any evaluatable subexpression to be accepted as an integer constant
expression.</li>
<li><b><tt>__builtin_constant_p</tt></b>: This returns true (as a integer
- constant expression) if the operand is any evaluatable constant. As a
+ constant expression) if the operand evaluates to either a numeric value
+ (that is, not a pointer cast to integral type) of integral, enumeration,
+ floating or complex type, or if it evaluates to the address of the first
+ character of a string literal (possibly cast to some other type). As a
special case, if <tt>__builtin_constant_p</tt> is the (potentially
parenthesized) condition of a conditional operator expression ("?:"), only
the true side of the conditional operator is considered, and it is evaluated
floating-point literal.</li>
<li><b><tt>__builtin_abs,copysign,..</tt></b>: These are constant folded as
general constant expressions.</li>
-<li><b><tt>__builtin_strlen</tt></b> and <b><tt>strlen</tt></b>: These are constant folded as integer constant expressions if the argument is a string literal.</li>
+<li><b><tt>__builtin_strlen</tt></b> and <b><tt>strlen</tt></b>: These are
+ constant folded as integer constant expressions if the argument is a string
+ literal.</li>
</ul>