[p5sagit/p5-mst-13.2.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 */
    }		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 */
    }		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	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	9	*/
79072805	10
7c60e434	11	/* This structure must the beginning of XPVFM in sv.h */
44a8e56a	12
79072805	13	struct xpvcv {
58430790	14	union {
	15	NV xnv_nv; /* numeric value, if any */
	16	HV * xgv_stash;
	17	} xnv_u;
79072805	18	STRLEN xpv_cur; /* length of xp_pv as a C string */
79072805	19	STRLEN xpv_len; /* allocated size */
e4305a63	20	union {
bb172083	21	IV xivu_iv;
311a25d9	22	UV xivu_uv;
311a25d9	23	void * xivu_p1;
bb172083	24	I32 xivu_i32; /* depth, >= 2 indicates recursive call */
311a25d9	25	} xiv_u;
e736a858	26	union {
	27	MAGIC* xmg_magic; /* linked list of magicalness */
	28	HV* xmg_ourstash; /* Stash for our (when SvPAD_OUR is true) */
	29	} xmg_u;
79072805	30	HV* xmg_stash; /* class package */
	31
	32	HV * xcv_stash;
bf53b3a5	33	union {
	34	OP * xcv_start;
	35	ANY xcv_xsubany;
	36	} xcv_start_u;
d04ba589	37	union {
	38	OP * xcv_root;
	39	void (xcv_xsub) (pTHX_ CV);
	40	} xcv_root_u;
8990e307	41	GV * xcv_gv;
57843af0	42	char * xcv_file;
dd2155a4	43	PADLIST * xcv_padlist;
748a9306	44	CV * xcv_outside;
a3985cdc	45	U32 xcv_outside_seq; /* the COP sequence (at the point of our
	46	* compilation) in the lexically enclosing
	47	* sub */
bb172083	48	cv_flags_t xcv_flags;
79072805	49	};
748a9306	50
c84c4652	51	typedef struct {
	52	STRLEN xpv_cur; /* length of xp_pv as a C string */
	53	STRLEN xpv_len; /* allocated size */
	54	union {
	55	IV xivu_iv;
	56	UV xivu_uv;
	57	void * xivu_p1;
	58	I32 xivu_i32; /* depth, >= 2 indicates recursive call */
	59	} xiv_u;
e736a858	60	union {
	61	MAGIC* xmg_magic; /* linked list of magicalness */
	62	HV* xmg_ourstash; /* Stash for our (when SvPAD_OUR is true) */
	63	} xmg_u;
c84c4652	64	HV* xmg_stash; /* class package */
	65
	66	HV * xcv_stash;
	67	union {
	68	OP * xcv_start;
	69	ANY xcv_xsubany;
	70	} xcv_start_u;
	71	union {
	72	OP * xcv_root;
	73	void (xcv_xsub) (pTHX_ CV);
	74	} xcv_root_u;
	75	GV * xcv_gv;
	76	char * xcv_file;
	77	PADLIST * xcv_padlist;
	78	CV * xcv_outside;
	79	U32 xcv_outside_seq; /* the COP sequence (at the point of our
	80	* compilation) in the lexically enclosing
	81	* sub */
	82	cv_flags_t xcv_flags;
	83	} xpvcv_allocated;
	84
954c1994	85	/*
ccfc67b7	86	=head1 Handy Values
ccfc67b7	87
954c1994	88	=for apidoc AmU\|\|Nullcv
	89	Null CV pointer.
	90
ccfc67b7	91	=head1 CV Manipulation Functions
ccfc67b7	92
954c1994	93	=for apidoc Am\|HV\|CvSTASH\|CV cv
	94	Returns the stash of the CV.
	95
	96	=cut
	97	*/
	98
79072805	99	#define Nullcv Null(CV*)
a5f75d66	100
79072805	101	#define CvSTASH(sv) ((XPVCV*)SvANY(sv))->xcv_stash
bf53b3a5	102	#define CvSTART(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_start
d04ba589	103	#define CvROOT(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_root
d04ba589	104	#define CvXSUB(sv) ((XPVCV*)SvANY(sv))->xcv_root_u.xcv_xsub
bf53b3a5	105	#define CvXSUBANY(sv) ((XPVCV*)SvANY(sv))->xcv_start_u.xcv_xsubany
8990e307	106	#define CvGV(sv) ((XPVCV*)SvANY(sv))->xcv_gv
57843af0	107	#define CvFILE(sv) ((XPVCV*)SvANY(sv))->xcv_file
a636914a	108	#ifdef USE_ITHREADS
	109	# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = savepv(CopFILE(cop)))
	110	#else
	111	# define CvFILE_set_from_cop(sv, cop) (CvFILE(sv) = CopFILE(cop))
	112	#endif
9ec2a764	113	#define CvFILEGV(sv) (gv_fetchfile(CvFILE(sv)))
bb172083	114	#if defined(__GNUC__) && !defined(PERL_GCC_BRACE_GROUPS_FORBIDDEN)
	115	# define CvDEPTH(sv) (({const CV _cv = (CV *)sv; \
	116	assert(SvTYPE(_cv) == SVt_PVCV); \
	117	&((XPVCV*)SvANY(_cv))->xiv_u.xivu_i32; \
	118	}))
	119	#else
	120	# define CvDEPTH(sv) ((XPVCV*)SvANY(sv))->xiv_u.xivu_i32
	121	#endif
79072805	122	#define CvPADLIST(sv) ((XPVCV*)SvANY(sv))->xcv_padlist
748a9306	123	#define CvOUTSIDE(sv) ((XPVCV*)SvANY(sv))->xcv_outside
a5f75d66	124	#define CvFLAGS(sv) ((XPVCV*)SvANY(sv))->xcv_flags
a3985cdc	125	#define CvOUTSIDE_SEQ(sv) ((XPVCV*)SvANY(sv))->xcv_outside_seq
a5f75d66	126
5b4563c8	127	#define CVf_METHOD 0x0001 /* CV is explicitly marked as a method */
	128	#define CVf_LOCKED 0x0002 /* CV locks itself or first arg on entry */
	129	#define CVf_LVALUE 0x0004 /* CV return value can be used as lvalue */
	130	#define CVf_ASSERTION 0x0008 /* CV called only when asserting */
	131
	132	#define CVf_WEAKOUTSIDE 0x0010 /* CvOUTSIDE isn't ref counted */
	133	#define CVf_CLONE 0x0020 /* anon CV uses external lexicals */
	134	#define CVf_CLONED 0x0040 /* a clone of one of those */
	135	#define CVf_ANON 0x0080 /* CvGV() can't be trusted */
	136	#define CVf_UNIQUE 0x0100 /* sub is only called once (eg PL_main_cv,
6909cc55	137	* require, eval). Not to be confused
	138	* with the GVf_UNIQUE flag associated
	139	* with the :unique attribute */
5b4563c8	140	#define CVf_NODEBUG 0x0200 /* no DB::sub indirection for this CV
8ebc5c01	141	(esp. useful for special XSUBs) */
5b4563c8	142	#define CVf_CONST 0x0400 /* inlinable sub */
f73ef291	143	#define CVf_ISXSUB 0x0800 /* CV is an XSUB, not pure perl. */
7dafbf52	144
d3cea301	145	/* This symbol for optimised communication between toke.c and op.c: */
06492da6	146	#define CVf_BUILTIN_ATTRS (CVf_METHOD\|CVf_LOCKED\|CVf_LVALUE\|CVf_ASSERTION)
a5f75d66	147
	148	#define CvCLONE(cv) (CvFLAGS(cv) & CVf_CLONE)
	149	#define CvCLONE_on(cv) (CvFLAGS(cv) \|= CVf_CLONE)
	150	#define CvCLONE_off(cv) (CvFLAGS(cv) &= ~CVf_CLONE)
	151
	152	#define CvCLONED(cv) (CvFLAGS(cv) & CVf_CLONED)
	153	#define CvCLONED_on(cv) (CvFLAGS(cv) \|= CVf_CLONED)
	154	#define CvCLONED_off(cv) (CvFLAGS(cv) &= ~CVf_CLONED)
	155
	156	#define CvANON(cv) (CvFLAGS(cv) & CVf_ANON)
	157	#define CvANON_on(cv) (CvFLAGS(cv) \|= CVf_ANON)
	158	#define CvANON_off(cv) (CvFLAGS(cv) &= ~CVf_ANON)
79072805	159
07055b4c	160	#define CvUNIQUE(cv) (CvFLAGS(cv) & CVf_UNIQUE)
	161	#define CvUNIQUE_on(cv) (CvFLAGS(cv) \|= CVf_UNIQUE)
	162	#define CvUNIQUE_off(cv) (CvFLAGS(cv) &= ~CVf_UNIQUE)
8ebc5c01	163
	164	#define CvNODEBUG(cv) (CvFLAGS(cv) & CVf_NODEBUG)
	165	#define CvNODEBUG_on(cv) (CvFLAGS(cv) \|= CVf_NODEBUG)
	166	#define CvNODEBUG_off(cv) (CvFLAGS(cv) &= ~CVf_NODEBUG)
77a005ab	167
	168	#define CvMETHOD(cv) (CvFLAGS(cv) & CVf_METHOD)
	169	#define CvMETHOD_on(cv) (CvFLAGS(cv) \|= CVf_METHOD)
	170	#define CvMETHOD_off(cv) (CvFLAGS(cv) &= ~CVf_METHOD)
	171
	172	#define CvLOCKED(cv) (CvFLAGS(cv) & CVf_LOCKED)
	173	#define CvLOCKED_on(cv) (CvFLAGS(cv) \|= CVf_LOCKED)
	174	#define CvLOCKED_off(cv) (CvFLAGS(cv) &= ~CVf_LOCKED)
1aff0e91	175
cd06dffe	176	#define CvLVALUE(cv) (CvFLAGS(cv) & CVf_LVALUE)
	177	#define CvLVALUE_on(cv) (CvFLAGS(cv) \|= CVf_LVALUE)
	178	#define CvLVALUE_off(cv) (CvFLAGS(cv) &= ~CVf_LVALUE)
	179
06492da6	180	#define CvASSERTION(cv) (CvFLAGS(cv) & CVf_ASSERTION)
	181	#define CvASSERTION_on(cv) (CvFLAGS(cv) \|= CVf_ASSERTION)
	182	#define CvASSERTION_off(cv) (CvFLAGS(cv) &= ~CVf_ASSERTION)
	183
1aff0e91	184	#define CvEVAL(cv) (CvUNIQUE(cv) && !SvFAKE(cv))
	185	#define CvEVAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_off(cv))
	186	#define CvEVAL_off(cv) CvUNIQUE_off(cv)
	187
bec31f9a	188	/* BEGIN\|CHECK\|INIT\|END */
1aff0e91	189	#define CvSPECIAL(cv) (CvUNIQUE(cv) && SvFAKE(cv))
	190	#define CvSPECIAL_on(cv) (CvUNIQUE_on(cv),SvFAKE_on(cv))
	191	#define CvSPECIAL_off(cv) (CvUNIQUE_off(cv),SvFAKE_off(cv))
beab0874	192
	193	#define CvCONST(cv) (CvFLAGS(cv) & CVf_CONST)
	194	#define CvCONST_on(cv) (CvFLAGS(cv) \|= CVf_CONST)
	195	#define CvCONST_off(cv) (CvFLAGS(cv) &= ~CVf_CONST)
a4f1a029	196
7dafbf52	197	#define CvWEAKOUTSIDE(cv) (CvFLAGS(cv) & CVf_WEAKOUTSIDE)
	198	#define CvWEAKOUTSIDE_on(cv) (CvFLAGS(cv) \|= CVf_WEAKOUTSIDE)
	199	#define CvWEAKOUTSIDE_off(cv) (CvFLAGS(cv) &= ~CVf_WEAKOUTSIDE)
	200
d04ba589	201	#define CvISXSUB(cv) (CvFLAGS(cv) & CVf_ISXSUB)
	202	#define CvISXSUB_on(cv) (CvFLAGS(cv) \|= CVf_ISXSUB)
	203	#define CvISXSUB_off(cv) (CvFLAGS(cv) &= ~CVf_ISXSUB)
	204
7dafbf52	205	/*
	206	=head1 CV reference counts and CvOUTSIDE
	207
	208	=for apidoc m\|bool\|CvWEAKOUTSIDE\|CV *cv
	209
	210	Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
	211	CV (if any). Because pointers to anonymous sub prototypes are
	212	stored in C<&> pad slots, it is a possible to get a circular reference,
	213	with the parent pointing to the child and vice-versa. To avoid the
	214	ensuing memory leak, we do not increment the reference count of the CV
	215	pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
	216	has a C<&> pad slot pointing back to us. In this case, we set the
	217	C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
	218	circumstances we should decrement the refcount of the parent when freeing
	219	the child.
	220
eeb8d49e	221	There is a further complication with non-closure anonymous subs (i.e. those
7dafbf52	222	that do not refer to any lexicals outside that sub). In this case, the
	223	anonymous prototype is shared rather than being cloned. This has the
	224	consequence that the parent may be freed while there are still active
	225	children, eg
	226
	227	BEGIN { $a = sub { eval '$x' } }
	228
	229	In this case, the BEGIN is freed immediately after execution since there
	230	are no active references to it: the anon sub prototype has
	231	C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
	232	CV, so it doesn't contribute to BEGIN's refcount either. When $a is
	233	executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
	234	and the freed BEGIN is accessed.
	235
	236	To avoid this, whenever a CV and its associated pad is freed, any
	237	C<&> entries in the pad are explicitly removed from the pad, and if the
	238	refcount of the pointed-to anon sub is still positive, then that
	239	child's C<CvOUTSIDE> is set to point to its grandparent. This will only
	240	occur in the single specific case of a non-closure anon prototype
	241	having one or more active references (such as C<$a> above).
	242
	243	One other thing to consider is that a CV may be merely undefined
	244	rather than freed, eg C<undef &foo>. In this case, its refcount may
	245	not have reached zero, but we still delete its pad and its C<CvROOT> etc.
	246	Since various children may still have their C<CvOUTSIDE> pointing at this
	247	undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
	248	the chain of lexical scopes is unbroken. For example, the following
	249	should print 123:
	250
	251	my $x = 123;
	252	sub tmp { sub { eval '$x' } }
	253	my $a = tmp();
	254	undef &tmp;
	255	print $a->();
	256
	257	=cut
	258	*/
102d3b8a	259
	260	/*
	261	* Local variables:
	262	* c-indentation-style: bsd
	263	* c-basic-offset: 4
	264	* indent-tabs-mode: t
	265	* End:
	266	*
	267	* ex: set ts=8 sts=4 sw=4 noet:
	268	*/