Submitter: UK C Panel
Submission Date: 2005-03-04
Source: Joseph Myers <joseph@codesourcery.com>
Reference Document: ISO/IEC WG14
N1099
Version: 1.0
Date: 2005-03-04
Subject: Definition of variably modified types
Summary
Variably modified types are defined by 6.7.5#3:
[#3] A full declarator is a declarator that is not part of another declarator. The end of a full declarator is a sequence point. If the nested sequence of declarators in a full declarator contains a variable length array type, the type specified by the full declarator is said to be variably modified.
It is desirable for the definition to look at the declarator rather than just the resulting type, so that function parameters adjusted from array to pointer type are variably modified if the array size is variable: in
void
f (int i, int a[static ++i])
{
// ...
}
the increment of i must be evaluated for the definition of static in
this context to make sense. However, what it means for the
declarators to "contain" a type is unclear. The natural
interpretation is that they include an array declarator with array
size [*] or an expression which is not an integer constant
expression. However, this does not cover cases such as
int x;
// ...
typedef int vla[x];
vla y[3];
where a typedef for a variably modified type is used. y is a VLA, and
clearly ought to be variably modified, but nothing about the
declarators makes it variably modified; only the declaration specifier
does so.
Suggested Technical Corrigendum