1Devel::CallChecker(3) User Contributed Perl DocumentationDevel::CallChecker(3)
2
6 Devel::CallChecker - custom op checking attached to subroutines
7
9 # to generate header prior to XS compilation
10 perl -MDevel::CallChecker=callchecker0_h \
12 -e 'print callchecker0_h' > callchecker0.h
13 # in Perl part of module
15 use Devel::CallChecker;
17 /* in XS */
19 #include "callchecker0.h"
21 cv_get_call_checker(cv, &ckfun, &ckobj);
23 static OP *my_ckfun(pTHX_ OP *o, GV *namegv, SV *ckobj);
24 cv_set_call_checker(cv, my_ckfun, ckobj);
25
27 This module makes some new features of the Perl 5.14.0 C API available
28 to XS modules running on older versions of Perl. The features are
29 centred around the function "cv_set_call_checker", which allows XS code
30 to attach a magical annotation to a Perl subroutine, resulting in
31 resolvable calls to that subroutine being mutated at compile time by
32 arbitrary C code. This module makes "cv_set_call_checker" and several
33 supporting functions available. (It is possible to achieve the effect
34 of "cv_set_call_checker" from XS code on much earlier Perl versions,
35 but it is painful to achieve without the centralised facility.)
36 This module provides the implementation of the functions at runtime (on
38 Perls where they are not provided by the core). It also, at compile
39 time, supplies the C header file and link library which provide access
40 to the functions. In normal use, "callchecker0_h" and
41 "callchecker_linkable" should be called at build time (not authoring
42 time) for the module that wishes to use the C functions.
43
45 callchecker0_h
46 Content of a C header file, intended to be named
47 ""callchecker0.h"". It is to be included in XS code, and "perl.h"
48 must be included first. When the XS module is loaded at runtime,
49 the "Devel::CallChecker" module must be loaded first. This will
50 result in the Perl API functions "rv2cv_op_cv",
51 "ck_entersub_args_list", "ck_entersub_args_proto",
52 "ck_entersub_args_proto_or_list", "cv_get_call_checker", and
53 "cv_set_call_checker", as defined below and in the Perl 5.14.0 API,
54 being available to the XS code.
55 callchecker_linkable
57 List of names of files that must be used as additional objects when
58 linking an XS module that uses the C functions supplied by this
59 module. This list will be empty on many platforms.
60
62 rv2cv_op_cv
63 Examines an op, which is expected to identify a subroutine at
64 runtime, and attempts to determine at compile time which subroutine
65 it identifies. This is normally used during Perl compilation to
66 determine whether a prototype can be applied to a function call.
67 cvop is the op being considered, normally an "rv2cv" op. A pointer
68 to the identified subroutine is returned, if it could be determined
69 statically, and a null pointer is returned if it was not possible
70 to determine statically.
71 Whether the subroutine is statically identifiable is determined in
73 accordance with the prevailing standards of the Perl version being
74 used. The same criteria are used that the core uses to determine
75 whether to apply a prototype to a subroutine call. From version
76 5.11.2 onwards, the subroutine can be determined if the RV that the
77 "rv2cv" is to operate on is provided by a suitable "gv" or "const"
78 op. Prior to 5.11.2, only a "gv" op will do. A "gv" op is
79 suitable if the GV's CV slot is populated. A "const" op is
80 suitable if the constant value must be an RV pointing to a CV.
81 Details of this process may change in future versions of Perl.
82 If the "rv2cv" op has the "OPpENTERSUB_AMPER" flag set then no
84 attempt is made to identify the subroutine statically: this flag is
85 used to suppress compile-time magic on a subroutine call, forcing
86 it to use default runtime behaviour.
87 If flags has the bit "RV2CVOPCV_MARK_EARLY" set, then the handling
89 of a GV reference is modified. If a GV was examined and its CV
90 slot was found to be empty, then the "gv" op has the "OPpEARLY_CV"
91 flag set. If the op is not optimised away, and the CV slot is
92 later populated with a subroutine having a prototype, that flag
93 eventually triggers the warning "called too early to check
94 prototype".
95 If flags has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead
97 of returning a pointer to the subroutine it returns a pointer to
98 the GV giving the most appropriate name for the subroutine in this
99 context. Normally this is just the "CvGV" of the subroutine, but
100 for an anonymous ("CvANON") subroutine that is referenced through a
101 GV it will be the referencing GV. The resulting "GV*" is cast to
102 "CV*" to be returned. A null pointer is returned as usual if there
103 is no statically-determinable subroutine.
104 CV *rv2cv_op_cv(OP *cvop, U32 flags)
106 cv_get_call_checker
108 Retrieves the function that will be used to fix up a call to cv.
109 Specifically, the function is applied to an "entersub" op tree for
110 a subroutine call, not marked with "&", where the callee can be
111 identified at compile time as cv.
112 The C-level function pointer is returned in *ckfun_p, and an SV
114 argument for it is returned in *ckobj_p. The function is intended
115 to be called in this manner:
116 entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));
118 In this call, entersubop is a pointer to the "entersub" op, which
120 may be replaced by the check function, and namegv is a GV supplying
121 the name that should be used by the check function to refer to the
122 callee of the "entersub" op if it needs to emit any diagnostics.
123 It is permitted to apply the check function in non-standard
124 situations, such as to a call to a different subroutine or to a
125 method call.
126 By default, the function is Perl_ck_entersub_args_proto_or_list,
128 and the SV parameter is cv itself. This implements standard
129 prototype processing. It can be changed, for a particular
130 subroutine, by "cv_set_call_checker".
131 void cv_get_call_checker(CV *cv, Perl_call_checker *ckfun_p,
133 SV **ckobj_p)
134 cv_set_call_checker
136 Sets the function that will be used to fix up a call to cv.
137 Specifically, the function is applied to an "entersub" op tree for
138 a subroutine call, not marked with "&", where the callee can be
139 identified at compile time as cv.
140 The C-level function pointer is supplied in ckfun, and an SV
142 argument for it is supplied in ckobj. The function is intended to
143 be called in this manner:
144 entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);
146 In this call, entersubop is a pointer to the "entersub" op, which
148 may be replaced by the check function, and namegv is a GV supplying
149 the name that should be used by the check function to refer to the
150 callee of the "entersub" op if it needs to emit any diagnostics.
151 It is permitted to apply the check function in non-standard
152 situations, such as to a call to a different subroutine or to a
153 method call.
154 The current setting for a particular CV can be retrieved by
156 "cv_get_call_checker".
157 void cv_set_call_checker(CV *cv, Perl_call_checker ckfun,
159 SV *ckobj)
160 ck_entersub_args_list
162 Performs the default fixup of the arguments part of an "entersub"
163 op tree. This consists of applying list context to each of the
164 argument ops. This is the standard treatment used on a call marked
165 with "&", or a method call, or a call through a subroutine
166 reference, or any other call where the callee can't be identified
167 at compile time, or a call where the callee has no prototype.
168 OP *ck_entersub_args_list(OP *entersubop)
170 ck_entersub_args_proto
172 Performs the fixup of the arguments part of an "entersub" op tree
173 based on a subroutine prototype. This makes various modifications
174 to the argument ops, from applying context up to inserting "refgen"
175 ops, and checking the number and syntactic types of arguments, as
176 directed by the prototype. This is the standard treatment used on
177 a subroutine call, not marked with "&", where the callee can be
178 identified at compile time and has a prototype.
179 protosv supplies the subroutine prototype to be applied to the
181 call. It may be a normal defined scalar, of which the string value
182 will be used. Alternatively, for convenience, it may be a
183 subroutine object (a "CV*" that has been cast to "SV*") which has a
184 prototype. The prototype supplied, in whichever form, does not
185 need to match the actual callee referenced by the op tree.
186 If the argument ops disagree with the prototype, for example by
188 having an unacceptable number of arguments, a valid op tree is
189 returned anyway. The error is reflected in the parser state,
190 normally resulting in a single exception at the top level of
191 parsing which covers all the compilation errors that occurred. In
192 the error message, the callee is referred to by the name defined by
193 the namegv parameter.
194 OP *ck_entersub_args_proto(OP *entersubop, GV *namegv,
196 SV *protosv)
197 ck_entersub_args_proto_or_list
199 Performs the fixup of the arguments part of an "entersub" op tree
200 either based on a subroutine prototype or using default list-
201 context processing. This is the standard treatment used on a
202 subroutine call, not marked with "&", where the callee can be
203 identified at compile time.
204 protosv supplies the subroutine prototype to be applied to the
206 call, or indicates that there is no prototype. It may be a normal
207 scalar, in which case if it is defined then the string value will
208 be used as a prototype, and if it is undefined then there is no
209 prototype. Alternatively, for convenience, it may be a subroutine
210 object (a "CV*" that has been cast to "SV*"), of which the
211 prototype will be used if it has one. The prototype (or lack
212 thereof) supplied, in whichever form, does not need to match the
213 actual callee referenced by the op tree.
214 If the argument ops disagree with the prototype, for example by
216 having an unacceptable number of arguments, a valid op tree is
217 returned anyway. The error is reflected in the parser state,
218 normally resulting in a single exception at the top level of
219 parsing which covers all the compilation errors that occurred. In
220 the error message, the callee is referred to by the name defined by
221 the namegv parameter.
222 OP *ck_entersub_args_proto_or_list(OP *entersubop, GV *namegv,
224 SV *protosv)
225
227 B::CallChecker, Devel::CallParser, "cv_set_call_checker" in perlapi
228
230 Andrew Main (Zefram) <zefram@fysh.org>
231
233 Copyright (C) 2011, 2012, 2013, 2015, 2017 Andrew Main (Zefram)
234 <zefram@fysh.org>
235
237 This module is free software; you can redistribute it and/or modify it
238 under the same terms as Perl itself.
239perl v5.28.0 2018-07-14 Devel::CallChecker(3)