Js-ctypes char readString() makes Mozilla crash

Question

I am using js-sctypes to connect to a shared library in Linux from Firefox. I am declaring a function from the library as follows:

var read_memory = libc.declare("read_memory", ctypes.default_abi, ctypes.int,
                   ctypes.uint32_t, ctypes.char.ptr, ctypes.int, ctypes.int);

In C++ library this function is declared as follows:

read_memory(unsigned int address, char *buf, int unit_size, int unit_count)

I am calling the read_memory function in the following way:

var my = new ctypes.char().address();
read_memory(0, my, 4, 1);
st = st + my.readString();

And it works fine, but when I am calling the function with greater unit_size and unit_count, for example read_memory(0, my, 4, 10), the Firefox crashes.

Is it because ctypes.char is limited in size, or there is another reason for this fault? Any help on this matter would be appreciated.

Thank you.

Answer 1

I had the same problem and the problem is because of character encoding. In my problem I need to convert them from windows-1250 to utf-8.

I used code below:

result = myFunctionToInvoke();
var util = priv.Load("LibToConvert.dll");
var wi12502utf8 = util.declare("win12502utf8", ctypes.default_abi, ctypes.char.ptr, ctypes.char.ptr);
var val = wi12502utf8(result);
result = val.readString();

In this code I created my own lib (LibToConvert.dll) in C++ to convert characters.