When are Parentheses Allowed in Variable Declarations in C ?

Variable Declaration with Parentheses in C Standard

In the realm of C programming, the # Which part of the C standard allow to declare variable in parenthesis? question arises, leaving many programmers mystified. This article sheds light on this puzzling syntax by examining the depths of the C standard and unfolding the hidden logic.

The C standard elucidates this intriguing behavior in [dcl.meaning]. According to this section, a declaration of the form T D, where D takes the form ( D1 ), retains the type of the declarator-id in the contained declaration T D1. Crucially, parentheses do not alter the type of the encapsulated declarator-id but may influence the binding of complex declarators.

In essence, you may enclose any "declarator" in parentheses as per the C grammar. Broadly speaking, a declarator is a component of a declaration that excludes initial specifiers and types and encapsulates a single name.

Take the provided example: int(s). Here, s represents a declarator. Hence, enclosing it in parentheses does not alter its meaning or substance.

This rule holds special significance in more intricate scenarios. For instance, consider the following:

int * a [10]; // a is an array of ten pointers to int.
int ( * b ) [10]; // b is a pointer to an array of ten ints.

Here, parentheses play a vital role in differentiating between the two declarations. Without them, you might erroneously interpret b as an array of ten pointers to int, but the parentheses clarify that b is, in fact, a pointer to an array of ten int values.

In conclusion, the C standard accommodates variable declarations within parentheses, enabling programmers to navigate complex declarator bindings and maintain code clarity.

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