Old style fuction declarations

When I look up on the Net, what old and new style function declarations look like, I get a whole lot gibberdejab. Please give me a simple example of an old, and a new style function declaration, showing the difference, so I might learn what one should and shouldn't do. Thank you, Zach K.

Quote:

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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.

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Code:

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

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

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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:

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void foo(int a);

void foo(int a) {
  /* do stuff */
}

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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.

A complete example with *only* but *all* the relevant lines often is *much* more informative than jargon text of which the reader might not understand all the words. This is my many years of teaching experience. I find many explanations on the Net totally bewildering.

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:

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// 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 */
}

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"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."

I am not talking about dunned down English!!

I am saying *stick to the principle involved* and down dress it up wit a lot of airy fairy talk. I am speaking in general. Not to you personally. You are a great help all the time.

I'm still reading through this but I really like the way many things are explained in it. Might be helpful to you...

C++ Core Guidelines

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

Quote:

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Originally Posted by zach

When I look up on the Net, what old and new style function declarations look like, I get a whole lot gibberdejab. Please give me a simple example of an old, and a new style function declaration, showing the difference, so I might learn what one should and shouldn't do. Thank you, Zach K.

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How about you read K&R . Note that first chapter is different from other chapters. I suppose both function declarations are discussed in the book.

Oh yeah, sorry! I forgot that I switched between the programming boards :redface: