Thread: Old style fuction declarations

Originally Posted by c99

6.11.4 Function declarators
The use of function declarators with empty parentheses (not prototype-format parameter
type declarators) is an obsolescent feature.

6.11.5 Function definitions
The use of function definitions with separate parameter identifier and declaration lists
(not prototype-format parameter type and identifier declarators) is an obsolescent feature.

Code:

/* Old style function declarator */
void foo();

/* Old style function definition */
void foo()
  int a;
{
  /* do stuff */
}

In particular, there were NO checks on calling foo().
You could do
foo();
foo(123);
foo("I'm a banana");
without any compile time consequence.




As the standard says, these are obsolete syntax.

You should be doing

Code:

void foo(int a);

void foo(int a) {
  /* do stuff */
}

Being Dutch I have a continuous problem with IT explanations written in English.

At the top of a program, right underneath the "includes", are they "declarations"?
The first line of a function, is that the definition?
Then what is old style and what is new at the top of the program = declarations I presume?
Please a simple answer.

Forget about the old style, just use a function prototype and a function definition.

The old style has some odd terminology, which you're not understanding, and you don't need to worry about.

And no, writing it in a "dumbed down" colloquial English will only serve to confuse further by overloading different specific meanings onto one general term.

Code:

// This is a prototype, it has the parameter types already listed.
void foo(int a);
 
// This is a definition, it matches the prototype.
void foo(int a) {
  /* do stuff */
}

Zeus_, that's for C++. This is the C programming forum.