Defect Report #095
Submission Date: 03 Dec 93
Source: Ron Guilmette
ANSI/ISO C Defect report #rfg2:
There is an ambiguity with respect to the constraints which may (or may
not) apply to initializations.
Subclause 6.5.7 says:
... the same type constraints and conversions as for simple
assignment apply, ...
Note however that this rule itself appears within a Semantics section,
thus leading some implementors to feel that no diagnostics are required
in cases where an attempt is made to provide an initializer for a
given scalar and where the type of the initializer is not assignment
compatible with the type of the scalar object being initialized. This
ambiguity should be removed by adding an explicit constraint to the
section covering initializations, such as:
Each scalar initializer expression given in an initializer shall
have a type such that its value may be assigned to an object with
the unqualified version of the corresponding scalar object to be initialized
by the given scalar initializer expression.
(This roughly mirrors the existing constraint on parameter matching
imposed upon calls to prototyped functions.)
An explicit constraint is not required in the initializer section.
Early on, the Committee decided that if a behavior was described as
being equivalent to another construct, all of the constraints of that
construct would apply. This ``chaining'' process means that
any violation of a constraint in any section referred to explicitly
or by the phrases ``equivalent behavior'' or ``as if''
will generate a diagnostic.
The constraints in the section on simple assignment
(subclause 22.214.171.124) are sufficient to assure type compatibility of
the object and the initializer.
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