debugging - error code (-11):: what are all possible reasons of getting error "cl_build_program_failure" in OpenCL?

Question

I am using ATI RV770 graphics card, OpenCl 1.0 and ati-stream-sdk-v2.3-lnx64 on linux.

While running my host code which includes following two sections to build kernel program, i am getting error code (-11) i.e. cl_build_program_failure. Does it means that kernel program compiled, if not then how is it compiled and debugged?

const char* KernelPath = "abc_kernel.cl";   //kernel program is in separate file but in same directory of host code..

/* Create Program object from the kernel source *******/

char* sProgramSource = readKernelSource(KernelPath);
size_t sourceSize =  strlen(sProgramSource) ;
program = clCreateProgramWithSource(context, 1,(const char **) &sProgramSource,&sourceSize, &err);
checkStatus("error while creating program",err);

/* Build (compile & Link ) Program *******/

char* options = (char* )malloc(10*sizeof(char));
strcpy(options, "-g");
err = clBuildProgram(program, num_devices, devices_id, options, NULL, NULL);
checkStatus("Build Program Failed", err); //This line throwing the error....

function to read kernel program is as follows::

/* read program source file*/

char* readKernelSource(const char* kernelSourcePath){
 FILE    *fp = NULL;
 size_t  sourceLength;
 char    *sourceString ;
 fp = fopen( kernelSourcePath , "r");
 if(fp == 0)
 {
        printf("failed to open file");
        return NULL;
 }
 // get the length of the source code
 fseek(fp, 0, SEEK_END);
 sourceLength = ftell(fp);
 rewind(fp);
 // allocate a buffer for the source code string and read it in
 sourceString = (char *)malloc( sourceLength + 1);
 if( fread( sourceString, 1, sourceLength, fp) !=sourceLength )
 {
          printf("
 Error : Fail to read file ");
          return 0;
 }
 sourceString[sourceLength+1]='';
 fclose(fp);
 return sourceString;

}// end of readKernelSource

Can anyone tell how to fix it?

Does it means that it is OpenCl compilation error at runtime or something else?

//Printing build_log info using clGetProgramBuildInfo() as below, But why is is not printing anything?

char* build_log; size_t log_size;

// First call to know the proper size
        err = clGetProgramBuildInfo(program, devices_id, CL_PROGRAM_BUILD_LOG, 0, NULL, &log_size);
        build_log = (char* )malloc((log_size+1));

        // Second call to get the log
        err = clGetProgramBuildInfo(program, devices_id, CL_PROGRAM_BUILD_LOG, log_size, build_log, NULL);
        build_log[log_size] = '';
        printf("--- Build log ---
 ");
        fprintf(stderr, "%s
", build_log);
        free(build_log);

Answer 1

This error is typically caused by a syntax error in your kernel code. You can call the OpenCL function clGetProgramBuildInfo with the flag CL_PROGRAM_BUILD_LOG to access the log generated by the compiler. This log contains the output you are probably used to when compiling on the command-line (errors, warnings, etc.).

For example, you could add something similar to the following after you call clBuildProgram:

if (err == CL_BUILD_PROGRAM_FAILURE) {
    // Determine the size of the log
    size_t log_size;
    clGetProgramBuildInfo(program, devices_id[0], CL_PROGRAM_BUILD_LOG, 0, NULL, &log_size);

    // Allocate memory for the log
    char *log = (char *) malloc(log_size);

    // Get the log
    clGetProgramBuildInfo(program, devices_id[0], CL_PROGRAM_BUILD_LOG, log_size, log, NULL);

    // Print the log
    printf("%s
", log);
}

You can also see the function buildOpenCLProgram() in SDKCommon.cpp in the AMD APP SDK for a real example.