warning: unused variable

see in one code i have written

void my_function()
{
INT32开发者_StackOverflow中文版 i;    /* Variable for iteration */ 
/* If system is little-endian, store bytes in array as reverse order */
#ifdef LITTLE   
   {    
    // i m using i for operating one loop 
   }
#endif

 /* If the system is big-endian, store bytes in array as forward order */
#ifdef  BIG 
   {
   // using i for loop
   }
#endif
return;
 }

by compiling this code with -Wall flag it shows

 warning: unused variable ‘i’      

why? how can i remove this?

---

Put the declaration of i just inside the {} where you actually use it. Even better if you have C99, declare the loop variable inside the for(int i = 0, i < bound; ++i)

---

By defining either LITTLE or BIG. I doubt many compilers give that warning for this code when one of those symbols are defined. If you still have the warning, then you might change the second #ifdef to an #else.

I don't see any #endif anywhere -- presumably in the real code, those appear.

---

You need to define either BIG or LITTLE (as mentioned elsewhere).

In order to stop this happening again in the future, you can raise a specific compile-time error using the following:

#if !defined LITTLE && !defined BIG
#error You haven't defined one of your macro names
#endif

Alternatively, you could include i only when using either code block by surrounding it with #if defined as well:

#if defined LITTLE || defined BIG
INT32 i;
#endif

In both cases, note the keyword to use is #if not #ifdef or #ifndef.

---

You do not have to declare the iteration number. Just do it in your for statement.

for(int i = 0; i < 6; i++){
  // insert loop code here

}

---

hey i got the answer...

see BIG & LITTLE are preposser flag & they are given at compile time. when i was compiling my project with make file i was giving this flag at compile time but while testing each individual file i was compiling like

gcc -Wall -c filename.c 

This was comming because i havent given any flag so compiler going to neglet that much portion of code & i was getting warning.

gcc -Wall -c -LITTLE filename.c 

works perfectly...