Writing to file in Visual Studio C

Question

So after trying out the solutions I implemented them and I get output as "Exit".

I am trying to write to some file, preferably csv file. Bu any file I write to, throws an error message, attached.I do not know what is going wrong.

This is my code in Visual Studio 2015 C

#define TRANSFER_LENGTH_FROM_HOST (128)                 //Burst input
#define TRANSFER_LENGTH_FROM_FPGA (128)                // Burst output
#define NUM_TRANSFERS (50)                

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "ZestSC2.h"

void ErrorHandler(const char *Function, ZESTSC2_HANDLE Handle, ZESTSC2_STATUS Status, const char *Msg)
{
       printf("**** Example2 - Function %s returned an error\n \"%s\"\n\n", Function, Msg);
       exit(1);
}

int main(int argc, char **argv)
{
    unsigned long Count;
    unsigned long NumCards;
    unsigned long CardIDs[256];
    unsigned long SerialNumbers[256];
    ZESTSC2_FPGA_TYPE FPGATypes[256];
    ZESTSC2_HANDLE Handle;
    unsigned __int64 Freq;
    unsigned __int64 Start;
    unsigned __int64 End;
    unsigned long *Buffer_tx;
    unsigned long *Buffer_rx;

    FILE *fp;
    errno_t err = fopen_s(&fp, "C:/Users/Shankhadeep/Documents/results.csv", "w+");

    // Install an error handler
    ZestSC2RegisterErrorHandler(ErrorHandler);

    // Request information about the system
    ZestSC2CountCards(&NumCards, CardIDs, SerialNumbers, FPGATypes);

    printf("%d available cards in the system\n\n\n", NumCards);

    if (NumCards==0)
    {
        printf("No cards in the system\n");
        exit(1);
    }

    for (Count=0; Count<NumCards; Count++)
        printf("%d : CardID = 0x%08lx, SerialNum = 0x%08lx, FPGAType = %d \n \n", Count, CardIDs[Count], SerialNumbers[Count], FPGATypes[Count]);

    // Open the first card
    ZestSC2OpenCard(CardIDs[0], &Handle);

    printf("Reading the bit file .. \n");

    if (FPGATypes[0] == ZESTSC2_XC3S2000)
        ZestSC2ConfigureFromFile(Handle, "C:/Users/Shankhadeep/Documents/Example2_4000.bit");
    else
        ZestSC2ConfigureFromFile(Handle, "C:/Users/Shankhadeep/Documents/example2.bit");

    // Send data to the card - Generate a 64-bit random number in Buffer
    Buffer_tx = malloc(TRANSFER_LENGTH_FROM_HOST);
    Buffer_rx = malloc(TRANSFER_LENGTH_FROM_FPGA);

    for (Count = 1; Count < TRANSFER_LENGTH_FROM_HOST / 2; Count++) {
        ((unsigned long *)Buffer_tx)[Count] = (unsigned long)(1 << (Count - 1));
        printf("Writing %x \n", Buffer_tx[Count]);
    }

    QueryPerformanceFrequency((LARGE_INTEGER *)&Freq);
    QueryPerformanceCounter((LARGE_INTEGER *)&Start);
   for (Count=0; Count<NUM_TRANSFERS; Count++)
   {
        ZestSC2WriteData(Handle, Buffer_tx, TRANSFER_LENGTH_FROM_HOST);
        for (Count = 0;Count<TRANSFER_LENGTH_FROM_HOST / 2; Count++)
            //fwrite(Buffer_tx, 64, 128, fp);
            //Throws an error as soon as I write this line
            fprintf(fp, "%s", Buffer_tx[Count]);
    }
    QueryPerformanceCounter((LARGE_INTEGER *)&End);
    printf("Transfer rate to card = %.2fMBytes/sec\n", ((double)NUM_TRANSFERS*(double)TRANSFER_LENGTH_FROM_HOST*(double)Freq)/(1024.*1024.*(double)(End-Start)));

    // Read data from the card
    QueryPerformanceCounter((LARGE_INTEGER *)&Start);
   // for (Count=0; Count<NUM_TRANSFERS; Count++)
   // {
        ZestSC2ReadData(Handle, Buffer_rx, TRANSFER_LENGTH_FROM_FPGA);
        for (Count = 0; Count < 64; Count++) {
            printf("Reading %x \n", Buffer_rx[Count]);

        }
  //  }
    QueryPerformanceCounter((LARGE_INTEGER *)&End); 
    printf("\n");
    printf("Transfer rate from card = %.2fMBytes/sec\n", 
        ((double)NUM_TRANSFERS*(double)TRANSFER_LENGTH_FROM_FPGA*(double)Freq)/(1024.*1024.*(double)(End-Start)));
    printf("End : %d Start: %d \n", End, Start);

    if (!fp)perror("fopen_s");
printf("Error is %d", err);

if (err != NULL)
    fprintf(fp, "Hello");
else printf("Exit \n");
    ZestSC2CloseCard(Handle);
    return 0;
}

The error I am getting is

Debug Assertion Failed!
Program .. fpga_2_host.exe 
File minkernel\crts\ucrt\src\appcrt\stdio\output.cpp Line 31
Expression: stream != nullptr

Answer 1

You're using the return of fopen_s incorrectly (It returns an error code). The first argument is all you need to set the data into fp.

errno_t err = fopen_s(&fp, "C:/Users/Shankhadeep/Documents/results.csv", "w+");