perl-compiler/ramblings/magic

magic cases might need to be treated specially and testcases are quite hard to produce.


sv_magic()
----------
av.c
av_store()
	Storing a non-undef element into an SMAGICAL array, av,
	assigns the equivalent lowercase form of magic (of the first
	MAGIC in the chain) to the value (with obj = av, name = 0 and
	namlen = array index).

gv.c
gv_init()
	Initialising gv assigns '*' magic to it with obj = gv, name =
	GvNAME and namlen = GvNAMELEN.
gv_fetchpv()
	@ISA gets 'I' magic with obj = gv, zero name and namlen.
	%OVERLOAD gets 'A' magic with obj = gv, zero name and namlen.
	$1 to $9, $&, $`, $', $+ get '\0' magic with obj = gv,
	name = GvNAME and namlen = len ( = 1 presumably).
Gv_AMupdate()
	Stashes for overload magic seem to get 'c' magic with obj = 0,
	name = &amt and namlen = sizeof(amt).
hv_magic(hv, gv, how)
	Gives magic how to hv with obj = gv and zero name and namlen.

mg.c
mg_copy(sv, nsv, key, klen)
	Traverses the magic chain of sv. Upper case forms of magic
	(only) are copied across to nsv, preserving obj but using
	name = key and namlen = klen.
magic_setpos()
	LvTARG of a PVLV gets 'g' magic with obj = name = 0 and namlen = pos.

op.c
mod()
	PVLV operators give magic to their targs with
	obj = name = namlen = 0. OP_POS gives '.', OP_VEC gives 'v'
	and OP_SUBSTR gives 'x'.

perl.c
magicname(sym, name, namlen)
	Fetches/creates a GV with name sym and gives it '\0' magic
	with obj = gv, name and namlen as passed.
init_postdump_symbols()
	Elements of the environment get given SVs with 'e' magic.
	obj = sv and name and namlen point to the actual string
	within env.

pp.c
pp_av2arylen()
	$#foo gives '#' magic to the new SV with obj = av and
	name = namlen = 0.
pp_study()
	SV gets 'g' magic with obj = name = namlen = 0.
pp_substr()
	PVLV gets 'x' magic with obj = name = namlen = 0.
pp_vec()
	PVLV gets 'x' magic with obj = name = namlen = 0.

pp_hot.c
pp_match()
	m//g gets 'g' magic with obj = name = namlen = 0.

pp_sys.c
pp_tie()
	sv gets magic with obj = sv and name = namlen = 0.
	If an HV or an AV, it gets 'P' magic, otherwise 'q' magic.
pp_dbmopen()
	'P' magic for the HV just as with pp_tie().
pp_sysread()
	If tainting, the buffer SV gets 't' magic with
	obj = name = namlen = 0.

sv.c
ref loops:
        For certain magics the sv == obj - a "magic reference loop":
        arylen, symtab, tiedscalar, .... There the obj refcount is 
        not incremented.
sv_setsv()
	Doing sv_setsv(dstr, gv) gives '*' magic to dstr with
	obj = dstr, name = GvNAME, namlen = GvNAMELEN.
sv_setsv_flags()
        Set vstring on SvVSTRING_mg (RMAGIC)
sv_rvweaken()
	tiedscalar weakens the RV obj to the PVIO. Sets a backref magic 
	to the referred SV.


util.c
fbm_compile()
	The PVBM gets 'B' magic with obj = name = namlen = 0 and SvVALID
	is set to indicate that the Boyer-Moore table is valid.
	magic_setbm() just clears the SvVALID flag.

hv_magic()
----------

gv.c
gv_fetchfile()
	With perldb, the HV of a gvfile gv gets 'L' magic with obj = gv.
gv_fetchpv()
	%SIG gets 'S' magic with obj = siggv.
init_postdump_symbols()
	%ENV gets 'E' magic with obj = envgv.