# New Ticket Created by Jerry Gay
# Please include the string: [perl #43757]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=43757 >
i made some small local mods while trying to debug a segfault during
'make test' for languages/perl6. the segfault occurs when running
t/01-sanity/07-range.t.
below is my patch. there's two changes in here, one for debugging, the
other for better variable naming. since this patch causes a different
segfault, i haven't separated the content of these two patches, as i'd
like to nail this *new* segfault quickly so i can go back to *the
other one*.
---
Index: src/inter_call.c
===================================================================
--- src/inter_call.c (revision 19728)
+++ src/inter_call.c (working copy)
@@ -23,6 +23,7 @@
#include <assert.h>
#include "parrot/parrot.h"
#include "parrot/oplib/ops.h"
+#include "parrot/interpreter.h"
#include "inter_call.str"
/* HEADERIZER HFILE: include/parrot/inter_call.h */
@@ -325,27 +326,27 @@
static void
-next_arg_sig(call_state_item *st /*NN*/)
+next_arg_sig(call_state_item *sti /*NN*/)
{
- switch (st->mode & CALL_S_D_MASK) {
+ switch (sti->mode & CALL_S_D_MASK) {
case CALL_STATE_OP:
- st->sig = SIG_ITEM(st->u.op.signature, st->i);
+ sti->sig = SIG_ITEM(sti->u.op.signature, sti->i);
break;
case CALL_STATE_SIG:
- switch (st->u.sig.sig[st->i]) {
+ switch (sti->u.sig.sig[sti->i]) {
case 'I':
- st->sig = PARROT_ARG_INTVAL; break;
+ sti->sig = PARROT_ARG_INTVAL; break;
case 'N':
- st->sig = PARROT_ARG_FLOATVAL; break;
+ sti->sig = PARROT_ARG_FLOATVAL; break;
case 'S':
- st->sig = PARROT_ARG_STRING; break;
+ sti->sig = PARROT_ARG_STRING; break;
case 'O':
case 'P':
- st->sig = PARROT_ARG_PMC; break;
+ sti->sig = PARROT_ARG_PMC; break;
case '@':
- st->sig = PARROT_ARG_PMC | PARROT_ARG_SLURPY_ARRAY; break;
+ sti->sig = PARROT_ARG_PMC | PARROT_ARG_SLURPY_ARRAY; break;
case 'F':
- st->sig = PARROT_ARG_PMC | PARROT_ARG_FLATTEN; break;
+ sti->sig = PARROT_ARG_PMC | PARROT_ARG_FLATTEN; break;
}
break;
}
@@ -641,7 +642,8 @@
{
PMC *key = UVal_pmc(st->val);
- if (key && key->vtable->base_type == enum_class_Key) {
+/* printf("PMC_IS_NULL(key) = %d\n", PMC_IS_NULL(key)); */
+ if (!PMC_IS_NULL(key) && key->vtable && key->vtable->base_type == enum_clas
s_Key) {
for (; key; key=key_next(interp, key)) {
/* register keys have to be cloned */
if (PObj_get_FLAGS(key) & KEY_register_FLAG) {
---
as i mentioned, this causes another segfault--one when generating the
tree grammar for compilers.
c:\usr\local\parrot\trunk\compilers\past-pm>..\..\parrot
..\..\compilers\tge\tgc.pir --output
=POST\Grammar_gen.pir POST\Grammar.tg
here's the backtrace:
---
libparrot.dll!Parrot_NameSpace_get_pointer_keyed(parrot_interp_t *
interp=0x03ae2d80, PMC * pmc=0x03a17708, PMC * key=0x03c7b590) Line
342 + 0x6 bytes C
libparrot.dll!fail_if_exist(parrot_interp_t * interp=0x03ae2d80, PMC
* name=0x03c7b590) Line 258 + 0x1a bytes C
libparrot.dll!Parrot_new_class(parrot_interp_t * interp=0x03ae2d80,
PMC * _class=0x03ccced8, PMC * name=0x03c7b590) Line 582 + 0xd
bytes C
libparrot.dll!Parrot_ParrotClass_init_pmc(parrot_interp_t *
interp=0x03ae2d80, PMC * pmc=0x03ccced8, PMC * name=0x03c7b590) Line
82 + 0x11 bytes C
libparrot.dll!pmc_new_init(parrot_interp_t * interp=0x03ae2d80, long
base_type=47, PMC * init=0x03c7b590) Line 318 + 0x1a bytes C
> libparrot.dll!Parrot_newclass_p_pc(long * cur_opcode=0x039cf738,
parrot_interp_t * interp=0x03ae2d80) Line 231 + 0x20 bytes C
libparrot.dll!runops_slow_core(parrot_interp_t * interp=0x03ae2d80,
long * pc=0x039cf738) Line 184 + 0x18 bytes C
libparrot.dll!runops_int(parrot_interp_t * interp=0x03ae2d80,
unsigned int offset=0) Line 787 + 0xb bytes C
libparrot.dll!runops(parrot_interp_t * interp=0x03ae2d80, unsigned
int offs=0) Line 95 + 0xd bytes C
libparrot.dll!runops_args(parrot_interp_t * interp=0x03ae2d80, PMC *
sub=0x03ccd1b8, PMC * obj=0x03a1be98, parrot_string_t *
meth=0x00000000, const char * sig=0x102a06b8, char * ap=0x0017fb8c)
Line 210 + 0xd bytes C
libparrot.dll!Parrot_runops_fromc_args(parrot_interp_t *
interp=0x03ae2d80, PMC * sub=0x03ccd1b8, const char * sig=0x102a06b8,
...) Line 287 + 0x1d bytes C
libparrot.dll!run_sub(parrot_interp_t * interp=0x03ae2d80, PMC *
sub_pmc=0x03ccd1b8) Line 375 + 0x12 bytes C
libparrot.dll!do_1_sub_pragma(parrot_interp_t * interp=0x03ae2d80,
PMC * sub_pmc=0x03ccd1b8, int action=2) Line 434 + 0xd bytes C
libparrot.dll!do_sub_pragmas(parrot_interp_t * interp=0x03ae2d80,
PackFile_ByteCode * self=0x039cf470, int action=2, PMC *
eval_pmc=0x00000000) Line 566 + 0x11 bytes C
libparrot.dll!PackFile_append_pbc(parrot_interp_t *
interp=0x03ae2d80, const char * filename=0x03c1a720) Line 3250 + 0x17
bytes C
libparrot.dll!Parrot_load_bytecode(parrot_interp_t *
interp=0x03ae2d80, parrot_string_t * file_str=0x03bc0bb0) Line 3303 +
0xd bytes C
libparrot.dll!Parrot_load_bytecode_sc(long * cur_opcode=0x03c04c88,
parrot_interp_t * interp=0x03ae2d80) Line 149 + 0x1e bytes C
libparrot.dll!runops_slow_core(parrot_interp_t * interp=0x03ae2d80,
long * pc=0x03c04c88) Line 184 + 0x18 bytes C
libparrot.dll!runops_int(parrot_interp_t * interp=0x03ae2d80,
unsigned int offset=0) Line 787 + 0xb bytes C
libparrot.dll!runops(parrot_interp_t * interp=0x03ae2d80, unsigned
int offs=0) Line 95 + 0xd bytes C
libparrot.dll!runops_args(parrot_interp_t * interp=0x03ae2d80, PMC *
sub=0x03be3c20, PMC * obj=0x03a1be98, parrot_string_t *
meth=0x00000000, const char * sig=0x102a06b8, char * ap=0x0017fd18)
Line 210 + 0xd bytes C
libparrot.dll!Parrot_runops_fromc_args(parrot_interp_t *
interp=0x03ae2d80, PMC * sub=0x03be3c20, const char * sig=0x102a06b8,
...) Line 287 + 0x1d bytes C
libparrot.dll!run_sub(parrot_interp_t * interp=0x03ae2d80, PMC *
sub_pmc=0x03be3c20) Line 375 + 0x12 bytes C
libparrot.dll!do_1_sub_pragma(parrot_interp_t * interp=0x03ae2d80,
PMC * sub_pmc=0x03be3c20, int action=2) Line 434 + 0xd bytes C
libparrot.dll!do_sub_pragmas(parrot_interp_t * interp=0x03ae2d80,
PackFile_ByteCode * self=0x03c049f0, int action=2, PMC *
eval_pmc=0x00000000) Line 566 + 0x11 bytes C
libparrot.dll!PackFile_append_pbc(parrot_interp_t *
interp=0x03ae2d80, const char * filename=0x03c19588) Line 3250 + 0x17
bytes C
libparrot.dll!Parrot_load_bytecode(parrot_interp_t *
interp=0x03ae2d80, parrot_string_t * file_str=0x03bc0e30) Line 3303 +
0xd bytes C
libparrot.dll!Parrot_load_bytecode_sc(long * cur_opcode=0x03c19e4c,
parrot_interp_t * interp=0x03ae2d80) Line 149 + 0x1e bytes C
libparrot.dll!runops_slow_core(parrot_interp_t * interp=0x03ae2d80,
long * pc=0x03c19e4c) Line 184 + 0x18 bytes C
libparrot.dll!runops_int(parrot_interp_t * interp=0x03ae2d80,
unsigned int offset=3) Line 787 + 0xb bytes C
libparrot.dll!runops(parrot_interp_t * interp=0x03ae2d80, unsigned
int offs=3) Line 95 + 0xd bytes C
libparrot.dll!runops_args(parrot_interp_t * interp=0x03ae2d80, PMC *
sub=0x03be3ea0, PMC * obj=0x03a1be98, parrot_string_t *
meth=0x00000000, const char * sig=0x102a2d7c, char * ap=0x0017fea4)
Line 210 + 0xd bytes C
libparrot.dll!Parrot_runops_fromc_args(parrot_interp_t *
interp=0x03ae2d80, PMC * sub=0x03be3ea0, const char * sig=0x102a2d7c,
...) Line 287 + 0x1d bytes C
libparrot.dll!Parrot_runcode(parrot_interp_t * interp=0x03ae2d80,
int argc=3, char * * argv=0x03ae2ce4) Line 783 + 0x16 bytes C
libparrot.dll!imcc_run_pbc(parrot_interp_t * interp=0x03ae2d80, int
obj_file=0, const char * output_file=0x00000000, int argc=3, char * *
argv=0x03ae2ce4) Line 607 + 0x11 bytes C
libparrot.dll!imcc_run(parrot_interp_t * interp=0x03ae2d80, const
char * sourcefile=0x03ae2d19, int argc=3, char * * argv=0x03ae2ce4)
Line 808 + 0x19 bytes C
parrot.exe!main(int argc=3, char * * argv=0x03ae2ce4) Line 62 + 0x15
bytes C
parrot.exe!__tmainCRTStartup() Line 586 + 0x17 bytes C
kernel32.dll!772119f1()
[Frames below may be incorrect and/or missing, no symbols loaded for
kernel32.dll]
ntdll.dll!77c1d109()
---
the code bombs out at src/pmc/namespace.pmc:342
if (key->vtable->base_type == enum_class_String) {
because 'key' is not a valid pmc, therefore ->vtable is not valid
address. *boom*
'Parrot_NameSpace_get_pointer_keyed' has documentation that says:
=item C<void* get_pointer_keyed(PMC *key)>
Return the given namespace item or PMCNULL. If the named item is either
a NameSpace or a var, the var is returned.
TOTAL KLUDGE. ON THE CHOPPING BLOCK.
=cut
yuck. please, let's do something about that--and soon. but, the key
passed into this function is invalid, so it's somewhere up the call
chain. let's dig deeper....
tracing back through the call chain, i see this invalid pmc is passed
through a number of calls, untouched. the pmc is created in
Parrot_newclass_p_pc, which is the 'newclass' op in
src/ops/object.ops.
since the backtrace points directly to the .ops file, i can't see
what's going on in the .c code without using an external editor. so i
fire up 'gvim -t Parrot_newclass_p_pc' (andy++ for that time-saving
hack) which brings me directly to the function (you have run 'make
tags', haven't you?) here's what i find:
opcode_t *
Parrot_newclass_p_pc (opcode_t *cur_opcode, Interp *interp) {
#line 231 "src\\ops\\object.ops"
PREG(1) = pmc_new_init(interp, enum_class_ParrotClass, CONST(2)->u.key);
return (opcode_t *)cur_opcode + 3;
}
unrolling several nested macros, PREG(1) converts to:
(&(interp)->ctx)->bp_ps.regs_p[-1L-(cur_opcode[1])]
looking inside, i can see this is a Null PMC.
(&(interp)->ctx)->bp_ps.regs_p[-1L-(cur_opcode[1])]->vtable->isa_str->strstart
0x102a4c54
"Null" char *
doing the same for CONST(2)->u.key:
interp->ctx.state->constants[cur_opcode[2]]
and again looking inside, i see this pmc constant is a Key for "TGE::Rule".
interp->ctx.state->constants[cur_opcode[2]]->u.string->strstart
0x039eacac
"TGE::Rule" char *
now we're getting somewhere!
using every parrot developer's favorite search tool, ack, i find all
references to 'TGE::Rule' in the compilers directory:
ack --all "TGE::Rule" compilers
yields:
Binary file compilers\tge\TGE\Grammar.pbc matches
compilers\tge\TGE\Grammar.pir
31:of TGE::Rule objects, which are the semantics defined by the grammar.
56: rule = new 'TGE::Rule'
Binary file compilers\tge\TGE\Rule.pbc matches
compilers\tge\TGE\Rule.pir
5:TGE::Rule - a single rule in the attribute grammar
13:.namespace [ "TGE::Rule" ]
20: newclass base, "TGE::Rule"
HEY! lookie there, compilers/tge/TGE/Rule.pir contains 'newclass base,
"TGE::Rule"'. that's exactly what i'm looking for. now i know where
this invalid pmc comes from. but *why* is it invalid?
AARGH! okay, this is the part where i recompile parrot after adding
some debugging code, and the segfault *moves*. ain't that grand?
it hasn't moved far, though. it still occurs during the same
command-line command. but, now it's in the 'subclass' op (which is
earlier than before.) luckily, using the structures i added to my
watch list (and adding one more) tell me it's running something like:
$P0 = subclass 'PGE::Grammar', 'TGE::Parser'
that happens to be line 5 of compilers/tge/TGE/Parser.pir (generated
by pgc.pir from Parser.pg in that same directory.)
here's the source for the subclass op:
opcode_t *
Parrot_subclass_p_pc_pc (opcode_t *cur_opcode, Interp *interp) {
#line 341 "src\\ops\\object.ops"
PMC *_class = Parrot_class_lookup_p(interp, CONST(2)->u.key);
opcode_t *next = cur_opcode + 4;
if (PMC_IS_NULL(_class)) {
STRING *name = readable_name(interp, CONST(2)->u.key);
real_exception(interp, next, NO_CLASS,
"Class '%Ss' doesn't exist", name);
}
PREG(1) = VTABLE_subclass(interp, _class, CONST(3)->u.key);
return (opcode_t *)next;
}
hey, look at that! here's what my debugger shows for the structure
known above as CONST(2)->u.key (which is equivalent to $2 in the .ops
file before ops2c.pl gets it's hands on it):
- interp->ctx.state->constants[cur_opcode[2]]->u.key
0x03b7a1e0
{obj={...} vtable=0x0000000c real_self=0x038ab1c4 ...} PMC *
+ obj {u={...} flags=397568 } pobj_t
+ vtable 0x0000000c {_namespace=??? base_type=??? whoami=???
...} _vtable *
+ real_self 0x038ab1c4 {obj={...} vtable=0x3a454754
real_self=0x7261503a ...} PMC *
+ pmc_ext 0x0000000c {data=??? _metadata=??? _synchronize=???
...} PMC_EXT *
that's an *totally* uninitialized key.
here's what i don't get: why is it expecting a key, anyway? i mean,
the op is getting two pir strings.
$P0 = subclass 'PGE::Grammar', 'TGE::Parser'
why isn't that calling subclass_p_sc_sc?
if it were:
$P0 = subclass ['PGE::Grammar'], ['TGE::Parser']
then i'd expect it to call subclass_p_pc_pc (or perhaps subclass_p_kc_kc.)
well, at this point, i can't recreate the segfault, but i still have
questions about why that particular op is being called. please, can
someone enlighten me? it's knowledge that will definitely come in
handy when debugging in the future.
~jerry
