[gambit-list] executable works, loadable module segfaults

Mikael mikael.rcv at gmail.com
Fri Sep 28 05:42:32 EDT 2012


What inspired you to the particular design of string_to_SCMOBJ (things like
___CTOS_HEAP_OVERFLOW_ERR+arg_num;)?

2012/9/28 Mikael <mikael.rcv at gmail.com>

> Just to start, are you sure that when you return that string, that it
> remains on the C heap somewhere all until your string_to_SCMOBJ procedure
> digests it?
>
> I mean, if it's on the stack, then probably it's overwritten by the
> subsequent C procedure call to string_to_SCMOBJ, which consumes stack space
> (the unsigned int and ___SCMOBJ in string_to_SCMOBJ should take the first
> positions of stack space that f1b_hello previously occupied, and thus
> destroy the structure?).
>
> If it had been a char* constant you had returned instead, I suppose the C
> compiler would have put it in some separate, reserved area.
>
> Well just a wild guess.
>
>
> What about adding Lots of debug printf:s in string_to_SCMOBJ as to check
> that it produces the right thing.
>
>
> Last, in your type definition (c-define-type string "string"
> "string_to_SCMOBJ" "SCMOBJ_to_string" #f) you use #f for release function
> i.e. afaik free()?
>
> That's not the right thing right, you'd want C++' delete or sth..?
>
> Also why is not the string type you use pointered? Please correct me on
> this one.
>
>  Brgds
>
> 2012/9/28 REPLeffect <repleffect at gmail.com>
>
>>  I came across a strange behavior with Gambit Scheme on Windows (XP, in
>> this case).  I wrote a module to convert C++ std::string types to
>> Gambit char-strings.  I wanted to use that in a loadable module.  This
>> all works fine on Linux, but I also need to use it on Windows.  I'm
>> using MinGW's C++ compiler (g++ version 4.6.2 -- which I also used to
>> compile Gambit).  And I'm still on version 4.6.5 of Gambit Scheme.
>>
>> I've attached a zipped tar file with an example (6 files, including a
>> build.windows script and a build.linux script).
>>
>> When I load the shared module in gsi on Windows XP, it segfaults in
>> ___garbage_collect(long) -- I believe it was in the call to
>> ___alloc_scmobj.  When I load it on Linux it works just fine.  The
>> executable built by the scripts on both platforms works just fine.
>>
>> I would love to know what is causing this.  I've spent many hours
>> trying to find the source of the problem, and finally narrowed it down
>> to this.
>>
>> Any help/explanations/suggestions would be much appreciated.
>>
>> repleffect
>>
>> _______________________________________________
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>> Gambit-list at iro.umontreal.ca
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>>
>>
>
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