Re: Any empty members in struct xpvcv AKA CV that an XSUB can use?

Father Chrysostomos wrote:
> Daniel Dragan wrote:
>> Id like to know if there is a 2nd unused memeber in struct xpvcv. I know
>> that  union xcv_start_u  that has "OP *    xcv_start;" also has the very
>> awesome "ANY    xcv_xsubany;" which is used by ParseXS and manually by
>> me in CPAN code. "union xcv_root_u;" contains the xsub's C func pointer
>> so that is occupied. What about     PADLIST *    xcv_padlist; as a 2nd
>> ununused member for XSUBs in struct xpvcv? I'd rather not resort to
>> magic to add a 2nd magic value to a CV * if I dont have to.
> 
> While that will probably work most of the time (as would xcv_outside
> I think), you would have to be careful not to run it through
> Perl_sv_dump() or the standard thread-cloning code.  Can you use
> xcv_depth or xcv_outside_seq?  Or does your code have to run
> on 64-bit?

Must be 64 bit/void * sized. What I am trying to do is stop ABI/linking 
problems, where Dynaloader loads a XS module compiled with 5.18 into a 
5.20 process, or DEBUGGING vs no DEBUGGING or DEBUG_LEAKING_SCALARS vs 
no DEBUG_LEAKING_SCALARS. On Win32 unlike ELF, there is no global symbol 
table, so Perl/Dynaloader has no way to know if Dynaloader from 5.18 
loads a XS module that links with 5.20, and both interps (5.18/5.20) 
happen to be in %PATH. To fix this, i will have a dynaloder boot xsub 
get, then pass on a magic value that only the perl image that called 
pp_entersub/dl_install_xsub (probably latter) knows, so that 
Perl_xs_apiversion_bootcheck (or its successors) can use to make sure 
this instance of Perl_xs_apiversion_bootcheck is the same one that 
pp_entersub called. For PERL_IMPLICIT_CONTEXT builds, the "magic value" 
is aTHX/my_perl, then compare to dTHX/Perl_get_context value. Since in a 
no-PERL_IMPLICIT_CONTEXT build, the XSUB gets exactly 1 argument, CV * 
cv, so the magic value for no-PERL_IMPLICIT_CONTEXT has to be in arg cv 
for Perl_xs_apiversion_bootcheck to examine. I've picked "&PL_stack_sp" 
as the magic value for no-PERL_IMPLICIT_CONTEXT.

I could use the traditional XS_ANY but I dont feel perfectly safe taking 
it away from CPAN code (non-xsubpp based XS modules, or xs modules that 
aggregate multiple .xs files/.o files/multiple boot xsubs using custom 
code to present 1 boot xsub to the shared library system, and then calls 
all the other boot xsubs in the shared library). Changing a an XSUB's C 
proto to add another arg is impossible, so without arg my_perl, the 
magic value must be in arg cv. I could also use magic, but it seems too 
heavy weight vs finding another member in the CV body struct to unionize.

Attached is latest patch, in particular I want arg v_my_perl to be a CV 
* in the future on no-PERL_IMPLICIT_CONTEXT builds, and have 
&PL_stack_sp computed in dl_install_xsub on unthreaded perl, not in the 
XS DLL, since computing it in boot XSUB is useless since &PL_stack_sp in 
boot XSUB already links to the wrong interp if there happens to be a 
mixup and the test will pass even with interp version mixup.

I dont want this callstack ending with a SEGV anymore.

	perl512.dll!Perl_safesysmalloc(unsigned int size=12)  Line 94 + 0xd
bytes	C
   	perl512.dll!Perl_sv_grow(interpreter * my_perl=0x01c45c34, sv * const
sv=0x01ee8600, unsigned int newlen=1)  Line 1562 + 0x6 bytes	C
   	perl512.dll!Perl_sv_setpvn(interpreter * my_perl=0x01c45c34, sv *
const sv=0x01ee8600, const char * const ptr=0x02031748, const unsigned
int len=0)  Line 4343 + 0x14 bytes	C
   	perl512.dll!Perl_newSVpvn_flags(interpreter * my_perl=0x01c45c34,
const char * const s=0x02031748, const unsigned int len=0, const
unsigned long flags=524288)  Line 7711	C
   	perl512.dll!S_mess_alloc(interpreter * my_perl=0x01c45c34)  Line 1055
+ 0x12 bytes	C
   	perl512.dll!Perl_form(interpreter * my_perl=0x01c45c34, const char *
pat=0x01f75f18, ...)  Line 1113 + 0xf bytes	C
   	Win32.dll!boot_Win32(interpreter * my_perl=0x01ee046c, cv *
cv=0x01e9bff4)  Line 2495 + 0x7f bytes	C
   	perl519.dll!Perl_pp_entersub(interpreter * my_perl=0x01c466e8)
Line 2763	C
   	perl519.dll!Perl_runops_standard(interpreter * my_perl=0x01c45c34)
Line 42 + 0x4 bytes	C
   	perl519.dll!Perl_call_sv(interpreter * my_perl=0x01c45c34, sv *
sv=0x01e79b8c, volatile long flags=13)  Line 2747 + 0xc bytes	C
   	perl519.dll!Perl_call_list(interpreter * my_perl=0x01c45c34, long
oldscope=8, av * paramList=0x01c6ec34)  Line 4843	C
   	perl519.dll!S_process_special_blocks(interpreter *
my_perl=0x00000000, long floor=0, const char * const
fullname=0x01c795e0, gv * const gv=0x01dfc564, cv * const cv=0x01e79b8c)
   Line 7932	C
   	perl519.dll!Perl_newATTRSUB_flags(interpreter * my_perl=0x00000000,
long floor=43, op * o=0x01e6a9d0, op * proto=0x00000000, void *
attrs=0x2802c589, op * block=0x01e6a9f0, unsigned long flags=0)  Line
7894 + 0x16 bytes	C
   	perl519.dll!Perl_newATTRSUB(interpreter * my_perl=0x01c45c34, long
floor=43, op * o=0x01e6a9d0, op * proto=0x00000000, op *
attrs=0x00000000, op * block=0x01e6a9f0)  Line 7569 + 0x19 bytes	C
   	perl519.dll!Perl_utilize(interpreter * my_perl=0x00000000, int
aver=1, long floor=43, op * version=0x01e83744, op * idop=0x01e92f54, op
* arg=0x01e6f864)  Line 5317 + 0x7e bytes	C
   	perl519.dll!Perl_vload_module(interpreter * my_perl=0x01e92f54,
unsigned long flags=2, sv * name=0x01caf56c, sv * ver=0x01e83744, char *
* args=0x002df984)  Line 5463 + 0x23 bytes	C
   	perl519.dll!Perl_load_module(interpreter * my_perl=0x01c45c34,
unsigned long flags=2, sv * name=0x01caf56c, sv * ver=0x01e70154, ...)
Line 5405 + 0x16 bytes	C
   	perl519.dll!w32_CORE_all(interpreter * my_perl=0x01c45c34, cv *
cv=0x01c4bb84)  Line 33 + 0x3c bytes	C
   	perl519.dll!Perl_pp_entersub(interpreter * my_perl=0x01c4bb74)
Line 2763	C
   	perl519.dll!Perl_runops_standard(interpreter * my_perl=0x01c45c34)
Line 42 + 0x4 bytes	C
   	perl519.dll!Perl_call_sv(interpreter * my_perl=0x01c45c34, sv *
sv=0x01e099b4, volatile long flags=13)  Line 2747 + 0xc bytes	C
   	perl519.dll!Perl_call_list(interpreter * my_perl=0x01c45c34, long
oldscope=1, av * paramList=0x01d39f8c)  Line 4843	C
   	perl519.dll!perl_run(interpreter * my_perl=0x01c45c34)  Line 2359 +
0x12 bytes	C
   	perl519.dll!RunPerl(int argc=3, char * * argv=0x01c45be0, char * *
env=0x01c440e0)  Line 270 + 0x6 bytes	C++
   	perl.exe!__tmainCRTStartup()  Line 582 + 0x17 bytes	C
   	kernel32.dll!_BaseProcessStart@4()  + 0x28 bytes	

• Any empty members in struct xpvcv AKA CV that an XSUB can use? by bulk88
• Re: Any empty members in struct xpvcv AKA CV that an XSUB can use? by Father Chrysostomos
• Re: Any empty members in struct xpvcv AKA CV that an XSUB can use? by bulk88
• Re: Any empty members in struct xpvcv AKA CV that an XSUB can use? by Andy Dougherty
• Re: Any empty members in struct xpvcv AKA CV that an XSUB can use? by bulk88
• Re: Any empty members in struct xpvcv AKA CV that an XSUB can use? by Father Chrysostomos