C: for loop int initial declaration
for (int i = 0; ...) is a syntax that was introduced in C99. In order to use it you must enable C99 mode by passing -std=c99 (or some later standard) to GCC. The C89 version is:
int i;for (i = 0; ...)EDIT
Historically, the C language always forced programmers to declare all the variables at the begin of a block. So something like:
{ printf("%d", 42); int c = 43; /* <--- compile time error */must be rewritten as:
{ int c = 43; printf("%d", 42);a block is defined as:
block := '{' declarations statements '}'C99, C++, C#, and Java allow declaration of variables anywhere in a block.
The real reason (guessing) is about allocating internal structures (like calculating stack size) ASAP while parsing the C source, without go for another compiler pass.
Before C99, you had to define the local variables at the start of a block. C99 imported the C++ feature that you can intermix local variable definitions with the instructions and you can define variables in the for and while control expressions.