4 replies to this topic

[hunguptodry]

following are 2 code fragments of the same function.
the only difference is the placement of the first line.
the first one crashes, the second does not.
does not crash on every call but is
consistent and repeatable.

I am using bloodshed Dev C++ 4.9.9.2

int posKong(int n, int tk) { int dp[144],tl[4],cnt = 0;

    int gp = _tiles[n].gp; int nm = _tiles[n].nm;

    int i,j,k; j = 0; for (i=0; i<144; i++) {

        if (_tiles[i].tk == tk && i != n) {

            if (_tiles[i].gp == gp &&

                _tiles[i].nm == nm) {

                cnt++;

            }

            dp[j++] = i;

        }

    }

    Bubble(tk,dp,j);

    if (cnt == 3) {

        k = 0; for (i=0; i<j; i++) {

            if (_tiles[dp[i]].gp == gp &&

                _tiles[dp[i]].nm == nm) {

                tl[k++] = i;

            }

        }

        if (abs(tl[2]-tl[0]) == 2) {

            return 1;

        }

    }

    return 0;

}

int posKong(int n, int tk) {

    int gp = _tiles[n].gp; int nm = _tiles[n].nm;

int dp[144],tl[4],cnt = 0;

    int i,j,k; j = 0; for (i=0; i<144; i++) {

        if (_tiles[i].tk == tk && i != n) {

            if (_tiles[i].gp == gp &&

                _tiles[i].nm == nm) {

                cnt++;

            }

            dp[j++] = i;

        }

    }

    Bubble(tk,dp,j);

    if (cnt == 3) {

        k = 0; for (i=0; i<j; i++) {

            if (_tiles[dp[i]].gp == gp &&

                _tiles[dp[i]].nm == nm) {

                tl[k++] = i;

            }

        }

        if (abs(tl[2]-tl[0]) == 2) {

            return 1;

        }

    }

    return 0;

}

[hunguptodry]

the function gets called quite often. several times each gameplay loop.
so i don't think it can be a fluke that the 1st version works.

[VilleK]

My guess is that when you change the position of that line it affects the stack layout of local variables and that previous to calling this function you have a bug that overwrites the stack (such as a out-of-bounds array access). See if your compiler has the option to build your project in a debug-build with guards against memory overwrites.

[hunguptodry]

yeah its probably stack corruption. maybe, i'll move all the local variables to globals (this is in the heap right?) and see if the problem goes away.
but then I already have a stack version that is fine.
so it'll be hard to conclude anything.
well, at least this is not a show stopper.

[AticAtac]

I am not sure, but you declared t1 with 4 elements:
"...int dp[144],tl[4],cnt = 0; ..."
and in the second loop you are using
"tl[k++] = i;"
and k may have exceed 3, put an assertion before this and make sure that k always be between 0 and 3.