Cuda C - Linker error - undefined reference

c, cuda, linker-errors

Solution

You have a problem with symbol name mangling. `nvcc` uses the host C++ compiler to compile host code, and this implies that symbol name mangling is applied to code emitted by the CUDA toolchain.

There are two solutions to this problem. The first is to define `dummy_gpu` using C linkage, so change your `my_cuda.cu` to something like this:

extern "C" {
#include "my_cuda.h"
}

.....


extern "C"
void dummy_gpu(){
   dummy_gpu_kernel<<<128,128>>>();
}

Note that you will need to change your linkage command to this:

gcc -L/usr/local_rwth/sw/cuda/5.0.35/lib64 -o md.exe main.o my_cuda.o -lcuda -lcudart

because the CUDA shared libraries need to be specified after the object files that use them.

Your second alternative would be to use either `g++` or `nvcc` to do the linking, in which case the whole problem should disappear.

Problem

I am having a hard time compiling a simple cuda program consiting of only two files. The main.c looks like this: ``` #include "my_cuda.h" int main(int argc, char** argv){ dummy_gpu(); } ``` The cuda.h looks like this: ``` #ifndef MY_DUMMY #define MY_DUMMY void dummy_gpu(); #endif ``` And the my_cuda.cu file loos like this: ``` #include <cuda_runtime.h> #include "my_cuda.h" __global__ void dummy_gpu_kernel(){ //do something } void dummy_gpu(){ dummy_gpu_kernel<<<128,128>>>(); } ``` However if I compile I allways receive the following error: ``` gcc -I/usr/local/cuda/5.0.35/include/ -c main.c nvcc -c my_cuda.cu gcc -L/usr/local_rwth/sw/cuda/5.0.35/lib64 -lcuda -lcudart -o md.exe main.o my_cuda.o main.o: In function `main': main.c:(.text+0x15): undefined reference to `dummy_gpu' collect2: ld returned 1 exit status ``` Thank you for your help.

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