GCC: Compiling an OpenCL host on Windows

Question

I just wanted to try out using OpenCL under Windows.

Abstract: I got an "undefined reference to" error when I tried to compile (using the command gcc my.o -o my.exe -L "C:\Program Files (x86)\AMD APP\lib\x86_64" -l OpenCL).

---

My Code

#include <CL/cl.h>
#include <stdio.h>

int main(void) {   
    cl_platform_id platform;
    int err;

    err = clGetPlatformIDs(1, &platform, NULL);
    if(err < 0) {
        perror("There's No Platform!");
        exit(1);
    }

    /* Some more code... */

    system("PAUSE");
}

Makefile

all: addition

addition:
    gcc -c -I "C:\Program Files (x86)\AMD APP\include" my.c -o my.o
    gcc my.o -o my.exe -L "C:\Program Files (x86)\AMD APP\lib\x86_64" -l OpenCL

Used Programs

• MinGW's gcc
• Visual Studio's nmake
• AMD's OpenCL™ APP SDK (that's where I took the OpenCL library and the CL.h file from)

The Structure of APP SDK's Folders

%>tree /F "C:\Program Files (x86)\AMD APP\lib\x86_64"
Auflistung der Ordnerpfade
Volumeseriennummer : D2DC-D765
C:\PROGRAM FILES (X86)\AMD APP\LIB\X86_64
    libOpenCL.a
    OpenCL.lib
    OpenVideo64.lib

Es sind keine Unterordner vorhanden


%>tree /F "C:\Program Files (x86)\AMD APP\include"
Auflistung der Ordnerpfade
Volumeseriennummer : D2DC-D765
C:\PROGRAM FILES (X86)\AMD APP\INCLUDE
├───CAL
│       cal.h
│       calcl.h
│       cal_ext.h
│       cal_ext_counter.h
│       cal_ext_d3d10.h
│       cal_ext_d3d9.h
│
├───CL
│       cl.h
│       cl.hpp
│       cl_d3d10.h
│       cl_ext.h
│       cl_gl.h
│       cl_gl_ext.h
│       cl_platform.h
│       opencl.h
│
└───OpenVideo
        OpenVideo.h
        OVDecode.h
        OVDecodeTypes.h
        OVEncode.h
        OVEncodeTypes.h

Error Message

        gcc addition.o -o addition.exe -L "C:\Program Files (x86)\AMD APP\lib\x86_64" -l OpenCL
addition.o:addition.c:(.text+0x2d): undefined reference to `clGetPlatformIDs@12'
addition.o:addition.c:(.text+0x83): undefined reference to `clGetDeviceIDs@24'
addition.o:addition.c:(.text+0xc2): undefined reference to `clGetDeviceIDs@24'
collect2: ld returned 1 exit status
NMAKE : fatal error U1077: "C:\prog-x86\MinGW\bin\gcc.EXE": Rückgabe-Code "0x1"
Stop.

My Questions

My questions are simple:

• Why doesn't my code compile how it is expected to?
• What can I do to get rid of this problem?

Thanks.

---

UPDATE: The error message after dropping the spaces like described in @codaddict 's answer.

(Makefile)

all: addition

addition:
  gcc -c -I "C:\prog-x86\AMD-APP\include" addition.c -o addition.o
  gcc addition.o -o addition.exe -LC:\prog-x86\AMD-APP\lib\x86_64 -lOpenCL

(Shelldata)

%>nmake

Microsoft (R) Program Maintenance Utility, Version 11.00.50727.1
Copyright (C) Microsoft Corporation. Alle Rechte vorbehalten.

        gcc -c -I "C:\Program Files (x86)\AMD APP\include" addition.c -o addition.o
addition.c: In function 'main':
addition.c:14:9: warning: incompatible implicit declaration of built-in function 'exit' [enabled by d
efault]
addition.c:23:9: warning: incompatible implicit declaration of built-in function 'exit' [enabled by d
efault]
        gcc addition.o -o addition.exe -LC:\prog-x86\AMD-APP\lib\x86_64 -lOpenCL
addition.o:addition.c:(.text+0x2d): undefined reference to `clGetPlatformIDs@12'
addition.o:addition.c:(.text+0x83): undefined reference to `clGetDeviceIDs@24'
addition.o:addition.c:(.text+0xc2): undefined reference to `clGetDeviceIDs@24'
collect2: ld returned 1 exit status
NMAKE : fatal error U1077: "C:\prog-x86\MinGW\bin\gcc.EXE": Rückgabe-Code "0x1"
Stop.

%>

Answer 1

The default MinGW distribution only ships tools for building x86 applications. You cannot link against the x64 version of the OpenCL library. So you either have to use MinGW-w64 or use the x86 version (change the library path to the x86 subfolder of the APP SDK).

Answer 2

Try changing

-l OpenCL

to

-lOpenCL

in the compile line.

The -l option of gcc expects the name of the library (without the lib prefix) right next to it without any space. Remember using -lm in school to link to libm?