[perl5.git] / cv.h

/*    cv.h
 *
 *    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999,
 *    2000, 2001, 2002, 2003, 2004, 2005, 2006, 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.
 *
 */

/* This structure must the beginning of XPVFM in sv.h  */

struct xpvcv {
    union {
	NV	xnv_nv;		/* numeric value, if any */
	HV *	xgv_stash;
    }		xnv_u;
    STRLEN	xpv_cur;	/* length of xp_pv as a C string */
    STRLEN	xpv_len;	/* allocated size */
    union {
	IV	xivu_iv;
	UV	xivu_uv;
	void *	xivu_p1;
	I32	xivu_i32;	/* depth, >= 2 indicates recursive call */
	HEK *	xivu_namehek;
    }		xiv_u;
    union {
	MAGIC*	xmg_magic;	/* linked list of magicalness */
	HV*	xmg_ourstash;	/* Stash for our (when SvPAD_OUR is true) */
    } xmg_u;
    HV*		xmg_stash;	/* class package */

    HV *	xcv_stash;
    union {
	OP *	xcv_start;
	ANY	xcv_xsubany;
    }		xcv_start_u;
    union {
	OP *	xcv_root;
	void	(*xcv_xsub) (pTHX_ CV*);
    }		xcv_root_u;
    GV *	xcv_gv;
    char *	xcv_file;
    PADLIST *	xcv_padlist;
    CV *	xcv_outside;
    U32		xcv_outside_seq; /* the COP sequence (at the point of our
				  * compilation) in the lexically enclosing
				  * sub */
    cv_flags_t	xcv_flags;
};

typedef struct {
    STRLEN	xpv_cur;	/* length of xp_pv as a C string */
    STRLEN	xpv_len;	/* allocated size */
    union {
	IV	xivu_iv;
	UV	xivu_uv;
	void *	xivu_p1;
	I32	xivu_i32;	/* depth, >= 2 indicates recursive call */
	HEK *	xivu_namehek;
    }		xiv_u;
    union {
	MAGIC*	xmg_magic;	/* linked list of magicalness */
	HV*	xmg_ourstash;	/* Stash for our (when SvPAD_OUR is true) */
    } xmg_u;
    HV*		xmg_stash;	/* class package */

    HV *	xcv_stash;
    union {
	OP *	xcv_start;
	ANY	xcv_xsubany;
    }		xcv_start_u;
    union {
	OP *	xcv_root;
	void	(*xcv_xsub) (pTHX_ CV*);
    }		xcv_root_u;
    GV *	xcv_gv;
    char *	xcv_file;
    PADLIST *	xcv_padlist;
    CV *	xcv_outside;
    U32		xcv_outside_seq; /* the COP sequence (at the point of our
				  * compilation) in the lexically enclosing
				  * sub */
    cv_flags_t	xcv_flags;
} xpvcv_allocated;

/*
=head1 Handy Values

=for apidoc AmU||Nullcv
Null CV pointer.

=head1 CV Manipulation Functions

=for apidoc Am|HV*|CvSTASH|CV* cv
Returns the stash of the CV.

=cut
*/

#define Nullcv Null(CV*)

#define CvSTASH(sv)	((XPVCV*)SvANY(sv))->xcv_stash
#define CvSTART(sv)	((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
#define CvROOT(sv)	((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
#define CvXSUB(sv)	((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
#define CvXSUBANY(sv)	((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
#define CvGV(sv)	((XPVCV*)SvANY(sv))->xcv_gv
#define CvFILE(sv)	((XPVCV*)SvANY(sv))->xcv_file
#ifdef USE_ITHREADS
#  define CvFILE_set_from_cop(sv, cop)	(CvFILE(sv) = savepv(CopFILE(cop)))
#else
#  define CvFILE_set_from_cop(sv, cop)	(CvFILE(sv) = CopFILE(cop))
#endif
#define CvFILEGV(sv)	(gv_fetchfile(CvFILE(sv)))
#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
#  define CvDEPTH(sv) (*({const CV *_cv = (CV *)sv; \
			  assert(SvTYPE(_cv) == SVt_PVCV); \
			  &((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
			}))
#else
#  define CvDEPTH(sv)	((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
#endif
#define CvPADLIST(sv)	((XPVCV*)SvANY(sv))->xcv_padlist
#define CvOUTSIDE(sv)	((XPVCV*)SvANY(sv))->xcv_outside
#define CvFLAGS(sv)	((XPVCV*)SvANY(sv))->xcv_flags
#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq

#define CVf_METHOD	0x0001	/* CV is explicitly marked as a method */
#define CVf_LOCKED	0x0002	/* CV locks itself or first arg on entry */
#define CVf_LVALUE	0x0004  /* CV return value can be used as lvalue */
#define CVf_ASSERTION   0x0008  /* CV called only when asserting */

#define CVf_WEAKOUTSIDE	0x0010  /* CvOUTSIDE isn't ref counted */
#define CVf_CLONE	0x0020	/* anon CV uses external lexicals */
#define CVf_CLONED	0x0040	/* a clone of one of those */
#define CVf_ANON	0x0080	/* CvGV() can't be trusted */
#define CVf_UNIQUE	0x0100	/* sub is only called once (eg PL_main_cv,
				 * require, eval). Not to be confused
				 * with the GVf_UNIQUE flag associated
				 * with the :unique attribute */
#define CVf_NODEBUG	0x0200	/* no DB::sub indirection for this CV
				   (esp. useful for special XSUBs) */
#define CVf_CONST	0x0400  /* inlinable sub */
#define CVf_ISXSUB	0x0800	/* CV is an XSUB, not pure perl.  */

/* This symbol for optimised communication between toke.c and op.c: */
#define CVf_BUILTIN_ATTRS	(CVf_METHOD|CVf_LOCKED|CVf_LVALUE|CVf_ASSERTION)

#define CvCLONE(cv)		(CvFLAGS(cv) & CVf_CLONE)
#define CvCLONE_on(cv)		(CvFLAGS(cv) |= CVf_CLONE)
#define CvCLONE_off(cv)		(CvFLAGS(cv) &= ~CVf_CLONE)

#define CvCLONED(cv)		(CvFLAGS(cv) & CVf_CLONED)
#define CvCLONED_on(cv)		(CvFLAGS(cv) |= CVf_CLONED)
#define CvCLONED_off(cv)	(CvFLAGS(cv) &= ~CVf_CLONED)

#define CvANON(cv)		(CvFLAGS(cv) & CVf_ANON)
#define CvANON_on(cv)		(CvFLAGS(cv) |= CVf_ANON)
#define CvANON_off(cv)		(CvFLAGS(cv) &= ~CVf_ANON)

#define CvUNIQUE(cv)		(CvFLAGS(cv) & CVf_UNIQUE)
#define CvUNIQUE_on(cv)		(CvFLAGS(cv) |= CVf_UNIQUE)
#define CvUNIQUE_off(cv)	(CvFLAGS(cv) &= ~CVf_UNIQUE)

#define CvNODEBUG(cv)		(CvFLAGS(cv) & CVf_NODEBUG)
#define CvNODEBUG_on(cv)	(CvFLAGS(cv) |= CVf_NODEBUG)
#define CvNODEBUG_off(cv)	(CvFLAGS(cv) &= ~CVf_NODEBUG)

#define CvMETHOD(cv)		(CvFLAGS(cv) & CVf_METHOD)
#define CvMETHOD_on(cv)		(CvFLAGS(cv) |= CVf_METHOD)
#define CvMETHOD_off(cv)	(CvFLAGS(cv) &= ~CVf_METHOD)

#define CvLOCKED(cv)		(CvFLAGS(cv) & CVf_LOCKED)
#define CvLOCKED_on(cv)		(CvFLAGS(cv) |= CVf_LOCKED)
#define CvLOCKED_off(cv)	(CvFLAGS(cv) &= ~CVf_LOCKED)

#define CvLVALUE(cv)		(CvFLAGS(cv) & CVf_LVALUE)
#define CvLVALUE_on(cv)		(CvFLAGS(cv) |= CVf_LVALUE)
#define CvLVALUE_off(cv)	(CvFLAGS(cv) &= ~CVf_LVALUE)

#define CvASSERTION(cv)		(CvFLAGS(cv) & CVf_ASSERTION)
#define CvASSERTION_on(cv)	(CvFLAGS(cv) |= CVf_ASSERTION)
#define CvASSERTION_off(cv)	(CvFLAGS(cv) &= ~CVf_ASSERTION)

#define CvEVAL(cv)		(CvUNIQUE(cv) && !SvFAKE(cv))
#define CvEVAL_on(cv)		(CvUNIQUE_on(cv),SvFAKE_off(cv))
#define CvEVAL_off(cv)		CvUNIQUE_off(cv)

/* BEGIN|CHECK|INIT|END */
#define CvSPECIAL(cv)		(CvUNIQUE(cv) && SvFAKE(cv))
#define CvSPECIAL_on(cv)	(CvUNIQUE_on(cv),SvFAKE_on(cv))
#define CvSPECIAL_off(cv)	(CvUNIQUE_off(cv),SvFAKE_off(cv))

#define CvCONST(cv)		(CvFLAGS(cv) & CVf_CONST)
#define CvCONST_on(cv)		(CvFLAGS(cv) |= CVf_CONST)
#define CvCONST_off(cv)		(CvFLAGS(cv) &= ~CVf_CONST)

#define CvWEAKOUTSIDE(cv)	(CvFLAGS(cv) & CVf_WEAKOUTSIDE)
#define CvWEAKOUTSIDE_on(cv)	(CvFLAGS(cv) |= CVf_WEAKOUTSIDE)
#define CvWEAKOUTSIDE_off(cv)	(CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)

#define CvISXSUB(cv)		(CvFLAGS(cv) & CVf_ISXSUB)
#define CvISXSUB_on(cv)		(CvFLAGS(cv) |= CVf_ISXSUB)
#define CvISXSUB_off(cv)	(CvFLAGS(cv) &= ~CVf_ISXSUB)

/*
=head1 CV reference counts and CvOUTSIDE

=for apidoc m|bool|CvWEAKOUTSIDE|CV *cv

Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
CV (if any). Because pointers to anonymous sub prototypes are
stored in C<&> pad slots, it is a possible to get a circular reference,
with the parent pointing to the child and vice-versa. To avoid the
ensuing memory leak, we do not increment the reference count of the CV
pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
has a C<&> pad slot pointing back to us. In this case, we set the
C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
circumstances we should decrement the refcount of the parent when freeing
the child.

There is a further complication with non-closure anonymous subs (i.e. those
that do not refer to any lexicals outside that sub). In this case, the
anonymous prototype is shared rather than being cloned. This has the
consequence that the parent may be freed while there are still active
children, eg

    BEGIN { $a = sub { eval '$x' } }

In this case, the BEGIN is freed immediately after execution since there
are no active references to it: the anon sub prototype has
C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
CV, so it doesn't contribute to BEGIN's refcount either.  When $a is
executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
and the freed BEGIN is accessed.

To avoid this, whenever a CV and its associated pad is freed, any
C<&> entries in the pad are explicitly removed from the pad, and if the
refcount of the pointed-to anon sub is still positive, then that
child's C<CvOUTSIDE> is set to point to its grandparent. This will only
occur in the single specific case of a non-closure anon prototype
having one or more active references (such as C<$a> above).

One other thing to consider is that a CV may be merely undefined
rather than freed, eg C<undef &foo>. In this case, its refcount may
not have reached zero, but we still delete its pad and its C<CvROOT> etc.
Since various children may still have their C<CvOUTSIDE> pointing at this
undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
the chain of lexical scopes is unbroken. For example, the following
should print 123:

    my $x = 123;
    sub tmp { sub { eval '$x' } }
    my $a = tmp();
    undef &tmp;
    print  $a->();

=cut
*/

/*
 * Local variables:
 * c-indentation-style: bsd
 * c-basic-offset: 4
 * indent-tabs-mode: t
 * End:
 *
 * ex: set ts=8 sts=4 sw=4 noet:
 */
Commit	Line	Data
a0d0e21e	1	/* cv.h
79072805	2	*
4bb101f2	3	* Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1999,
bf53b3a5	4	* 2000, 2001, 2002, 2003, 2004, 2005, 2006, by Larry Wall and others
79072805 LW	5	*
	6	* You may distribute under the terms of either the GNU General Public
	7	* License or the Artistic License, as specified in the README file.
	8	*
79072805 LW	9	*/
79072805 LW	10
7c60e434	11	/* This structure must the beginning of XPVFM in sv.h */
44a8e56a	12
79072805	13	struct xpvcv {
58430790 NC	14	union {
	15	NV xnv_nv; /* numeric value, if any */
	16	HV * xgv_stash;
	17	} xnv_u;
79072805 LW	18	STRLEN xpv_cur; /* length of xp_pv as a C string */
79072805 LW	19	STRLEN xpv_len; /* allocated size */
e4305a63	20	union {
bb172083	21	IV xivu_iv;
311a25d9 NC	22	UV xivu_uv;
311a25d9 NC	23	void * xivu_p1;
bb172083	24	I32 xivu_i32; /* depth, >= 2 indicates recursive call */
69ecfd12	25	HEK * xivu_namehek;
311a25d9	26	} xiv_u;
e736a858 NC	27	union {
	28	MAGIC* xmg_magic; /* linked list of magicalness */
	29	HV* xmg_ourstash; /* Stash for our (when SvPAD_OUR is true) */
	30	} xmg_u;
79072805 LW	31	HV* xmg_stash; /* class package */
	32
	33	HV * xcv_stash;
bf53b3a5 NC	34	union {
	35	OP * xcv_start;
	36	ANY xcv_xsubany;
	37	} xcv_start_u;
d04ba589 NC	38	union {
	39	OP * xcv_root;
	40	void (xcv_xsub) (pTHX_ CV);
	41	} xcv_root_u;
8990e307	42	GV * xcv_gv;
57843af0	43	char * xcv_file;
dd2155a4	44	PADLIST * xcv_padlist;
748a9306	45	CV * xcv_outside;
a3985cdc DM	46	U32 xcv_outside_seq; /* the COP sequence (at the point of our
	47	* compilation) in the lexically enclosing
	48	* sub */
bb172083	49	cv_flags_t xcv_flags;
79072805	50	};
748a9306	51
c84c4652 NC	52	typedef struct {
	53	STRLEN xpv_cur; /* length of xp_pv as a C string */
	54	STRLEN xpv_len; /* allocated size */
	55	union {
	56	IV xivu_iv;
	57	UV xivu_uv;
	58	void * xivu_p1;
	59	I32 xivu_i32; /* depth, >= 2 indicates recursive call */
69ecfd12	60	HEK * xivu_namehek;
c84c4652	61	} xiv_u;
e736a858 NC	62	union {
	63	MAGIC* xmg_magic; /* linked list of magicalness */
	64	HV* xmg_ourstash; /* Stash for our (when SvPAD_OUR is true) */
	65	} xmg_u;
c84c4652 NC	66	HV* xmg_stash; /* class package */
	67
	68	HV * xcv_stash;
	69	union {
	70	OP * xcv_start;
	71	ANY xcv_xsubany;
	72	} xcv_start_u;
	73	union {
	74	OP * xcv_root;
	75	void (xcv_xsub) (pTHX_ CV);
	76	} xcv_root_u;
	77	GV * xcv_gv;
	78	char * xcv_file;
	79	PADLIST * xcv_padlist;
	80	CV * xcv_outside;
	81	U32 xcv_outside_seq; /* the COP sequence (at the point of our
	82	* compilation) in the lexically enclosing
	83	* sub */
	84	cv_flags_t xcv_flags;
	85	} xpvcv_allocated;
	86
954c1994	87	/*
ccfc67b7 JH	88	=head1 Handy Values
ccfc67b7 JH	89
954c1994 GS	90	=for apidoc AmU\|\|Nullcv
	91	Null CV pointer.
	92
ccfc67b7 JH	93	=head1 CV Manipulation Functions
ccfc67b7 JH	94
954c1994 GS	95	=for apidoc Am\|HV\|CvSTASH\|CV cv
	96	Returns the stash of the CV.
	97
	98	=cut
	99	*/
	100
79072805	101	#define Nullcv Null(CV*)
a5f75d66	102
79072805	103	#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5	104	#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
d04ba589 NC	105	#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
d04ba589 NC	106	#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
bf53b3a5	107	#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307	108	#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0	109	#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
a636914a RH	110	#ifdef USE_ITHREADS
	111	# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
	112	#else
	113	# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
	114	#endif
9ec2a764	115	#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
bb172083 NC	116	#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
	117	# define CvDEPTH(sv) (({const CV _cv = (CV *)sv; \
	118	assert(SvTYPE(_cv) == SVt_PVCV); \
	119	&((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
	120	}))
	121	#else
	122	# define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
	123	#endif
79072805	124	#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306	125	#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66	126	#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc	127	#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66	128
5b4563c8 NC	129	#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
	130	#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
	131	#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
	132	#define CVf_ASSERTION 0x0008 /* CV called only when asserting */
	133
	134	#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
	135	#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
	136	#define CVf_CLONED 0x0040 /* a clone of one of those */
	137	#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
	138	#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
6909cc55 DM	139	* require, eval). Not to be confused
	140	* with the GVf_UNIQUE flag associated
	141	* with the :unique attribute */
5b4563c8	142	#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01	143	(esp. useful for special XSUBs) */
5b4563c8	144	#define CVf_CONST 0x0400 /* inlinable sub */
f73ef291	145	#define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */
7dafbf52	146
d3cea301	147	/* This symbol for optimised communication between toke.c and op.c: */
06492da6	148	#define CVf_BUILTIN_ATTRS (CVf_METHOD\|CVf_LOCKED\|CVf_LVALUE\|CVf_ASSERTION)
a5f75d66 AD	149
	150	#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
	151	#define CvCLONE_on(cv) (CvFLAGS(cv) \|= CVf_CLONE)
	152	#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
	153
	154	#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
	155	#define CvCLONED_on(cv) (CvFLAGS(cv) \|= CVf_CLONED)
	156	#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
	157
	158	#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
	159	#define CvANON_on(cv) (CvFLAGS(cv) \|= CVf_ANON)
	160	#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805	161
07055b4c CS	162	#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
	163	#define CvUNIQUE_on(cv) (CvFLAGS(cv) \|= CVf_UNIQUE)
	164	#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
8ebc5c01	165
	166	#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
	167	#define CvNODEBUG_on(cv) (CvFLAGS(cv) \|= CVf_NODEBUG)
	168	#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
77a005ab MB	169
	170	#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
	171	#define CvMETHOD_on(cv) (CvFLAGS(cv) \|= CVf_METHOD)
	172	#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
	173
	174	#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
	175	#define CvLOCKED_on(cv) (CvFLAGS(cv) \|= CVf_LOCKED)
	176	#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91	177
cd06dffe GS	178	#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
	179	#define CvLVALUE_on(cv) (CvFLAGS(cv) \|= CVf_LVALUE)
	180	#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
	181
06492da6 SF	182	#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
	183	#define CvASSERTION_on(cv) (CvFLAGS(cv) \|= CVf_ASSERTION)
	184	#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
	185
1aff0e91 GS	186	#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
	187	#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
	188	#define CvEVAL_off(cv) CvUNIQUE_off(cv)
	189
bec31f9a	190	/* BEGIN\|CHECK\|INIT\|END */
1aff0e91 GS	191	#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
	192	#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
	193	#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
beab0874 JT	194
	195	#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
	196	#define CvCONST_on(cv) (CvFLAGS(cv) \|= CVf_CONST)
	197	#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029	198
7dafbf52 DM	199	#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
	200	#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) \|= CVf_WEAKOUTSIDE)
	201	#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
	202
d04ba589 NC	203	#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
	204	#define CvISXSUB_on(cv) (CvFLAGS(cv) \|= CVf_ISXSUB)
	205	#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
	206
7dafbf52 DM	207	/*
	208	=head1 CV reference counts and CvOUTSIDE
	209
	210	=for apidoc m\|bool\|CvWEAKOUTSIDE\|CV *cv
	211
	212	Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
	213	CV (if any). Because pointers to anonymous sub prototypes are
	214	stored in C<&> pad slots, it is a possible to get a circular reference,
	215	with the parent pointing to the child and vice-versa. To avoid the
	216	ensuing memory leak, we do not increment the reference count of the CV
	217	pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
	218	has a C<&> pad slot pointing back to us. In this case, we set the
	219	C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
	220	circumstances we should decrement the refcount of the parent when freeing
	221	the child.
	222
eeb8d49e	223	There is a further complication with non-closure anonymous subs (i.e. those
7dafbf52 DM	224	that do not refer to any lexicals outside that sub). In this case, the
	225	anonymous prototype is shared rather than being cloned. This has the
	226	consequence that the parent may be freed while there are still active
	227	children, eg
	228
	229	BEGIN { $a = sub { eval '$x' } }
	230
	231	In this case, the BEGIN is freed immediately after execution since there
	232	are no active references to it: the anon sub prototype has
	233	C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
	234	CV, so it doesn't contribute to BEGIN's refcount either. When $a is
	235	executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
	236	and the freed BEGIN is accessed.
	237
	238	To avoid this, whenever a CV and its associated pad is freed, any
	239	C<&> entries in the pad are explicitly removed from the pad, and if the
	240	refcount of the pointed-to anon sub is still positive, then that
	241	child's C<CvOUTSIDE> is set to point to its grandparent. This will only
	242	occur in the single specific case of a non-closure anon prototype
	243	having one or more active references (such as C<$a> above).
	244
	245	One other thing to consider is that a CV may be merely undefined
	246	rather than freed, eg C<undef &foo>. In this case, its refcount may
	247	not have reached zero, but we still delete its pad and its C<CvROOT> etc.
	248	Since various children may still have their C<CvOUTSIDE> pointing at this
	249	undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
	250	the chain of lexical scopes is unbroken. For example, the following
	251	should print 123:
	252
	253	my $x = 123;
	254	sub tmp { sub { eval '$x' } }
	255	my $a = tmp();
	256	undef &tmp;
	257	print $a->();
	258
	259	=cut
	260	*/
102d3b8a NC	261
	262	/*
	263	* Local variables:
	264	* c-indentation-style: bsd
	265	* c-basic-offset: 4
	266	* indent-tabs-mode: t
	267	* End:
	268	*
	269	* ex: set ts=8 sts=4 sw=4 noet:
	270	*/