Pl_Query_Call crash on windows (MacOSX OK)

[Sarah Smith]

Hi,

First off would like to say thanks to the authors of gprolog for a great prolog implementation and an nice cross-platform distribution.

I'm working on a text adventure game as a personal project, using prolog for the game logic, and C++/Qt for the UI.

The plan is to release it on Mac (my main development platforrm), Windows (I run XP in a VM just for this purpose) and Linux.  My day job is writing C++ code, and I know my way around compilers.

As soon as I got past first base, with some game logic and a UI working, I wanted to build a release on all platforms to make sure things are all working.

But while things work well on Mac - after a couple of teething problems - I'm stuck with a crash bug on Windows.

The problem is occurring in my "do_command" function when I call Pl_Query_Call:

extern "C" void do_command(const char *command)

{

    int func;

    int res;

    PlTerm arg[512];

    char cmd[512];

    PlTerm list;

    func = Find_Atom("do_command");

    if (func)

    {

        Pl_Query_Begin(PL_TRUE);

        i = 0;

        k = 0;

        list[0] = NULL;

        while (command[i])

        {

            /* parse each token out into cmd */

            arg[k++] = Mk_String(cmd);

        }

        if (k)

            list = Mk_Proper_List(k, arg);

        res = Pl_Query_Call(func, 1, list);

        while (res)

            res = Pl_Query_Next_Solution();

        Pl_Query_End(PL_RECOVER);

    }

}

I've cut out some detail but the full source code is here: http://gitorious.org/ethex2040/ethex2040/blobs/master/prolog.cpp#line43

I compiled gprolog from source so I could use it in debug mode, but the stack trace is not helpful.  At least it shows the site of the crash.

When the above function processes a command, I get a SIGSEGV crash on line 69 of file unify.c in the function Pl_Unify:

Bind_UV(u_adr, v_word)

I presume there's something wrong with the u_adr pointer.  But the other frames in the stack are assembler and so far I'm mystified as to how to trace what is going wrong.

Any ideas?

Regards,

Sarah Smith