Devel::CallChecker(3pmUser Contributed Perl DocumentatiDevel::CallChecker(3pm)NAMEDevel::CallChecker - custom op checking attached to subroutines
SYNOPSIS
# to generate header prior to XS compilation
perl -MDevel::CallChecker=callchecker0_h \
-e 'print callchecker0_h' > callchecker0.h
# in Perl part of module
use Devel::CallChecker;
/* in XS */
#include "callchecker0.h"
cv_get_call_checker(cv, &ckfun, &ckobj);
static OP *my_ckfun(pTHX_ OP *o, GV *namegv, SV *ckobj);
cv_set_call_checker(cv, my_ckfun, ckobj);
DESCRIPTION
This module makes some new features of the Perl 5.14.0 C API available
to XS modules running on older versions of Perl. The features are
centred around the function "cv_set_call_checker", which allows XS code
to attach a magical annotation to a Perl subroutine, resulting in
resolvable calls to that subroutine being mutated at compile time by
arbitrary C code. This module makes "cv_set_call_checker" and several
supporting functions available. (It is possible to achieve the effect
of "cv_set_call_checker" from XS code on much earlier Perl versions,
but it is painful to achieve without the centralised facility.)
This module provides the implementation of the functions at runtime (on
Perls where they are not provided by the core). It also, at compile
time, supplies the C header file and link library which provide access
to the functions. In normal use, "callchecker0_h" and
"callchecker_linkable" should be called at build time (not authoring
time) for the module that wishes to use the C functions.
CONSTANTS
callchecker0_h
Content of a C header file, intended to be named
""callchecker0.h"". It is to be included in XS code, and "perl.h"
must be included first. When the XS module is loaded at runtime,
the "Devel::CallChecker" module must be loaded first. This will
result in the Perl API functions "rv2cv_op_cv",
"ck_entersub_args_list", "ck_entersub_args_proto",
"ck_entersub_args_proto_or_list", "cv_get_call_checker", and
"cv_set_call_checker", as defined below and in the Perl 5.14.0 API,
being available to the XS code.
callchecker_linkable
List of names of files that must be used as additional objects when
linking an XS module that uses the C functions supplied by this
module. This list will be empty on many platforms.
C FUNCTIONS
rv2cv_op_cv
Examines an op, which is expected to identify a subroutine at
runtime, and attempts to determine at compile time which subroutine
it identifies. This is normally used during Perl compilation to
determine whether a prototype can be applied to a function call.
cvop is the op being considered, normally an "rv2cv" op. A pointer
to the identified subroutine is returned, if it could be determined
statically, and a null pointer is returned if it was not possible
to determine statically.
Whether the subroutine is statically identifiable is determined in
accordance with the prevailing standards of the Perl version being
used. The same criteria are used that the core uses to determine
whether to apply a prototype to a subroutine call. From version
5.11.2 onwards, the subroutine can be determined if the RV that the
"rv2cv" is to operate on is provided by a suitable "gv" or "const"
op. Prior to 5.11.2, only a "gv" op will do. A "gv" op is
suitable if the GV's CV slot is populated. A "const" op is
suitable if the constant value must be an RV pointing to a CV.
Details of this process may change in future versions of Perl.
If the "rv2cv" op has the "OPpENTERSUB_AMPER" flag set then no
attempt is made to identify the subroutine statically: this flag is
used to suppress compile-time magic on a subroutine call, forcing
it to use default runtime behaviour.
If flags has the bit "RV2CVOPCV_MARK_EARLY" set, then the handling
of a GV reference is modified. If a GV was examined and its CV
slot was found to be empty, then the "gv" op has the "OPpEARLY_CV"
flag set. If the op is not optimised away, and the CV slot is
later populated with a subroutine having a prototype, that flag
eventually triggers the warning "called too early to check
prototype".
If flags has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead
of returning a pointer to the subroutine it returns a pointer to
the GV giving the most appropriate name for the subroutine in this
context. Normally this is just the "CvGV" of the subroutine, but
for an anonymous ("CvANON") subroutine that is referenced through a
GV it will be the referencing GV. The resulting "GV*" is cast to
"CV*" to be returned. A null pointer is returned as usual if there
is no statically-determinable subroutine.
CV *rv2cv_op_cv(OP *cvop, U32 flags)
cv_get_call_checker
Retrieves the function that will be used to fix up a call to cv.
Specifically, the function is applied to an "entersub" op tree for
a subroutine call, not marked with "&", where the callee can be
identified at compile time as cv.
The C-level function pointer is returned in *ckfun_p, and an SV
argument for it is returned in *ckobj_p. The function is intended
to be called in this manner:
entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));
In this call, entersubop is a pointer to the "entersub" op, which
may be replaced by the check function, and namegv is a GV supplying
the name that should be used by the check function to refer to the
callee of the "entersub" op if it needs to emit any diagnostics.
It is permitted to apply the check function in non-standard
situations, such as to a call to a different subroutine or to a
method call.
By default, the function is Perl_ck_entersub_args_proto_or_list,
and the SV parameter is cv itself. This implements standard
prototype processing. It can be changed, for a particular
subroutine, by "cv_set_call_checker".
void cv_get_call_checker(CV *cv,
Perl_call_checker *ckfun_p, SV **ckobj_p)
cv_set_call_checker
Sets the function that will be used to fix up a call to cv.
Specifically, the function is applied to an "entersub" op tree for
a subroutine call, not marked with "&", where the callee can be
identified at compile time as cv.
The C-level function pointer is supplied in ckfun, and an SV
argument for it is supplied in ckobj. The function is intended to
be called in this manner:
entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);
In this call, entersubop is a pointer to the "entersub" op, which
may be replaced by the check function, and namegv is a GV supplying
the name that should be used by the check function to refer to the
callee of the "entersub" op if it needs to emit any diagnostics.
It is permitted to apply the check function in non-standard
situations, such as to a call to a different subroutine or to a
method call.
The current setting for a particular CV can be retrieved by
"cv_get_call_checker".
void cv_set_call_checker(CV *cv, Perl_call_checker ckfun,
SV *ckobj)
ck_entersub_args_list
Performs the default fixup of the arguments part of an "entersub"
op tree. This consists of applying list context to each of the
argument ops. This is the standard treatment used on a call marked
with "&", or a method call, or a call through a subroutine
reference, or any other call where the callee can't be identified
at compile time, or a call where the callee has no prototype.
OP *ck_entersub_args_list(OP *entersubop)
ck_entersub_args_proto
Performs the fixup of the arguments part of an "entersub" op tree
based on a subroutine prototype. This makes various modifications
to the argument ops, from applying context up to inserting "refgen"
ops, and checking the number and syntactic types of arguments, as
directed by the prototype. This is the standard treatment used on
a subroutine call, not marked with "&", where the callee can be
identified at compile time and has a prototype.
protosv supplies the subroutine prototype to be applied to the
call. It may be a normal defined scalar, of which the string value
will be used. Alternatively, for convenience, it may be a
subroutine object (a "CV*" that has been cast to "SV*") which has a
prototype. The prototype supplied, in whichever form, does not
need to match the actual callee referenced by the op tree.
If the argument ops disagree with the prototype, for example by
having an unacceptable number of arguments, a valid op tree is
returned anyway. The error is reflected in the parser state,
normally resulting in a single exception at the top level of
parsing which covers all the compilation errors that occurred. In
the error message, the callee is referred to by the name defined by
the namegv parameter.
OP *ck_entersub_args_proto(OP *entersubop, GV *namegv,
SV *protosv)
ck_entersub_args_proto_or_list
Performs the fixup of the arguments part of an "entersub" op tree
either based on a subroutine prototype or using default list-
context processing. This is the standard treatment used on a
subroutine call, not marked with "&", where the callee can be
identified at compile time.
protosv supplies the subroutine prototype to be applied to the
call, or indicates that there is no prototype. It may be a normal
scalar, in which case if it is defined then the string value will
be used as a prototype, and if it is undefined then there is no
prototype. Alternatively, for convenience, it may be a subroutine
object (a "CV*" that has been cast to "SV*"), of which the
prototype will be used if it has one. The prototype (or lack
thereof) supplied, in whichever form, does not need to match the
actual callee referenced by the op tree.
If the argument ops disagree with the prototype, for example by
having an unacceptable number of arguments, a valid op tree is
returned anyway. The error is reflected in the parser state,
normally resulting in a single exception at the top level of
parsing which covers all the compilation errors that occurred. In
the error message, the callee is referred to by the name defined by
the namegv parameter.
OP *ck_entersub_args_proto_or_list(OP *entersubop,
GV *namegv, SV *protosv)
SEE ALSO
B::CallChecker, Devel::CallParser, "cv_set_call_checker" in perlapi
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2011, 2012, 2013, 2015 Andrew Main (Zefram)
<zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.26.0 2017-07-22 Devel::CallChecker(3pm)
