havin error code -38 in opencl ?

i am having error code -38 when i print err or status of clEnqueueReadBuffer (…)
pls help what does it mean?

i have solved the problem by writing NULL in destination array in which i am storing the value of addition of two source arrays value,i am posting the code but pls help me to tell the reason why it has happened when change it to NULL

float a[100],b[100];,c[100];
//For addition c[i]=a[i]+b[i];
cl_mem d_A,d_B,d_C; //mem object
d_A =clCreateBuffer(context,CL_MEM_READ_ONLY|CL_MEM_COPY_HOST_PTR,
d_B= clCreateBuffer(context,CL_MEM_READ_ONLY|CL_MEM_COPY_HOST_PTR,

the above 2 statements are same,but when i do change from “c to NULL” in below statment it works fine
pls tell the reason why it is happening if i write c then error and if NULL it works fine

N*sizeof(float),c,&err);//here is the problem why i cant write c ,as did in above two statement,why i have to put NULL instead of c (which is same is array as a & b)when destination mem object i have to create on gpu…

pls help

sorry this statement mis written it contains CL_MEM_WRITE_ONLY

rest is same in above question

Could it be the extra semicolon here:

float a[100],b[100];,c[100];

(after b before c)