Defect Report #119

Submission Daee: 03 Dec 93
Submittor: WG14
Source: Ron Guilmette
Question
ANSI/ISO C Defect Report #rfg26:
Subject: Initialization of multi-dimensional array objects.
a) Is a diagnostic required for the following declaration?
b) Is the following declaration strictly conforming or not?
static int array[][] = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
Background:
Subclause 6.5.7 (Semantics):

If an array of unknown size is initialized, its size is determined by the number of initializers provided for its elements.

Subclause 6.5.7 (Semantics):

If the aggregate contains members that are aggregates or unions, or if the first member of a union is an aggregate or union, the rules apply recursively to the subaggregates or contained unions.

On the basis of the above quoted rules, one might conclude that the code example given above is strictly conforming. (Many existing implementations seem to disagree, however.)
Response
a) No, a diagnostic is not required. It is a semantic requirement that array elements must be objects, not a constraint.
b) No, this is undefined behavior. Note that array does not have an array type because its element type is not an object type; hence subclause 6.5.7 does not apply. See subclause 6.1.2.5.
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