This cpp code crash. Everytime I input a string of length 4, malloc in vector fails

I am using this program to store the values I input in the nxn matrix.

The first input is number of test cases. The second is the value of n. So I create a n*n matrix. Then I input the values for each row Ex: .... The input is always a combination of '.' or '#'.

Here is a part of the code I am using:

int main() {
    // Read the data
    int total_test = 0;
    int tmp, val = 0;
    std::string tmp_s;

    std::cin >> total_test;
    // RUn it total_test number of time
    for (; total_test; total_test--) {
        std::cin >> val;
        matrix path = matrix(val);
        // Parse input
        for (int row = val; row; row--) {
            std::cin >> tmp_s;
            std::vector<char> chars(tmp_s.begin(), tmp_s.end());
            for(int col = val-1; col >= 0; col--) {
                if (chars[col] == '#')
                    path.row[row][COL(val, row, col)] = -1;
            }
        }

    }
    return 0;
}

I run this program and everytime I give the input string to read as "...." this program crashes. I know the exact line where this occurs..

Its either cin >> tmp_s; (I am pretty sure think this is not the line) Its this line: std::vector chars(tmp_s.begin(), tmp_s.end());

The GDB has this to say! Can anyone help me with this? Thanks.

(gdb) s
57              std::cin >> tmp_s;
(gdb) 
....
a.out: malloc.c:2372: sysmalloc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 *(sizeof(size_t))) - 1)) & ~((2 *(sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long) old_end & pagemask) == 0)' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff7531cc9 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56  ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) 

Thanks! :)