Devel::CallChecker - custom op checking attached to subroutines
# 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);
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.
- 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.
- 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)
the B::CallChecker manpage,
the Devel::CallParser manpage,
perlapi/cv_set_call_checker
Andrew Main (Zefram) <zefram@fysh.org>
Copyright (C) 2011, 2012, 2013, 2015, 2017
Andrew Main (Zefram) <zefram@fysh.org>
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
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