fopen fails with absolute path

Am trying to experiment file based operations inside FVP environment , my intention is to pass the inputs via FILE for a Unit testing a function inside FVP  in DS.  

FILE *fp = fopen("D:\arm_ds5\sve2_matmul_f64\test.txt","r");
if(fp == NULL)
printf("cannot read file ");   --> always getting this print since File is not found , Kindly suggest the workaround for the same