[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). */
#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)

/* Flags for newXS_flags  */
#define XS_DYNAMIC_FILENAME	0x01	/* The filename isn't static  */

/*
=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,
1108974d	139	* require, eval). */
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 AD	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 CS	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 MB	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 GS	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 SF	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 GS	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 GS	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 JT	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 DM	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 NC	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
77004dee NC	205	/* Flags for newXS_flags */
	206	#define XS_DYNAMIC_FILENAME 0x01 /* The filename isn't static */
	207
7dafbf52 DM	208	/*
	209	=head1 CV reference counts and CvOUTSIDE
	210
	211	=for apidoc m\|bool\|CvWEAKOUTSIDE\|CV *cv
	212
	213	Each CV has a pointer, C<CvOUTSIDE()>, to its lexically enclosing
	214	CV (if any). Because pointers to anonymous sub prototypes are
	215	stored in C<&> pad slots, it is a possible to get a circular reference,
	216	with the parent pointing to the child and vice-versa. To avoid the
	217	ensuing memory leak, we do not increment the reference count of the CV
	218	pointed to by C<CvOUTSIDE> in the I<one specific instance> that the parent
	219	has a C<&> pad slot pointing back to us. In this case, we set the
	220	C<CvWEAKOUTSIDE> flag in the child. This allows us to determine under what
	221	circumstances we should decrement the refcount of the parent when freeing
	222	the child.
	223
eeb8d49e	224	There is a further complication with non-closure anonymous subs (i.e. those
7dafbf52 DM	225	that do not refer to any lexicals outside that sub). In this case, the
	226	anonymous prototype is shared rather than being cloned. This has the
	227	consequence that the parent may be freed while there are still active
	228	children, eg
	229
	230	BEGIN { $a = sub { eval '$x' } }
	231
	232	In this case, the BEGIN is freed immediately after execution since there
	233	are no active references to it: the anon sub prototype has
	234	C<CvWEAKOUTSIDE> set since it's not a closure, and $a points to the same
	235	CV, so it doesn't contribute to BEGIN's refcount either. When $a is
	236	executed, the C<eval '$x'> causes the chain of C<CvOUTSIDE>s to be followed,
	237	and the freed BEGIN is accessed.
	238
	239	To avoid this, whenever a CV and its associated pad is freed, any
	240	C<&> entries in the pad are explicitly removed from the pad, and if the
	241	refcount of the pointed-to anon sub is still positive, then that
	242	child's C<CvOUTSIDE> is set to point to its grandparent. This will only
	243	occur in the single specific case of a non-closure anon prototype
	244	having one or more active references (such as C<$a> above).
	245
	246	One other thing to consider is that a CV may be merely undefined
	247	rather than freed, eg C<undef &foo>. In this case, its refcount may
	248	not have reached zero, but we still delete its pad and its C<CvROOT> etc.
	249	Since various children may still have their C<CvOUTSIDE> pointing at this
	250	undefined CV, we keep its own C<CvOUTSIDE> for the time being, so that
	251	the chain of lexical scopes is unbroken. For example, the following
	252	should print 123:
	253
	254	my $x = 123;
	255	sub tmp { sub { eval '$x' } }
	256	my $a = tmp();
	257	undef &tmp;
	258	print $a->();
	259
	260	=cut
	261	*/
102d3b8a NC	262
	263	/*
	264	* Local variables:
	265	* c-indentation-style: bsd
	266	* c-basic-offset: 4
	267	* indent-tabs-mode: t
	268	* End:
	269	*
	270	* ex: set ts=8 sts=4 sw=4 noet:
	271	*/