Are Flexible Array Members Valid in C ?

Flexible Array Members in C

In C99, flexible array members can be used to declare arrays of unknown size as part of a structure. However, the validity of this feature in C has been a subject of confusion.

Validity in C

C was standardized in 1998, predating the introduction of flexible array members in C99. Consequently, flexible array members are not supported in C .

Correct Declaration

Despite the misconception, '[0]' is a valid declaration for a flexible array member in C . This syntax indicates that the size of the array is not specified and must be set by the user at runtime.

Example

In C , the following code will compile and execute without errors:

struct Blah {
    int foo[0];
};

In contrast, the syntax '[]' without a size is invalid in C . Attempting to declare a flexible array member using this syntax will result in a compiler error.

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