Undeclared first use of function

It gave me the undeclared first use of function:

Code:

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#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;

#define max_size = 100;

int main ()
{

    //float instrs[max_size];
 FILE * fin;
 fin = fopen("test.txt", "r");
unsigned int oneinst;
int i;

while (!feof(fin))
      {
    fscanf(fin, "%x", &oneinst);
    int    instrs[] = {oneinst};
      }

for(int i = 0; i < 5; i++)

        {

        int opcode = (instrs[i] >> 26) & 0x3F;
          } 
 

    return 0;
}

For reason when I run this I get the error: `instrs' undeclared (first use this function)

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:confused:

If you indented the code properly, the reason might become apparent:

Code:

---

#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;

#define max_size = 100;

int main()
{
    //float instrs[max_size];
    FILE* fin;
    fin = fopen("test.txt", "r");
    unsigned int oneinst;
    int i;

    while (!feof(fin))
    {
        fscanf(fin, "%x", &oneinst);
        int instrs[] = {oneinst};
    }

    for (int i = 0; i < 5; i++)
    {
        int opcode = (instrs[i] >> 26) & 0x3F;
    }

    return 0;
}

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As you can see, instrs is local to the while loop, so it does not exist in the for loop. You should have declared it before the loops by uncommenting:

Code:

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float instrs[max_size];

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Though it looks like instrs should be an array of int, not float. Also, this would then be wrong:

Code:

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#define max_size = 100;

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You could have written:

Code:

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const int max_size = 100;

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You should not use feof to control a loop like that (why not just use C++-style I/O?), and then you need to make other changes to get your program to work.

Thank you very much laserlight, you have been more than helpful

Quote:

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Originally Posted by TheXx11

what is this C++ I/O style, what do I need to google search to find out more about it?

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You already #include <iostream>. Search for that.