MISRA.INIT.SIZE.IMPLICIT.2012

A designated initializer is used to initialize an array object when the size of the array is not specified explicitly.

MISRA C 2012 Rule 9.5: Where designated initializers are used t o initialize an array object the size of the array shall be specified explicitly

Category: Required

Analysis: Decidable, Single Translation Unit

Applies to: C99

Amplification

The rule applies equally to an array subobject that is a flexible array member.

Rationale

If the size of an array is not specified explicitly, it is determined by the highest index of any of the elements that are initialized. When using designated initializers it may not always be clear which initializer has the highest index, especially when the initializer contains a large number of elements.

To make the intent clear, the array size shall be declared explicitly. This provides some protection if, during development of the program, the indices of the initialized elements are changed as it is a constraint violation to initialize an element outside the bounds of an array.

Example

/* Non-compliant - probably unint entional to have single element */ 
int a1[ ] = { [ 0 ] = 1 };

/* Compliant                                                      */ 
int a2[ 10 ] = { [ 0 ] = 1 };