Asterisk space in C - What does the additional white space mean?

Question

I think that *something and * something are different.

What does the additional white space do?

occurs here -> void * malloc( size_t number_bytes );

An asterisk with a space...? You need to be more specific. Where is this occurring? What are you doing in your code? — BoltClock, Aug 10 '10 at 19:28
What!? Are you talking about difference between `char* someWord` and `char *someWord` (in which case, there is none)? — Justin Niessner, Aug 10 '10 at 19:28
It is an indication that you should probably consult [a good introductory book on C](http://stackoverflow.com/questions/562303/the-definitive-c-book-guide-and-list). — James McNellis, Aug 10 '10 at 19:31
This is a newbie question, but to be fair, the "declaration reflects use" convention in C for pointers and dereference operators is quite confusing when you first learn it. I don't think the down votes were justified. — A. Levy, Aug 10 '10 at 19:51
possible duplicate of [In C, why is the asterisk before the variable name, rather than after the type?](http://stackoverflow.com/questions/398395/), [What's your preferred pointer declaration style, and why?](http://stackoverflow.com/questions/377164/) — outis, Dec 20 '11 at 22:41

score 13 · Accepted Answer · answered Aug 10 '10 at 19:37

13

int* foo == int *foo == int * foo == int  *   foo

The whitespace does not make any difference to the compiler.

answered Aug 10 '10 at 19:37

Justin Ardini

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this is what I call a true example – Delirium tremens Aug 10 '10 at 19:43
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I didn't downvote, but given this is a noob question, you may want to avoid the use of `==` in that context as it is not valid syntax and could confuse learners. – bstpierre Aug 11 '10 at 02:32

Mark Byers · Answer 2 · 2010-08-10T19:46:27.180

When you use an asterisk to get the value of an address it is called the dereference operator. For example:

int x = *something;

In the example in your question the asterisk has a different meaning because it is part of a type, not part of an expression. It is used to specify that the return type is a pointer (in your specific example, a void pointer).

The extra space does not mean anything and is ignored by the compiler. It is there only to aid readability.

score 2 · Answer 3 · answered Aug 10 '10 at 21:11

The * operator in a declaration always binds to the declarator; the line

void * malloc (size_t number_bytes);

is parsed as though it had been written

void (*malloc(size_t number_bytes));

It's an accident of C syntax that you can write T *p; or T* p; or even

T             *                     p;

but all of them are parsed as T (*p); -- the whitespace makes no difference in how the declarations are interpreted.

score 1 · Answer 4 · answered Aug 10 '10 at 19:29

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C ignores extraneous whitespace, so "* " should have the same effect as "*".

If you want more clarification, please post a code example.

answered Aug 10 '10 at 19:29

Justin Ethier

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score 0 · Answer 5 · answered Aug 10 '10 at 19:28

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The same thing, but with some whitespace added.

answered Aug 10 '10 at 19:28

Mike Caron

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score 0 · Answer 6 · answered Aug 10 '10 at 19:29

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Check out this article on Pointers

Those two lines do the exact same thing.

answered Aug 10 '10 at 19:29

Robert Greiner

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score 0 · Answer 7 · answered Aug 10 '10 at 19:36

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In your void * malloc(...) example, void * is the type. malloc returns a pointer to void, which is just a pointer that needs to be cast to a particular type in order to be useful.

answered Aug 10 '10 at 19:36

nmichaels

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Asterisk space in C - What does the additional white space mean?

7 Answers7