$VERSION "a5" doesn't quite work.
[p5sagit/p5-mst-13.2.git] / cop.h
1 /*    cop.h
2  *
3  *    Copyright (c) 1991-2001, Larry Wall
4  *
5  *    You may distribute under the terms of either the GNU General Public
6  *    License or the Artistic License, as specified in the README file.
7  *
8  */
9
10 struct cop {
11     BASEOP
12     char *      cop_label;      /* label for this construct */
13 #ifdef USE_ITHREADS
14     char *      cop_stashpv;    /* package line was compiled in */
15     char *      cop_file;       /* file name the following line # is from */
16 #else
17     HV *        cop_stash;      /* package line was compiled in */
18     GV *        cop_filegv;     /* file the following line # is from */
19 #endif
20     U32         cop_seq;        /* parse sequence number */
21     I32         cop_arybase;    /* array base this line was compiled with */
22     line_t      cop_line;       /* line # of this command */
23     SV *        cop_warnings;   /* lexical warnings bitmask */
24     SV *        cop_io;         /* lexical IO defaults */
25 };
26
27 #define Nullcop Null(COP*)
28
29 #ifdef USE_ITHREADS
30 #  define CopFILE(c)            ((c)->cop_file)
31 #  define CopFILEGV(c)          (CopFILE(c) \
32                                  ? gv_fetchfile(CopFILE(c)) : Nullgv)
33 #  define CopFILE_set(c,pv)     ((c)->cop_file = savepv(pv))
34 #  define CopFILESV(c)          (CopFILE(c) \
35                                  ? GvSV(gv_fetchfile(CopFILE(c))) : Nullsv)
36 #  define CopFILEAV(c)          (CopFILE(c) \
37                                  ? GvAV(gv_fetchfile(CopFILE(c))) : Nullav)
38 #  define CopSTASHPV(c)         ((c)->cop_stashpv)
39 #  define CopSTASHPV_set(c,pv)  ((c)->cop_stashpv = ((pv) ? savepv(pv) : Nullch))
40 #  define CopSTASH(c)           (CopSTASHPV(c) \
41                                  ? gv_stashpv(CopSTASHPV(c),GV_ADD) : Nullhv)
42 #  define CopSTASH_set(c,hv)    CopSTASHPV_set(c, (hv) ? HvNAME(hv) : Nullch)
43 #  define CopSTASH_eq(c,hv)     ((hv)                                   \
44                                  && (CopSTASHPV(c) == HvNAME(hv)        \
45                                      || (CopSTASHPV(c) && HvNAME(hv)    \
46                                          && strEQ(CopSTASHPV(c), HvNAME(hv)))))
47 #else
48 #  define CopFILEGV(c)          ((c)->cop_filegv)
49 #  define CopFILEGV_set(c,gv)   ((c)->cop_filegv = (GV*)SvREFCNT_inc(gv))
50 #  define CopFILE_set(c,pv)     CopFILEGV_set((c), gv_fetchfile(pv))
51 #  define CopFILESV(c)          (CopFILEGV(c) ? GvSV(CopFILEGV(c)) : Nullsv)
52 #  define CopFILEAV(c)          (CopFILEGV(c) ? GvAV(CopFILEGV(c)) : Nullav)
53 #  define CopFILE(c)            (CopFILESV(c) ? SvPVX(CopFILESV(c)) : Nullch)
54 #  define CopSTASH(c)           ((c)->cop_stash)
55 #  define CopSTASH_set(c,hv)    ((c)->cop_stash = (hv))
56 #  define CopSTASHPV(c)         (CopSTASH(c) ? HvNAME(CopSTASH(c)) : Nullch)
57    /* cop_stash is not refcounted */
58 #  define CopSTASHPV_set(c,pv)  CopSTASH_set((c), gv_stashpv(pv,GV_ADD))
59 #  define CopSTASH_eq(c,hv)     (CopSTASH(c) == (hv))
60 #endif /* USE_ITHREADS */
61
62 #define CopSTASH_ne(c,hv)       (!CopSTASH_eq(c,hv))
63 #define CopLINE(c)              ((c)->cop_line)
64 #define CopLINE_inc(c)          (++CopLINE(c))
65 #define CopLINE_dec(c)          (--CopLINE(c))
66 #define CopLINE_set(c,l)        (CopLINE(c) = (l))
67
68 /*
69  * Here we have some enormously heavy (or at least ponderous) wizardry.
70  */
71
72 /* subroutine context */
73 struct block_sub {
74     CV *        cv;
75     GV *        gv;
76     GV *        dfoutgv;
77 #ifndef USE_5005THREADS
78     AV *        savearray;
79 #endif /* USE_5005THREADS */
80     AV *        argarray;
81     U16         olddepth;
82     U8          hasargs;
83     U8          lval;           /* XXX merge lval and hasargs? */
84     SV **       oldcurpad;
85 };
86
87 #define PUSHSUB(cx)                                                     \
88         cx->blk_sub.cv = cv;                                            \
89         cx->blk_sub.olddepth = CvDEPTH(cv);                             \
90         cx->blk_sub.hasargs = hasargs;                                  \
91         cx->blk_sub.lval = PL_op->op_private &                          \
92                               (OPpLVAL_INTRO|OPpENTERSUB_INARGS);
93
94 #define PUSHFORMAT(cx)                                                  \
95         cx->blk_sub.cv = cv;                                            \
96         cx->blk_sub.gv = gv;                                            \
97         cx->blk_sub.hasargs = 0;                                        \
98         cx->blk_sub.dfoutgv = PL_defoutgv;                              \
99         (void)SvREFCNT_inc(cx->blk_sub.dfoutgv)
100
101 #ifdef USE_5005THREADS
102 #  define POP_SAVEARRAY() NOOP
103 #else
104 #  define POP_SAVEARRAY()                                               \
105     STMT_START {                                                        \
106         SvREFCNT_dec(GvAV(PL_defgv));                                   \
107         GvAV(PL_defgv) = cx->blk_sub.savearray;                         \
108     } STMT_END
109 #endif /* USE_5005THREADS */
110
111 /* junk in @_ spells trouble when cloning CVs and in pp_caller(), so don't
112  * leave any (a fast av_clear(ary), basically) */
113 #define CLEAR_ARGARRAY(ary) \
114     STMT_START {                                                        \
115         AvMAX(ary) += AvARRAY(ary) - AvALLOC(ary);                      \
116         SvPVX(ary) = (char*)AvALLOC(ary);                               \
117         AvFILLp(ary) = -1;                                              \
118     } STMT_END
119
120 #define POPSUB(cx,sv)                                                   \
121     STMT_START {                                                        \
122         if (cx->blk_sub.hasargs) {                                      \
123             POP_SAVEARRAY();                                            \
124             /* abandon @_ if it got reified */                          \
125             if (AvREAL(cx->blk_sub.argarray)) {                         \
126                 SSize_t fill = AvFILLp(cx->blk_sub.argarray);           \
127                 SvREFCNT_dec(cx->blk_sub.argarray);                     \
128                 cx->blk_sub.argarray = newAV();                         \
129                 av_extend(cx->blk_sub.argarray, fill);                  \
130                 AvFLAGS(cx->blk_sub.argarray) = AVf_REIFY;              \
131                 cx->blk_sub.oldcurpad[0] = (SV*)cx->blk_sub.argarray;   \
132             }                                                           \
133             else {                                                      \
134                 CLEAR_ARGARRAY(cx->blk_sub.argarray);                   \
135             }                                                           \
136         }                                                               \
137         sv = (SV*)cx->blk_sub.cv;                                       \
138         if (sv && (CvDEPTH((CV*)sv) = cx->blk_sub.olddepth))            \
139             sv = Nullsv;                                                \
140     } STMT_END
141
142 #define LEAVESUB(sv)                                                    \
143     STMT_START {                                                        \
144         if (sv)                                                         \
145             SvREFCNT_dec(sv);                                           \
146     } STMT_END
147
148 #define POPFORMAT(cx)                                                   \
149         setdefout(cx->blk_sub.dfoutgv);                                 \
150         SvREFCNT_dec(cx->blk_sub.dfoutgv);
151
152 /* eval context */
153 struct block_eval {
154     I32         old_in_eval;
155     I32         old_op_type;
156     SV *        old_namesv;
157     OP *        old_eval_root;
158     SV *        cur_text;
159     CV *        cv;
160 };
161
162 #define PUSHEVAL(cx,n,fgv)                                              \
163     STMT_START {                                                        \
164         cx->blk_eval.old_in_eval = PL_in_eval;                          \
165         cx->blk_eval.old_op_type = PL_op->op_type;                      \
166         cx->blk_eval.old_namesv = (n ? newSVpv(n,0) : Nullsv);          \
167         cx->blk_eval.old_eval_root = PL_eval_root;                      \
168         cx->blk_eval.cur_text = PL_linestr;                             \
169         cx->blk_eval.cv = Nullcv; /* set by doeval(), as applicable */  \
170     } STMT_END
171
172 #define POPEVAL(cx)                                                     \
173     STMT_START {                                                        \
174         PL_in_eval = cx->blk_eval.old_in_eval;                          \
175         optype = cx->blk_eval.old_op_type;                              \
176         PL_eval_root = cx->blk_eval.old_eval_root;                      \
177         if (cx->blk_eval.old_namesv)                                    \
178             sv_2mortal(cx->blk_eval.old_namesv);                        \
179     } STMT_END
180
181 /* loop context */
182 struct block_loop {
183     char *      label;
184     I32         resetsp;
185     OP *        redo_op;
186     OP *        next_op;
187     OP *        last_op;
188 #ifdef USE_ITHREADS
189     void *      iterdata;
190     SV **       oldcurpad;
191 #else
192     SV **       itervar;
193 #endif
194     SV *        itersave;
195     SV *        iterlval;
196     AV *        iterary;
197     IV          iterix;
198     IV          itermax;
199 };
200
201 #ifdef USE_ITHREADS
202 #  define CxITERVAR(c)                                                  \
203         ((c)->blk_loop.iterdata                                         \
204          ? (CxPADLOOP(cx)                                               \
205             ? &((c)->blk_loop.oldcurpad)[INT2PTR(PADOFFSET, (c)->blk_loop.iterdata)] \
206             : &GvSV((GV*)(c)->blk_loop.iterdata))                       \
207          : (SV**)NULL)
208 #  define CX_ITERDATA_SET(cx,idata)                                     \
209         cx->blk_loop.oldcurpad = PL_curpad;                             \
210         if ((cx->blk_loop.iterdata = (idata)))                          \
211             cx->blk_loop.itersave = SvREFCNT_inc(*CxITERVAR(cx));
212 #else
213 #  define CxITERVAR(c)          ((c)->blk_loop.itervar)
214 #  define CX_ITERDATA_SET(cx,ivar)                                      \
215         if ((cx->blk_loop.itervar = (SV**)(ivar)))                      \
216             cx->blk_loop.itersave = SvREFCNT_inc(*CxITERVAR(cx));
217 #endif
218
219 #define PUSHLOOP(cx, dat, s)                                            \
220         cx->blk_loop.label = PL_curcop->cop_label;                      \
221         cx->blk_loop.resetsp = s - PL_stack_base;                       \
222         cx->blk_loop.redo_op = cLOOP->op_redoop;                        \
223         cx->blk_loop.next_op = cLOOP->op_nextop;                        \
224         cx->blk_loop.last_op = cLOOP->op_lastop;                        \
225         cx->blk_loop.iterlval = Nullsv;                                 \
226         cx->blk_loop.iterary = Nullav;                                  \
227         cx->blk_loop.iterix = -1;                                       \
228         CX_ITERDATA_SET(cx,dat);
229
230 #define POPLOOP(cx)                                                     \
231         SvREFCNT_dec(cx->blk_loop.iterlval);                            \
232         if (CxITERVAR(cx)) {                                            \
233             SV **s_v_p = CxITERVAR(cx);                                 \
234             sv_2mortal(*s_v_p);                                         \
235             *s_v_p = cx->blk_loop.itersave;                             \
236         }                                                               \
237         if (cx->blk_loop.iterary && cx->blk_loop.iterary != PL_curstack)\
238             SvREFCNT_dec(cx->blk_loop.iterary);
239
240 /* context common to subroutines, evals and loops */
241 struct block {
242     I32         blku_oldsp;     /* stack pointer to copy stuff down to */
243     COP *       blku_oldcop;    /* old curcop pointer */
244     I32         blku_oldretsp;  /* return stack index */
245     I32         blku_oldmarksp; /* mark stack index */
246     I32         blku_oldscopesp;        /* scope stack index */
247     PMOP *      blku_oldpm;     /* values of pattern match vars */
248     U8          blku_gimme;     /* is this block running in list context? */
249
250     union {
251         struct block_sub        blku_sub;
252         struct block_eval       blku_eval;
253         struct block_loop       blku_loop;
254     } blk_u;
255 };
256 #define blk_oldsp       cx_u.cx_blk.blku_oldsp
257 #define blk_oldcop      cx_u.cx_blk.blku_oldcop
258 #define blk_oldretsp    cx_u.cx_blk.blku_oldretsp
259 #define blk_oldmarksp   cx_u.cx_blk.blku_oldmarksp
260 #define blk_oldscopesp  cx_u.cx_blk.blku_oldscopesp
261 #define blk_oldpm       cx_u.cx_blk.blku_oldpm
262 #define blk_gimme       cx_u.cx_blk.blku_gimme
263 #define blk_sub         cx_u.cx_blk.blk_u.blku_sub
264 #define blk_eval        cx_u.cx_blk.blk_u.blku_eval
265 #define blk_loop        cx_u.cx_blk.blk_u.blku_loop
266
267 /* Enter a block. */
268 #define PUSHBLOCK(cx,t,sp) CXINC, cx = &cxstack[cxstack_ix],            \
269         cx->cx_type             = t,                                    \
270         cx->blk_oldsp           = sp - PL_stack_base,                   \
271         cx->blk_oldcop          = PL_curcop,                            \
272         cx->blk_oldmarksp       = PL_markstack_ptr - PL_markstack,      \
273         cx->blk_oldscopesp      = PL_scopestack_ix,                     \
274         cx->blk_oldretsp        = PL_retstack_ix,                       \
275         cx->blk_oldpm           = PL_curpm,                             \
276         cx->blk_gimme           = gimme;                                \
277         DEBUG_l( PerlIO_printf(Perl_debug_log, "Entering block %ld, type %s\n", \
278                     (long)cxstack_ix, PL_block_type[CxTYPE(cx)]); )
279
280 /* Exit a block (RETURN and LAST). */
281 #define POPBLOCK(cx,pm) cx = &cxstack[cxstack_ix--],                    \
282         newsp            = PL_stack_base + cx->blk_oldsp,               \
283         PL_curcop        = cx->blk_oldcop,                              \
284         PL_markstack_ptr = PL_markstack + cx->blk_oldmarksp,            \
285         PL_scopestack_ix = cx->blk_oldscopesp,                          \
286         PL_retstack_ix   = cx->blk_oldretsp,                            \
287         pm               = cx->blk_oldpm,                               \
288         gimme            = cx->blk_gimme;                               \
289         DEBUG_l( PerlIO_printf(Perl_debug_log, "Leaving block %ld, type %s\n",          \
290                     (long)cxstack_ix+1,PL_block_type[CxTYPE(cx)]); )
291
292 /* Continue a block elsewhere (NEXT and REDO). */
293 #define TOPBLOCK(cx) cx  = &cxstack[cxstack_ix],                        \
294         PL_stack_sp      = PL_stack_base + cx->blk_oldsp,               \
295         PL_markstack_ptr = PL_markstack + cx->blk_oldmarksp,            \
296         PL_scopestack_ix = cx->blk_oldscopesp,                          \
297         PL_retstack_ix   = cx->blk_oldretsp,                            \
298         PL_curpm         = cx->blk_oldpm
299
300 /* substitution context */
301 struct subst {
302     I32         sbu_iters;
303     I32         sbu_maxiters;
304     I32         sbu_rflags;
305     I32         sbu_oldsave;
306     bool        sbu_once;
307     bool        sbu_rxtainted;
308     char *      sbu_orig;
309     SV *        sbu_dstr;
310     SV *        sbu_targ;
311     char *      sbu_s;
312     char *      sbu_m;
313     char *      sbu_strend;
314     void *      sbu_rxres;
315     REGEXP *    sbu_rx;
316 };
317 #define sb_iters        cx_u.cx_subst.sbu_iters
318 #define sb_maxiters     cx_u.cx_subst.sbu_maxiters
319 #define sb_rflags       cx_u.cx_subst.sbu_rflags
320 #define sb_oldsave      cx_u.cx_subst.sbu_oldsave
321 #define sb_once         cx_u.cx_subst.sbu_once
322 #define sb_rxtainted    cx_u.cx_subst.sbu_rxtainted
323 #define sb_orig         cx_u.cx_subst.sbu_orig
324 #define sb_dstr         cx_u.cx_subst.sbu_dstr
325 #define sb_targ         cx_u.cx_subst.sbu_targ
326 #define sb_s            cx_u.cx_subst.sbu_s
327 #define sb_m            cx_u.cx_subst.sbu_m
328 #define sb_strend       cx_u.cx_subst.sbu_strend
329 #define sb_rxres        cx_u.cx_subst.sbu_rxres
330 #define sb_rx           cx_u.cx_subst.sbu_rx
331
332 #define PUSHSUBST(cx) CXINC, cx = &cxstack[cxstack_ix],                 \
333         cx->sb_iters            = iters,                                \
334         cx->sb_maxiters         = maxiters,                             \
335         cx->sb_rflags           = r_flags,                              \
336         cx->sb_oldsave          = oldsave,                              \
337         cx->sb_once             = once,                                 \
338         cx->sb_rxtainted        = rxtainted,                            \
339         cx->sb_orig             = orig,                                 \
340         cx->sb_dstr             = dstr,                                 \
341         cx->sb_targ             = targ,                                 \
342         cx->sb_s                = s,                                    \
343         cx->sb_m                = m,                                    \
344         cx->sb_strend           = strend,                               \
345         cx->sb_rxres            = Null(void*),                          \
346         cx->sb_rx               = rx,                                   \
347         cx->cx_type             = CXt_SUBST;                            \
348         rxres_save(&cx->sb_rxres, rx)
349
350 #define POPSUBST(cx) cx = &cxstack[cxstack_ix--];                       \
351         rxres_free(&cx->sb_rxres)
352
353 struct context {
354     U32         cx_type;        /* what kind of context this is */
355     union {
356         struct block    cx_blk;
357         struct subst    cx_subst;
358     } cx_u;
359 };
360
361 #define CXTYPEMASK      0xff
362 #define CXt_NULL        0
363 #define CXt_SUB         1
364 #define CXt_EVAL        2
365 #define CXt_LOOP        3
366 #define CXt_SUBST       4
367 #define CXt_BLOCK       5
368 #define CXt_FORMAT      6
369
370 /* private flags for CXt_EVAL */
371 #define CXp_REAL        0x00000100      /* truly eval'', not a lookalike */
372 #define CXp_TRYBLOCK    0x00000200      /* eval{}, not eval'' or similar */
373
374 #ifdef USE_ITHREADS
375 /* private flags for CXt_LOOP */
376 #  define CXp_PADVAR    0x00000100      /* itervar lives on pad, iterdata
377                                            has pad offset; if not set,
378                                            iterdata holds GV* */
379 #  define CxPADLOOP(c)  (((c)->cx_type & (CXt_LOOP|CXp_PADVAR))         \
380                          == (CXt_LOOP|CXp_PADVAR))
381 #endif
382
383 #define CxTYPE(c)       ((c)->cx_type & CXTYPEMASK)
384 #define CxREALEVAL(c)   (((c)->cx_type & (CXt_EVAL|CXp_REAL))           \
385                          == (CXt_EVAL|CXp_REAL))
386 #define CxTRYBLOCK(c)   (((c)->cx_type & (CXt_EVAL|CXp_TRYBLOCK))       \
387                          == (CXt_EVAL|CXp_TRYBLOCK))
388
389 #define CXINC (cxstack_ix < cxstack_max ? ++cxstack_ix : (cxstack_ix = cxinc()))
390
391 /* "gimme" values */
392
393 /*
394 =for apidoc AmU||G_SCALAR
395 Used to indicate scalar context.  See C<GIMME_V>, C<GIMME>, and
396 L<perlcall>.
397
398 =for apidoc AmU||G_ARRAY
399 Used to indicate list context.  See C<GIMME_V>, C<GIMME> and
400 L<perlcall>.
401
402 =for apidoc AmU||G_VOID
403 Used to indicate void context.  See C<GIMME_V> and L<perlcall>.
404
405 =for apidoc AmU||G_DISCARD
406 Indicates that arguments returned from a callback should be discarded.  See
407 L<perlcall>.
408
409 =for apidoc AmU||G_EVAL
410
411 Used to force a Perl C<eval> wrapper around a callback.  See
412 L<perlcall>.
413
414 =for apidoc AmU||G_NOARGS
415
416 Indicates that no arguments are being sent to a callback.  See
417 L<perlcall>.
418
419 =cut
420 */
421
422 #define G_SCALAR        0
423 #define G_ARRAY         1
424 #define G_VOID          128     /* skip this bit when adding flags below */
425
426 /* extra flags for Perl_call_* routines */
427 #define G_DISCARD       2       /* Call FREETMPS. */
428 #define G_EVAL          4       /* Assume eval {} around subroutine call. */
429 #define G_NOARGS        8       /* Don't construct a @_ array. */
430 #define G_KEEPERR      16       /* Append errors to $@, don't overwrite it */
431 #define G_NODEBUG      32       /* Disable debugging at toplevel.  */
432 #define G_METHOD       64       /* Calling method. */
433
434 /* flag bits for PL_in_eval */
435 #define EVAL_NULL       0       /* not in an eval */
436 #define EVAL_INEVAL     1       /* some enclosing scope is an eval */
437 #define EVAL_WARNONLY   2       /* used by yywarn() when calling yyerror() */
438 #define EVAL_KEEPERR    4       /* set by Perl_call_sv if G_KEEPERR */
439 #define EVAL_INREQUIRE  8       /* The code is being required. */
440
441 /* Support for switching (stack and block) contexts.
442  * This ensures magic doesn't invalidate local stack and cx pointers.
443  */
444
445 #define PERLSI_UNKNOWN          -1
446 #define PERLSI_UNDEF            0
447 #define PERLSI_MAIN             1
448 #define PERLSI_MAGIC            2
449 #define PERLSI_SORT             3
450 #define PERLSI_SIGNAL           4
451 #define PERLSI_OVERLOAD         5
452 #define PERLSI_DESTROY          6
453 #define PERLSI_WARNHOOK         7
454 #define PERLSI_DIEHOOK          8
455 #define PERLSI_REQUIRE          9
456
457 struct stackinfo {
458     AV *                si_stack;       /* stack for current runlevel */
459     PERL_CONTEXT *      si_cxstack;     /* context stack for runlevel */
460     I32                 si_cxix;        /* current context index */
461     I32                 si_cxmax;       /* maximum allocated index */
462     I32                 si_type;        /* type of runlevel */
463     struct stackinfo *  si_prev;
464     struct stackinfo *  si_next;
465     I32                 si_markoff;     /* offset where markstack begins for us.
466                                          * currently used only with DEBUGGING,
467                                          * but not #ifdef-ed for bincompat */
468 };
469
470 typedef struct stackinfo PERL_SI;
471
472 #define cxstack         (PL_curstackinfo->si_cxstack)
473 #define cxstack_ix      (PL_curstackinfo->si_cxix)
474 #define cxstack_max     (PL_curstackinfo->si_cxmax)
475
476 #ifdef DEBUGGING
477 #  define       SET_MARK_OFFSET \
478     PL_curstackinfo->si_markoff = PL_markstack_ptr - PL_markstack
479 #else
480 #  define       SET_MARK_OFFSET NOOP
481 #endif
482
483 #define PUSHSTACKi(type) \
484     STMT_START {                                                        \
485         PERL_SI *next = PL_curstackinfo->si_next;                       \
486         if (!next) {                                                    \
487             next = new_stackinfo(32, 2048/sizeof(PERL_CONTEXT) - 1);    \
488             next->si_prev = PL_curstackinfo;                            \
489             PL_curstackinfo->si_next = next;                            \
490         }                                                               \
491         next->si_type = type;                                           \
492         next->si_cxix = -1;                                             \
493         AvFILLp(next->si_stack) = 0;                                    \
494         SWITCHSTACK(PL_curstack,next->si_stack);                        \
495         PL_curstackinfo = next;                                         \
496         SET_MARK_OFFSET;                                                \
497     } STMT_END
498
499 #define PUSHSTACK PUSHSTACKi(PERLSI_UNKNOWN)
500
501 /* POPSTACK works with PL_stack_sp, so it may need to be bracketed by
502  * PUTBACK/SPAGAIN to flush/refresh any local SP that may be active */
503 #define POPSTACK \
504     STMT_START {                                                        \
505         dSP;                                                            \
506         PERL_SI *prev = PL_curstackinfo->si_prev;                       \
507         if (!prev) {                                                    \
508             PerlIO_printf(Perl_error_log, "panic: POPSTACK\n");         \
509             my_exit(1);                                                 \
510         }                                                               \
511         SWITCHSTACK(PL_curstack,prev->si_stack);                        \
512         /* don't free prev here, free them all at the END{} */          \
513         PL_curstackinfo = prev;                                         \
514     } STMT_END
515
516 #define POPSTACK_TO(s) \
517     STMT_START {                                                        \
518         while (PL_curstack != s) {                                      \
519             dounwind(-1);                                               \
520             POPSTACK;                                                   \
521         }                                                               \
522     } STMT_END