OpenCL. clBuildProgram with relative path for headers


Could someone help me. I am using CUDA SDK and have a problem with headers including in cl-files.

Let full path to project be C:\FULL\PATH\TO\PROJECT, and its content is something like:

________|- include
________________|- cl_header1.h

In cl_header1.h:

#include <cl_header1.h>
__kernel void cl_kernel(...)

In some_code.cpp:

err = clBuildProgram(program, 1, &device_id, include_path.c_str(), NULL, NULL);

If include_path is full:

string include_path = "-I C:\\FULL\\PATH\\TO\\PROJECT\\cl\\include";

program runs, but if I set it as relative

string  include_path = "-I \\cl\\include";

clBuildProgram fails.

What I am doing wrong?