Ok, thanks. My final solution for 1st problem:
in userimg.jl I have added this line: demo(x::Vector{UInt8}) = println("x: ", utf8(x)) and in start_func.c I have this code: #include <julia.h> #include <stdio.h> int main() { jl_init_with_image(NULL, "libMyJuliaImage.dll"); int utf8_length = 6; jl_value_t* array_type1 = jl_apply_array_type(jl_uint8_type, 1); jl_array_t* utf8_str = jl_alloc_array_1d(array_type1, utf8_length); JL_GC_PUSH1(&utf8_str); char* data = jl_array_data(utf8_str); data[0] = 'H'; data[1] = 'E'; data[2] = 'L'; data[3] = 'L'; data[4] = 'O'; data[5] = '!'; jl_function_t *func = jl_get_function(jl_current_module, "demo"); jl_call1(func, (jl_value_t*) utf8_str); JL_GC_POP(); int ret_val = 0; jl_atexit_hook(ret_val); return ret_val; } In C I work with uint8(char) array without '\0' and in julia i need convert this array with utf8() function.