clBuildProgram failed with error code -11 and without build log - opencl

Question

I have worked little bit in OpenCL now but recently "clBuildProgram" failed in one of my program. My code excerpt is below:
cl_program program;
program = clCreateProgramWithSource(context, 1, (const char**) &kernel_string, NULL, &err);
if(err != CL_SUCCESS)
{
cout<<"Unable to create Program Object. Error code = "<<err<<endl;
exit(1);
}
if(clBuildProgram(program, 0, NULL, NULL, NULL, NULL) != CL_SUCCESS)
{
cout<<"Program Build failed\n";
size_t length;
char buffer[2048];
clGetProgramBuildInfo(program, device_id[0], CL_PROGRAM_BUILD_LOG, sizeof(buffer), buffer, &length);
cout<<"--- Build log ---\n "<<buffer<<endl;
exit(1);
}
Normally earlier I got syntax or other errors inside kernel file here with the help of "clGetProgramBuildInfo()" function whenever "clBuildProgram" Failed but when this program runs, on console it only prints:
Program Build failed
--- Build log ---
And when I tried to print the error code returned by "clBuildProgram"; it is "-11"......
What can be the problem with my kernel file that I dont get any build fail information ?

Answer 1

You can learn the meaning of OpenCL error codes by searching in cl.h. In this case, -11 is just what you'd expect, CL_BUILD_PROGRAM_FAILURE. It's certainly curious that the build log is empty. Two questions:
1.) What is the return value from clGetProgramBuildInfo?
2.) What platform are you on? If you are using Apple's OpenCL implementation, you could try setting CL_LOG_ERRORS=stdout in your environment. For example, from Terminal:
$ CL_LOG_ERRORS=stdout ./myprog
It's also pretty easy to set this in Xcode (Edit Scheme -> Arguments -> Environment Variables).

Answer 2

If you are using the C instead of C++:
err = clBuildProgram(program, 0, NULL, NULL, NULL, NULL);
////////////////Add the following lines to see the log file///////////
if (err != CL_SUCCESS) {
char *buff_erro;
cl_int errcode;
size_t build_log_len;
errcode = clGetProgramBuildInfo(program, devices[0], CL_PROGRAM_BUILD_LOG, 0, NULL, &build_log_len);
if (errcode) {
printf("clGetProgramBuildInfo failed at line %d\n", __LINE__);
exit(-1);
}
buff_erro = malloc(build_log_len);
if (!buff_erro) {
printf("malloc failed at line %d\n", __LINE__);
exit(-2);
}
errcode = clGetProgramBuildInfo(program, devices[0], CL_PROGRAM_BUILD_LOG, build_log_len, buff_erro, NULL);
if (errcode) {
printf("clGetProgramBuildInfo failed at line %d\n", __LINE__);
exit(-3);
}
fprintf(stderr,"Build log: \n%s\n", buff_erro); //Be careful with the fprint
free(buff_erro);
fprintf(stderr,"clBuildProgram failed\n");
exit(EXIT_FAILURE);
}

Answer 3

I encountered the same problem with an empty log file. I was testing my ocl kernel on a different computer. It had 2 platforms instead of one. One Intel GPU and one AMD GPU. I only had AMD OCL SDK installed. Installing the Intel OCL SDK fixed the problem. Also selecting the AMD platform instead of the Intel GPU platform fixed it.

Answer 4

I've seen this happen on OSX 10.14.6 when the OpenCL kernel source is missing the _kernel attribute tag. If both the _kernel tag and return type are missing it seems to crash the system OpenCL compiler daemon, which then takes a few seconds to restart before new kernels will compile again.