On May 3, 2009, at 9:20 PM, John E. Malmberg wrote:
John E. Malmberg wrote:
Perl_sv_upgrade(pTHX_ register SV *const sv, svtype new_type)case SVt_PVMG: ... new_body_inline(new_body, new_type); new_type = SVt_PVMG, SVt_PVMG has a value of 7. new_body = 44. PL_Body_roots[sv_type] = 44.From the code, it looks like this was expected to contain a valid pointer.From looking at the source code, it appears that the linked list of bodies is corrupted. my_perl->Ibodyroots[7] has 44.
Yes, I see the same thing.
I have been looking at the S_more_bodies routine. Would it be practical to put an assert on for a pointer being added to the linked list with a value above 512? On VMS, the first page of memory is protected no access.
I haven't had much time to poke at this, but I think an assert there would only help if the body is created with a bogus pointer in the SVt_PVMG slot rather than created with a good pointer that gets clobbered later, and I think the second explanation is more likely. I merely observe (without yet a chance fully to pursue) that 44 is a suspicious number on a couple of different fronts.
Running with -Dm shows that various 44-byte chunks of memory get allocated, including arenas that are multiples of 44 in size, so if there is a legitimate size of 44 that is added to something that should be a good value but is actually NULL, that might be one explanation for where the bad smell is coming from.
44 / 0x2c is the value of SS$_ABORT, which is the return value of the system() call in IPC::Cmd::_run, which is called somewhere in the chain following from CPANPLUS::Dist::_resolve_prereqs.[1] If there is something inappropriate going on with a vmsish pragma and the return value of the system() call, that's another place where something could go wrong, but also as yet another wacky theory that I haven't been able to prove.
I've attached a version of the test script that is slimmed down from 400+ lines to 99 lines but still produces the access violation.
[1] IPC::Cmd::_run does not quote arguments, so in its current form it's not really suitable as a cross-platform way to run Perl one- liners. For example, when it means to run:
perl "-M10000000000" "-e1"
Perl v1410065408.0.0 required--this is only v5.11.0, stopped.
BEGIN failed--compilation aborted.
%SYSTEM-F-ABORT, abort
it's actually running:
$ perl -M10000000000 -e1
syntax error at -e line 0, near "use 10000000000 ("
Execution of -e aborted due to compilation errors.
%SYSTEM-F-ABORT, abort
So the CPANPLUS::Dist test is not distinguishing between a syntax
error and a version check failure. I don't think it makes any
difference for the access violation, but it's something I noticed
while trying to pursue that.
________________________________________ Craig A. Berry mailto:craigbe...@mac.com "... getting out of a sonnet is much more difficult than getting in." Brad Leithauser
19_CPANPLUS-Dist.t
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