions code has been removed.
 * See the following threads for details:
 *
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2004-07/msg00378.html
 * 
 * Joshua's original patches (which weren't applied) and discussion:
 * 
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg01396.html
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg01489.html
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg01491.html
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg01608.html
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg02144.html
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1998-02/msg02998.html
 * 
 * Chip's reworked patch and discussion:
 * 
 *   http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/1999-03/msg00520.html
 * 
 * The flaw in these patches (which went unnoticed at the time) was
 * that they moved some code that could potentially die() out of the
 * region protected by the setjmp()s.  This caused exceptions within
 * END blocks and such to not be handled by the correct setjmp().
 * 
 * The original patches that introduces flexible exceptions were:
 *
 *   http://public.activestate.com/cgi-bin/perlbrowse?patch=3386
 *   http://public.activestate.com/cgi-bin/perlbrowse?patch=5162
 */

#define dJMPENV		JMPENV cur_env

#define JMPENV_PUSH(v) \
    STMT_START {							\
	DEBUG_l(Perl_deb(aTHX_ "Setting up jumplevel %p, was %p\n",	\
			 (void*)&cur_env, (void*)PL_top_env));			\
	cur_env.je_prev = PL_top_env;					\
	OP_REG_TO_MEM;							\
	cur_env.je_ret = PerlProc_setjmp(cur_env.je_buf, SCOPE_SAVES_SIGNAL_MASK);		\
	OP_MEM_TO_REG;							\
	PL_top_env = &cur_env;						\
	cur_env.je_mustcatch = FALSE;					\
	(v) = cur_env.je_ret;						\
    } STMT_END

#define JMPENV_POP \
    STMT_START {							\
	DEBUG_l(Perl_deb(aTHX_ "popping jumplevel was %p, now %p\n",	\
			 (void*)PL_top_env, (void*)cur_env.je_prev));			\
	PL_top_env = cur_env.je_prev;					\
    } STMT_END

#define JMPENV_JUMP(v) \
    STMT_START {						\
	OP_REG_TO_MEM;						\
	if (PL_top_env->je_prev)				\
	    PerlProc_longjmp(PL_top_env->je_buf, (v));		\
	if ((v) == 2)						\
	    PerlProc_exit(STATUS_EXIT);		                \
	PerlIO_printf(PerlIO_stderr(), "panic: top_env\n");	\
	PerlProc_exit(1);					\
    } STMT_END

#define CATCH_GET		(PL_top_env->je_mustcatch)
#define CATCH_SET(v)		(PL_top_env->je_mustcatch = (v))



struct cop {
    BASEOP
    /* On LP64 putting this here takes advantage of the fact that BASEOP isn't
       an exact multiple of 8 bytes to save structure padding.  */
    line_t      cop_line;       /* line # of this command */
    char *	cop_label;	/* label for this construct */
#ifdef USE_ITHREADS
    char *	cop_stashpv;	/* package line was compiled in */
    char *	cop_file;	/* file name the following line # is from */
#else
    HV *	cop_stash;	/* package line was compiled in */
    GV *	cop_filegv;	/* file the following line # is from */
#endif
    U32		cop_hints;	/* hints bits from pragmata */
    U32		cop_seq;	/* parse sequence number */
    /* Beware. mg.c and warnings.pl assume the type of this is STRLEN *:  */
    STRLEN *	cop_warnings;	/* lexical warnings bitmask */
    /* compile time state of %^H.  See the comment in op.c for how this is
       used to recreate a hash to return from caller.  */
    struct refcounted_he * cop_hints_hash;
};

#ifdef USE_ITHREADS
#  define CopFILE(c)		((c)->cop_file)
#  define CopFILEGV(c)		(CopFILE(c) \
				 ? gv_fetchfile(CopFILE(c)) : NULL)
				 
#  ifdef NETWARE
#    define CopFILE_set(c,pv)	((c)->cop_file = savepv(pv))
#    define CopFILE_setn(c,pv,l)  ((c)->cop_file = savepv((pv),(l)))
#  else
#    define CopFILE_set(c,pv)	((c)->cop_file = savesharedpv(pv))
#    define CopFILE_setn(c,pv,l)  ((c)->cop_file = savesharedpvn((pv),(l)))
#  endif

#  define CopFILESV(c)		(CopFILE(c) \
				 ? GvSV(gv_fetchfile(CopFILE(c))) : NULL)
#  define CopFILEAV(c)		(CopFILE(c) \
				 ? GvAV(gv_fetchfile(CopFILE(c))) : NULL)
#  ifdef DEBUGGING
#    define CopFILEAVx(c)	(assert(CopFILE(c)), \
				   GvAV(gv_fetchfile(CopFILE(c))))
#  else
#    define CopFILEAVx(c)	(GvAV(gv_fetchfile(CopFILE(c))))
#  endif
#  define CopSTASHPV(c)		((c)->cop_stashpv)

#  ifdef NETWARE
#    define CopSTASHPV_set(c,pv)	((c)->cop_stashpv = ((pv) ? savepv(pv) : NULL))
#  else
#    define CopSTASHPV_set(c,pv)	((c)->cop_stashpv = savesharedpv(pv))
#  endif

#  define CopSTASH(c)		(CopSTASHPV(c) \
				 ? gv_stashpv(CopSTASHPV(c),GV_ADD) : NULL)
#  define CopSTASH_set(c,hv)	CopSTASHPV_set(c, (hv) ? HvNAME_get(hv) : NULL)
#  define CopSTASH_eq(c,hv)	((hv) && stashpv_hvname_match(c,hv))
#  define CopLABEL(c)		((c)->cop_label)
#  define CopLABEL_set(c,pv)	(CopLABEL(c) = (pv))
#  ifdef NETWARE
#    define CopSTASH_free(c) SAVECOPSTASH_FREE(c)
#    define CopFILE_free(c) SAVECOPFILE_FREE(c)
#    define CopLABEL_free(c) SAVECOPLABEL_FREE(c)
#    define CopLABEL_alloc(pv)	((pv)?savepv(pv):NULL)
#  else
#    define CopSTASH_free(c)	PerlMemShared_free(CopSTASHPV(c))
#    define CopFILE_free(c)	(PerlMemShared_free(CopFILE(c)),(CopFILE(c) = NULL))
#    define CopLABEL_free(c)	(PerlMemShared_free(CopLABEL(c)),(CopLABEL(c) = NULL))
#    define CopLABEL_alloc(pv)	((pv)?savesharedpv(pv):NULL)
#  endif
#else
#  define CopFILEGV(c)		((c)->cop_filegv)
#  define CopFILEGV_set(c,gv)	((c)->cop_filegv = (GV*)SvREFCNT_inc(gv))
#  define CopFILE_set(c,pv)	CopFILEGV_set((c), gv_fetchfile(pv))
#  define CopFILE_setn(c,pv,l)	CopFILEGV_set((c), gv_fetchfile_flags((pv),(l),0))
#  define CopFILESV(c)		(CopFILEGV(c) ? GvSV(CopFILEGV(c)) : NULL)
#  define CopFILEAV(c)		(CopFILEGV(c) ? GvAV(CopFILEGV(c)) : NULL)
#  ifdef DEBUGGING
#    define CopFILEAVx(c)	(assert(CopFILEGV(c)), GvAV(CopFILEGV(c)))
#  else
#    define CopFILEAVx(c)	(GvAV(CopFILEGV(c)))
# endif
#  define CopFILE(c)		(CopFILEGV(c) && GvSV(CopFILEGV(c)) \
				    ? SvPVX(GvSV(CopFILEGV(c))) : NULL)
#  define CopSTASH(c)		((c)->cop_stash)
#  define CopLABEL(c)		((c)->cop_label)
#  define CopSTASH_set(c,hv)	((c)->cop_stash = (hv))
#  define CopSTASHPV(c)		(CopSTASH(c) ? HvNAME_get(CopSTASH(c)) : NULL)
   /* cop_stash is not refcounted */
#  define CopSTASHPV_set(c,pv)	CopSTASH_set((c), gv_stashpv(pv,GV_ADD))
#  define CopSTASH_eq(c,hv)	(CopSTASH(c) == (hv))
#  define CopLABEL_alloc(pv)	((pv)?savepv(pv):NULL)
#  define CopLABEL_set(c,pv)	(CopLABEL(c) = (pv))
#  define CopSTASH_free(c)	
#  define CopFILE_free(c)	(SvREFCNT_dec(CopFILEGV(c)),(CopFILEGV(c) = NULL))
#  define CopLABEL_free(c)	(Safefree(CopLABEL(c)),(CopLABEL(c) = NULL))

#endif /* USE_ITHREADS */

#define CopSTASH_ne(c,hv)	(!CopSTASH_eq(c,hv))
#define CopLINE(c)		((c)->cop_line)
#define CopLINE_inc(c)		(++CopLINE(c))
#define CopLINE_dec(c)		(--CopLINE(c))
#define CopLINE_set(c,l)	(CopLINE(c) = (l))

/* OutCopFILE() is CopFILE for output (caller, die, warn, etc.) */
#ifdef MACOS_TRADITIONAL
#  define OutCopFILE(c) MacPerl_MPWFileName(CopFILE(c))
#else
#  define OutCopFILE(c) CopFILE(c)
#endif

/* If $[ is non-zero, it's stored in cop_hints under the key "$[", and
   HINT_ARYBASE is set to indicate this.
   Setting it is ineficient due to the need to create 2 mortal SVs, but as
   using $[ is highly discouraged, no sane Perl code will be using it.  */
#define CopARYBASE_get(c)	\
	((CopHINTS_get(c) & HINT_ARYBASE)				\
	 ? SvIV(Perl_refcounted_he_fetch(aTHX_ (c)->cop_hints_hash, 0,	\
					 "$[", 2, 0, 0))		\
	 : 0)
#define CopARYBASE_set(c, b) STMT_START { \
	if (b || ((c)->cop_hints & HINT_ARYBASE)) {			\
	    (c)->cop_hints |= HINT_ARYBASE;				\
	    if ((c) == &PL_compiling)					\
		PL_hints |= HINT_LOCALIZE_HH | HINT_ARYBASE;		\
	    (c)->cop_hints_hash						\
	       = Perl_refcounted_he_new(aTHX_ (c)->cop_hints_hash,	\
					sv_2mortal(newSVpvs("$[")),	\
					sv_2mortal(newSViv(b)));	\
	}								\
    } STMT_END

/* FIXME NATIVE_HINTS if this is changed from op_private (see perl.h)  */
#define CopHINTS_get(c)		((c)->cop_hints + 0)
#define CopHINTS_set(c, h)	STMT_START {				\
				    (c)->cop_hints = (h);		\
				} STMT_END

/*
 * Here we have some enormously heavy (or at least ponderous) wizardry.
 */

/* subroutine context */
struct block_sub {
    CV *	cv;
    GV *	gv;
    GV *	dfoutgv;
    AV *	savearray;
    AV *	argarray;
    I32		olddepth;
    U8		hasargs;
    U8		lval;		/* XXX merge lval and hasargs? */
    PAD		*oldcomppad;
    OP *	retop;	/* op to execute on exit from sub */
};

/* base for the next two macros. Don't use directly.
 * Note that the refcnt of the cv is incremented twice;  The CX one is
 * decremented by LEAVESUB, the other by LEAVE. */

#define PUSHSUB_BASE(cx)						\
	cx->blk_sub.cv = cv;						\
	cx->blk_sub.olddepth = CvDEPTH(cv);				\
	cx->blk_sub.hasargs = hasargs;					\
	cx->blk_sub.retop = NULL;					\
	if (!CvDEPTH(cv)) {						\
	    SvREFCNT_inc_simple_void_NN(cv);				\
	    SvREFCNT_inc_simple_void_NN(cv);				\
	    SAVEFREESV(cv);						\
	}


#define PUSHSUB(cx)							\
	PUSHSUB_BASE(cx)						\
	cx->blk_sub.lval = PL_op->op_private &                          \
	                      (OPpLVAL_INTRO|OPpENTERSUB_INARGS);

/* variant for use by OP_DBSTATE, where op_private holds hint bits */
#define PUSHSUB_DB(cx)							\
	PUSHSUB_BASE(cx)						\
	cx->blk_sub.lval = 0;


#define PUSHFORMAT(cx)							\
	cx->blk_sub.cv = cv;						\
	cx->blk_sub.gv = gv;						\
	cx->blk_sub.retop = NULL;					\
	cx->blk_sub.hasargs = 0;					\
	cx->blk_sub.dfoutgv = PL_defoutgv;				\
	SvREFCNT_inc_void(cx->blk_sub.dfoutgv)

#define POP_SAVEARRAY()						\
    STMT_START {							\
	SvREFCNT_dec(GvAV(PL_defgv));					\
	GvAV(PL_defgv) = cx->blk_sub.savearray;				\
    } STMT_END

/* junk in @_ spells trouble when cloning CVs and in pp_caller(), so don't
 * leave any (a fast av_clear(ary), basically) */
#define CLEAR_ARGARRAY(ary) \
    STMT_START {							\
	AvMAX(ary) += AvARRAY(ary) - AvALLOC(ary);			\
	AvARRAY(ary) = AvALLOC(ary);					\
	AvFILLp(ary) = -1;						\
    } STMT_END

#define POPSUB(cx,sv)							\
    STMT_START {							\
	if (cx->blk_sub.hasargs) {					\
	    POP_SAVEARRAY();						\
	    /* abandon @_ if it got reified */				\
	    if (AvREAL(cx->blk_sub.argarray)) {				\
		const SSize_t fill = AvFILLp(cx->blk_sub.argarray);	\
		SvREFCNT_dec(cx->blk_sub.argarray);			\
		cx->blk_sub.argarray = newAV();				\
		av_extend(cx->blk_sub.argarray, fill);			\
		AvREIFY_only(cx->blk_sub.argarray);			\
		CX_CURPAD_SV(cx->blk_sub, 0) = (SV*)cx->blk_sub.argarray;	\
	    }								\
	    else {							\
		CLEAR_ARGARRAY(cx->blk_sub.argarray);			\
	    }								\
	}								\
	sv = (SV*)cx->blk_sub.cv;					\
	if (sv && (CvDEPTH((CV*)sv) = cx->blk_sub.olddepth))		\
	    sv = NULL;						\
    } STMT_END

#define LEAVESUB(sv)							\
    STMT_START {							\
	if (sv)								\
	    SvREFCNT_dec(sv);						\
    } STMT_END

#define POPFORMAT(cx)							\
	setdefout(cx->blk_sub.dfoutgv);					\
	SvREFCNT_dec(cx->blk_sub.dfoutgv);

/* eval context */
struct block_eval {
    U8		old_in_eval;
    U16		old_op_type;
    SV *	old_namesv;
    OP *	old_eval_root;
    SV *	cur_text;
    CV *	cv;
    OP *	retop;	/* op to execute on exit from eval */
    JMPENV *	cur_top_env; /* value of PL_top_env when eval CX created */
};

#define PUSHEVAL(cx,n,fgv)						\
    STMT_START {							\
	cx->blk_eval.old_in_eval = PL_in_eval;				\
	cx->blk_eval.old_op_type = PL_op->op_type;			\
	cx->blk_eval.old_namesv = (n ? newSVpv(n,0) : NULL);		\
	cx->blk_eval.old_eval_root = PL_eval_root;			\
	cx->blk_eval.cur_text = PL_parser ? PL_parser->linestr : NULL;	\
	cx->blk_eval.cv = NULL; /* set by doeval(), as applicable */	\
	cx->blk_eval.retop = NULL;					\
	cx->blk_eval.cur_top_env = PL_top_env; 				\
    } STMT_END

#define POPEVAL(cx)							\
    STMT_START {							\
	PL_in_eval = cx->blk_eval.old_in_eval;				\
	optype = cx->blk_eval.old_op_type;				\
	PL_eval_root = cx->blk_eval.old_eval_root;			\
	if (cx->blk_eval.old_namesv)					\
	    sv_2mortal(cx->blk_eval.old_namesv);			\
    } STMT_END

/* loop context */
struct block_loop {
    char *	label;
    I32		resetsp;
    LOOP *	my_op;	/* My op, that contains redo, next and last ops.  */
    /* (except for non_ithreads we need to modify next_op in pp_ctl.c, hence
	why next_op is conditionally defined below.)  */
#ifdef USE_ITHREADS
    void *	iterdata;
    PAD		*oldcomppad;
#else
    OP *	next_op;
    SV **	itervar;
#endif
    SV *	itersave;
    /* (from inspection of source code) for a .. range of strings this is the
       current string.  */
    SV *	iterlval;
    /* (from inspection of source code) for a foreach loop this is the array
       being iterated over. For a .. range of numbers it's the current value.
       A check is often made on the SvTYPE of iterary to determine whether
       we are iterating over an array or a range. (numbers or strings)  */
    AV *	iterary;
    IV		iterix;
    /* (from inspection of source code) for a .. range of numbers this is the
       maximum value.  */
    IV		itermax;
};
/* It might be possible to squeeze this structure further. As best I can tell
   itermax and iterlval are never used at the same time, so it might be possible
   to make them into a union. However, I'm not confident that there are enough
   flag bits/NULLable pointers in this structure alone to encode which is
   active. There is, however, U8 of space free in struct block, which could be
   used. Right now it may not be worth squeezing this structure further, as it's
   the largest part of struct block, and currently struct block is 64 bytes on
   an ILP32 system, which will give good cache alignment.
*/

#ifdef USE_ITHREADS
#  define CxITERVAR(c)							\
	((c)->blk_loop.iterdata						\
	 ? (CxPADLOOP(cx) 						\
	    ? &CX_CURPAD_SV( (c)->blk_loop, 				\
		    INT2PTR(PADOFFSET, (c)->blk_loop.iterdata))		\
	    : &GvSV((GV*)(c)->blk_loop.iterdata))			\
	 : (SV**)NULL)
#  define CX_ITERDATA_SET(cx,idata)					\
	CX_CURPAD_SAVE(cx->blk_loop);					\
	if ((cx->blk_loop.iterdata = (idata)))				\
	    cx->blk_loop.itersave = SvREFCNT_inc(*CxITERVAR(cx));	\
	else								\
	    cx->blk_loop.itersave = NULL;
#else
#  define CxITERVAR(c)		((c)->blk_loop.itervar)
#  define CX_ITERDATA_SET(cx,ivar)					\
	if ((cx->blk_loop.itervar = (SV**)(ivar)))			\
	    cx->blk_loop.itersave = SvREFCNT_inc(*CxITERVAR(cx));	\
	else								\
	    cx->blk_loop.itersave = NULL;
#endif

#ifdef USE_ITHREADS
#  define PUSHLOOP_OP_NEXT		/* No need to do anything.  */
#  define CX_LOOP_NEXTOP_GET(cx)	((cx)->blk_loop.my_op->op_nextop + 0)
#else
#  define PUSHLOOP_OP_NEXT		cx->blk_loop.next_op = cLOOP->op_nextop
#  define CX_LOOP_NEXTOP_GET(cx)	((cx)->blk_loop.next_op + 0)
#endif

#define PUSHLOOP(cx, dat, s)						\
	cx->blk_loop.label = PL_curcop->cop_label;			\
	cx->blk_loop.resetsp = s - PL_stack_base;			\
	cx->blk_loop.my_op = cLOOP;					\
	PUSHLOOP_OP_NEXT;						\
	cx->blk_loop.iterlval = NULL;					\
	cx->blk_loop.iterary = NULL;					\
	cx->blk_loop.iterix = -1;					\
	CX_ITERDATA_SET(cx,dat);

#define POPLOOP(cx)							\
	SvREFCNT_dec(cx->blk_loop.iterlval);				\
	if (CxITERVAR(cx)) {						\
            if (SvPADMY(cx->blk_loop.itersave)) {			\
		SV ** const s_v_p = CxITERVAR(cx);			\
		sv_2mortal(*s_v_p);					\
		*s_v_p = cx->blk_loop.itersave;				\
	    }								\
	    else {							\
		SvREFCNT_dec(cx->blk_loop.itersave);			\
	    }								\
	}								\
	if (cx->blk_loop.iterary && cx->blk_loop.iterary != PL_curstack)\
	    SvREFCNT_dec(cx->blk_loop.iterary);

/* given/when context */
struct block_givwhen {
	OP *leave_op;
};

#define PUSHGIVEN(cx)							\
	cx->blk_givwhen.leave_op = cLOGOP->op_other;

#define PUSHWHEN PUSHGIVEN

/* context common to subroutines, evals and loops */
struct block {
    U16		blku_type;	/* what kind of context this is */
    U8		blku_gimme;	/* is this block running in list context? */
    U8		blku_spare;	/* Padding to match with struct subst */
    I32		blku_oldsp;	/* stack pointer to copy stuff down to */
    COP *	blku_oldcop;	/* old curcop pointer */
    I32		blku_oldmarksp;	/* mark stack index */
    I32		blku_oldscopesp;	/* scope stack index */
    PMOP *	blku_oldpm;	/* values of pattern match vars */

    union {
	struct block_sub	blku_sub;
	struct block_eval	blku_eval;
	struct block_loop	blku_loop;
	struct block_givwhen	blku_givwhen;
    } blk_u;
};
#define blk_oldsp	cx_u.cx_blk.blku_oldsp
#define blk_oldcop	cx_u.cx_blk.blku_oldcop
#define blk_oldmarksp	cx_u.cx_blk.blku_oldmarksp
#define blk_oldscopesp	cx_u.cx_blk.blku_oldscopesp
#define blk_oldpm	cx_u.cx_blk.blku_oldpm
#define blk_gimme	cx_u.cx_blk.blku_gimme
#define blk_sub		cx_u.cx_blk.blk_u.blku_sub
#define blk_eval	cx_u.cx_blk.blk_u.blku_eval
#define blk_loop	cx_u.cx_blk.blk_u.blku_loop
#define blk_givwhen	cx_u.cx_blk.blk_u.blku_givwhen

/* Enter a block. */
#define PUSHBLOCK(cx,t,sp) CXINC, cx = &cxstack[cxstack_ix],		\
	cx->cx_type		= t,					\
	cx->blk_oldsp		= sp - PL_stack_base,			\
	cx->blk_oldcop		= PL_curcop,				\
	cx->blk_oldmarksp	= PL_markstack_ptr - PL_markstack,	\
	cx->blk_oldscopesp	= PL_scopestack_ix,			\
	cx->blk_oldpm		= PL_curpm,				\
	cx->blk_gimme		= (U8)gimme;				\
	DEBUG_l( PerlIO_printf(Perl_debug_log, "Entering block %ld, type %s\n",	\
		    (long)cxstack_ix, PL_block_type[CxTYPE(cx)]); )

/* Exit a block (RETURN and LAST). */
#define POPBLOCK(cx,pm) cx = &cxstack[cxstack_ix--],			\
	newsp		 = PL_stack_base + cx->blk_oldsp,		\
	PL_curcop	 = cx->blk_oldcop,				\
	PL_markstack_ptr = PL_markstack + cx->blk_oldmarksp,		\
	PL_scopestack_ix = cx->blk_oldscopesp,				\
	pm		 = cx->blk_oldpm,				\
	gimme		 = cx->blk_gimme;				\
	DEBUG_SCOPE("POPBLOCK");					\
	DEBUG_l( PerlIO_printf(Perl_debug_log, "Leaving block %ld, type %s\n",		\
		    (long)cxstack_ix+1,PL_block_type[CxTYPE(cx)]); )

/* Continue a block elsewhere (NEXT and REDO). */
#define TOPBLOCK(cx) cx  = &cxstack[cxstack_ix],			\
	PL_stack_sp	 = PL_stack_base + cx->blk_oldsp,		\
	PL_markstack_ptr = PL_markstack + cx->blk_oldmarksp,		\
	PL_scopestack_ix = cx->blk_oldscopesp,				\
	PL_curpm         = cx->blk_oldpm;				\
	DEBUG_SCOPE("TOPBLOCK");

/* substitution context */
struct subst {
    U16		sbu_type;	/* what kind of context this is */
    U8		sbu_once;	/* Actually both booleans, but U8 to matches */
    U8		sbu_rxtainted;	/* struct block */
    I32		sbu_iters;
    I32		sbu_maxiters;
    I32		sbu_rflags;
    I32		sbu_oldsave;
    char *	sbu_orig;
    SV *	sbu_dstr;
    SV *	sbu_targ;
    char *	sbu_s;
    char *	sbu_m;
    char *	sbu_strend;
    void *	sbu_rxres;
    REGEXP *	sbu_rx;
};
#define sb_iters	cx_u.cx_subst.sbu_iters
#define sb_maxiters	cx_u.cx_subst.sbu_maxiters
#define sb_rflags	cx_u.cx_subst.sbu_rflags
#define sb_oldsave	cx_u.cx_subst.sbu_oldsave
#define sb_once		cx_u.cx_subst.sbu_once
#define sb_rxtainted	cx_u.cx_subst.sbu_rxtainted
#define sb_orig		cx_u.cx_subst.sbu_orig
#define sb_dstr		cx_u.cx_subst.sbu_dstr
#define sb_targ		cx_u.cx_subst.sbu_targ
#define sb_s		cx_u.cx_subst.sbu_s
#define sb_m		cx_u.cx_subst.sbu_m
#define sb_strend	cx_u.cx_subst.sbu_strend
#define sb_rxres	cx_u.cx_subst.sbu_rxres
#define sb_rx		cx_u.cx_subst.sbu_rx

#define PUSHSUBST(cx) CXINC, cx = &cxstack[cxstack_ix],			\
	cx->sb_iters		= iters,				\
	cx->sb_maxiters		= maxiters,				\
	cx->sb_rflags		= r_flags,				\
	cx->sb_oldsave		= oldsave,				\
	cx->sb_once		= once,					\
	cx->sb_rxtainted	= rxtainted,				\
	cx->sb_orig		= orig,					\
	cx->sb_dstr		= dstr,					\
	cx->sb_targ		= targ,					\
	cx->sb_s		= s,					\
	cx->sb_m		= m,					\
	cx->sb_strend		= strend,				\
	cx->sb_rxres		= NULL,					\
	cx->sb_rx		= rx,					\
	cx->cx_type		= CXt_SUBST;				\
	rxres_save(&cx->sb_rxres, rx);					\
	(void)ReREFCNT_inc(rx)

#define POPSUBST(cx) cx = &cxstack[cxstack_ix--];			\
	rxres_free(&cx->sb_rxres);					\
	ReREFCNT_dec(cx->sb_rx)

struct context {
    union {
	struct block	cx_blk;
	struct subst	cx_subst;
    } cx_u;
};
#define cx_type cx_u.cx_subst.sbu_type

#define CXTYPEMASK	0xff
#define CXt_NULL	0
#define CXt_SUB		1
#define CXt_EVAL	2
#define CXt_LOOP	3
#define CXt_SUBST	4
#define CXt_BLOCK	5
#define CXt_FORMAT	6
#define CXt_GIVEN	7
#define CXt_WHEN	8

/* private flags for CXt_SUB and CXt_NULL */
#define CXp_MULTICALL	0x00000400	/* part of a multicall (so don't
					   tear down context on exit). */ 

/* private flags for CXt_EVAL */
#define CXp_REAL	0x00000100	/* truly eval'', not a lookalike */
#define CXp_TRYBLOCK	0x00000200	/* eval{}, not eval'' or similar */

/* private flags for CXt_LOOP */
#define CXp_FOREACH	0x00000200	/* a foreach loop */
#define CXp_FOR_DEF	0x00000400	/* foreach using $_ */
#ifdef USE_ITHREADS
#  define CXp_PADVAR	0x00000100	/* itervar lives on pad, iterdata
					   has pad offset; if not set,
					   iterdata holds GV* */
#  define CxPADLOOP(c)	(((c)->cx_type & (CXt_LOOP|CXp_PADVAR))		\
			 == (CXt_LOOP|CXp_PADVAR))
#endif

#define CxTYPE(c)	((c)->cx_type & CXTYPEMASK)
#define CxMULTICALL(c)	(((c)->cx_type & CXp_MULTICALL)			\
			 == CXp_MULTICALL)
#define CxREALEVAL(c)	(((c)->cx_type & (CXt_EVAL|CXp_REAL))		\
			 == (CXt_EVAL|CXp_REAL))
#define CxTRYBLOCK(c)	(((c)->cx_type & (CXt_EVAL|CXp_TRYBLOCK))	\
			 == (CXt_EVAL|CXp_TRYBLOCK))
#define CxFOREACH(c)	(((c)->cx_type & (CXt_LOOP|CXp_FOREACH))	\
                         == (CXt_LOOP|CXp_FOREACH))
#define CxFOREACHDEF(c)	(((c)->cx_type & (CXt_LOOP|CXp_FOREACH|CXp_FOR_DEF))\
			 == (CXt_LOOP|CXp_FOREACH|CXp_FOR_DEF))

#define CXINC (cxstack_ix < cxstack_max ? ++cxstack_ix : (cxstack_ix = cxinc()))

/* 
=head1 "Gimme" Values
*/

/*
=for apidoc AmU||G_SCALAR
Used to indicate scalar context.  See C<GIMME_V>, C<GIMME>, and
L<perlcall>.

=for apidoc AmU||G_ARRAY
Used to indicate list context.  See C<GIMME_V>, C<GIMME> and
L<perlcall>.

=for apidoc AmU||G_VOID
Used to indicate void context.  See C<GIMME_V> and L<perlcall>.

=for apidoc AmU||G_DISCARD
Indicates that arguments returned from a callback should be discarded.  See
L<perlcall>.

=for apidoc AmU||G_EVAL

Used to force a Perl C<eval> wrapper around a callback.  See
L<perlcall>.

=for apidoc AmU||G_NOARGS

Indicates that no arguments are being sent to a callback.  See
L<perlcall>.

=cut
*/

#define G_SCALAR	0
#define G_ARRAY		1
#define G_VOID		128	/* skip this bit when adding flags below */

/* extra flags for Perl_call_* routines */
#define G_DISCARD	2	/* Call FREETMPS.
				   Don't change this without consulting the
				   hash actions codes defined in hv.h */
#define G_EVAL		4	/* Assume eval {} around subroutine call. */
#define G_NOARGS	8	/* Don't construct a @_ array. */
#define G_KEEPERR      16	/* Append errors to $@, don't overwrite it */
#define G_NODEBUG      32	/* Disable debugging at toplevel.  */
#define G_METHOD       64       /* Calling method. */
#define G_FAKINGEVAL  256	/* Faking an eval context for call_sv or
				   fold_constants. */

/* flag bits for PL_in_eval */
#define EVAL_NULL	0	/* not in an eval */
#define EVAL_INEVAL	1	/* some enclosing scope is an eval */
#define EVAL_WARNONLY	2	/* used by yywarn() when calling yyerror() */
#define EVAL_KEEPERR	4	/* set by Perl_call_sv if G_KEEPERR */
#define EVAL_INREQUIRE	8	/* The code is being required. */

/* Support for switching (stack and block) contexts.
 * This ensures magic doesn't invalidate local stack and cx pointers.
 */

#define PERLSI_UNKNOWN		-1
#define PERLSI_UNDEF		0
#define PERLSI_MAIN		1
#define PERLSI_MAGIC		2
#define PERLSI_SORT		3
#define PERLSI_SIGNAL		4
#define PERLSI_OVERLOAD		5
#define PERLSI_DESTROY		6
#define PERLSI_WARNHOOK		7
#define PERLSI_DIEHOOK		8
#define PERLSI_REQUIRE		9

struct stackinfo {
    AV *		si_stack;	/* stack for current runlevel */
    PERL_CONTEXT *	si_cxstack;	/* context stack for runlevel */
    struct stackinfo *	si_prev;
    struct stackinfo *	si_next;
    I32			si_cxix;	/* current context index */
    I32			si_cxmax;	/* maximum allocated index */
    I32			si_type;	/* type of runlevel */
    I32			si_markoff;	/* offset where markstack begins for us.
					 * currently used only with DEBUGGING,
					 * but not #ifdef-ed for bincompat */
};

typedef struct stackinfo PERL_SI;

#define cxstack		(PL_curstackinfo->si_cxstack)
#define cxstack_ix	(PL_curstackinfo->si_cxix)
#define cxstack_max	(PL_curstackinfo->si_cxmax)

#ifdef DEBUGGING
#  define	SET_MARK_OFFSET \
    PL_curstackinfo->si_markoff = PL_markstack_ptr - PL_markstack
#else
#  define	SET_MARK_OFFSET NOOP
#endif

#define PUSHSTACKi(type) \
    STMT_START {							\
	PERL_SI *next = PL_curstackinfo->si_next;			\
	if (!next) {							\
	    next = new_stackinfo(32, 2048/sizeof(PERL_CONTEXT) - 1);	\
	    next->si_prev = PL_curstackinfo;				\
	    PL_curstackinfo->si_next = next;				\
	}								\
	next->si_type = type;						\
	next->si_cxix = -1;						\
	AvFILLp(next->si_stack) = 0;					\
	SWITCHSTACK(PL_curstack,next->si_stack);			\
	PL_curstackinfo = next;						\
	SET_MARK_OFFSET;						\
    } STMT_END

#define PUSHSTACK PUSHSTACKi(PERLSI_UNKNOWN)

/* POPSTACK works with PL_stack_sp, so it may need to be bracketed by
 * PUTBACK/SPAGAIN to flush/refresh any local SP that may be active */
#define POPSTACK \
    STMT_START {							\
	dSP;								\
	PERL_SI * const prev = PL_curstackinfo->si_prev;		\
	if (!prev) {							\
	    PerlIO_printf(Perl_error_log, "panic: POPSTACK\n");		\
	    my_exit(1);							\
	}								\
	SWITCHSTACK(PL_curstack,prev->si_stack);			\
	/* don't free prev here, free them all at the END{} */		\
	PL_curstackinfo = prev;						\
    } STMT_END

#define POPSTACK_TO(s) \
    STMT_START {							\
	while (PL_curstack != s) {					\
	    dounwind(-1);						\
	    POPSTACK;							\
	}								\
    } STMT_END

#define IN_PERL_COMPILETIME	(PL_curcop == &PL_compiling)
#define IN_PERL_RUNTIME		(PL_curcop != &PL_compiling)

/*
=head1 Multicall Functions

=for apidoc Ams||dMULTICALL
Declare local variables for a multicall. See L<perlcall/Lightweight Callbacks>.

=for apidoc Ams||PUSH_MULTICALL
Opening bracket for a lightweight callback.
See L<perlcall/Lightweight Callbacks>.

=for apidoc Ams||MULTICALL
Make a lightweight callback. See L<perlcall/Lightweight Callbacks>.

=for apidoc Ams||POP_MULTICALL
Closing bracket for a lightweight callback.
See L<perlcall/Lightweight Callbacks>.

=cut
*/

#define dMULTICALL \
    SV **newsp;			/* set by POPBLOCK */			\
    PERL_CONTEXT *cx;							\
    CV *multicall_cv;							\
    OP *multicall_cop;							\
    bool multicall_oldcatch; 						\
    U8 hasargs = 0		/* used by PUSHSUB */

#define PUSH_MULTICALL(the_cv) \
    STMT_START {							\
	CV * const _nOnclAshIngNamE_ = the_cv;				\
	CV * const cv = _nOnclAshIngNamE_;				\
	AV * const padlist = CvPADLIST(cv);				\
	ENTER;								\
 	multicall_oldcatch = CATCH_GET;					\
	SAVETMPS; SAVEVPTR(PL_op);					\
	CATCH_SET(TRUE);						\
	PUSHBLOCK(cx, CXt_SUB|CXp_MULTICALL, PL_stack_sp);		\
	PUSHSUB(cx);							\
	if (++CvDEPTH(cv) >= 2) {					\
	    PERL_STACK_OVERFLOW_CHECK();				\
	    Perl_pad_push(aTHX_ padlist, CvDEPTH(cv));			\
	}								\
	SAVECOMPPAD();							\
	PAD_SET_CUR_NOSAVE(padlist, CvDEPTH(cv));			\
	multicall_cv = cv;						\
	multicall_cop = CvSTART(cv);					\
    } STMT_END

#define MULTICALL \
    STMT_START {							\
	PL_op = multicall_cop;						\
	CALLRUNOPS(aTHX);						\
    } STMT_END

#define POP_MULTICALL \
    STMT_START {							\
	LEAVESUB(multicall_cv);						\
	CvDEPTH(multicall_cv)--;					\
	POPBLOCK(cx,PL_curpm);						\
	CATCH_SET(multicall_oldcatch);					\
	LEAVE;								\
    } STMT_END

/*
 * Local variables:
 * c-indentation-style: bsd
 * c-basic-offset: 4
 * indent-tabs-mode: t
 * End:
 *
 * ex: set ts=8 sts=4 sw=4 noet:
 */
