c - Which is the better way to declare dummy variables for nested loops?

1. The advantage of approach 1 is a slightly smaller file size due to less text characters in the source code:

   
   
   
   

   int i, j;
   for (i = 0; i < numRows; i++)
       for (j = 0; j < numCols; j++)
       //
   




2. The advantage of approach 2 is the smaller scope of local variables.

   
   
   

   int i;
   for (i = 0; i < numRows; i++)
   {
   
       int j;
       for (j = 0; j < numCols; j++)
       //
   }
   

Even if the differences in optimizations are negligible in today's modern computers, which approach is considered "better" code?

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Edit to clarify that this question is not a duplicate:

This question is based on the current C11 standard, which does not allow for syntax like this:

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

In C++ and C99, this syntax is perfectly acceptable whereas C11 does not allow for variable declarations inside the for statement.

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Edit to correct misinformation:

I thought I was using C11 because I had recently downloaded the compiler from CodeBlocks, so that's why I said C11 didn't allow for variable declarations inside the for statement. But it turns out I was actually using C90, which was the root of my problems.

Answer

For sheer compactness and limiting of scope, I would use:

for (size_t i = 0; i < numRows; i++) {
    for (size_t j = 0; j < numCols; j++) {

    //
    }
}

Note the use of size_t for what appear to be array indices. The size_t type is an unsigned integer type guaranteed to be able to hold any array index. Just a matter of style, but I would also suggest using braces around all loop bodies. This makes it much less likely that you will break your code with inevitable updates and changes.

By making it a habit to declare loop variables with block scope like this, you force yourself to choose to use the values stored in loop variables elsewhere in your code.