Question

This may be a similar question to Linker errors 2005 and 1169 (multiply defined symbols) when using CUDA __device__ functions (should be inline by default), but not exactly. I’m getting several LNK2005 errors when trying to build a project (using code that has been shown to work elsewhere) on VS2010. I’m at my wits’ end.

For example, I have the following three files: transposeGPU.h, transposeGPU.cu, and transposeCUDA.cu. transposeGPU.h can be summarized as follows:

void transposeGPU(float *d_dst, size_t dst_pitch,
    float *d_src, size_t src_pitch,
    unsigned int width, unsigned int height);

i.e., a single declaration without any includes. The definition of that function is found in transposeGPU.cu, which can be summarized as follows:

#include <stdio.h>
#include "../transposeGPU.h"
#include "../helper_funcs.h"

#include "transposeCUDA.cu"

void
transposeGPU(float *d_dst, size_t dst_pitch,
    float *d_src, size_t src_pitch,
    unsigned int width, unsigned int height)
{
    // execution configuration parameters
    dim3 threads(16, 16);
    dim3 grid(iDivUp(width, 16), iDivUp(height, 16));
    size_t shared_mem_size =
        (threads.x * threads.y + (threads.y - 1)) * sizeof(float);

    transposeCUDA<<<grid, threads, shared_mem_size>>>(
        d_dst, dst_pitch / sizeof(float),
        d_src, src_pitch / sizeof(float),
        width, height);
}

i.e., tranposeGPU.cu includes its header file and transposeCUDA.cu, besides defining transposeGPU() and calling transposeCUDA(), the latter found in transposeCUDA.cu. Now, transposeCUDA.cu defines the function as expected:

#include "common_kernel.h"

__global__ void
transposeCUDA(
    float *g_dst, size_t s_dst_pitch,
    const float *g_src, size_t s_src_pitch,
    unsigned int img_width, unsigned int img_height)
{
// several lines of code...
}

It all looks in order, but I still get error LNK2005: "void __cdecl __device_stub__Z13transposeCUDAPfjPKfjjj(float *,unsigned int,float const *,unsigned int,unsigned int,unsigned int)" (?__device_stub__Z13transposeCUDAPfjPKfjjj@@YAXPAMIPBMIII@Z) already defined in transposeCUDA.obj in transposeGPU.obj.

That and some twenty other similar linker errors. Why? There’s no apparent redefinition occurring. Any help would be greatly appreciated.

Answer 1

There is a redefinition occurring if you are compiling both transposeCUDA.cu and transposeGPU.cu, since the definition appears in both translation units. You should not #include transposeCUDA.cu and apply nvcc to that file.