Defect Report #157

Submission Date: 16 Oct 95
Submittor: BSI
Source: Clive D.W. Feather
Submitted to BSI by Clive D.W. Feather
In this Defect Report, identifiers lexically identical to those declared in standard headers refer to the identifiers declared in those standard headers, whether or not the header is explicitly mentioned.
This Defect Report has been prepared with considerable help from Mark Brader, Jutta Degener, Ronald Guilmette, and a person whose employment conditions require anonymity. However, except where stated, opinions expressed or implied should not be assumed to be those of any person other than myself.
Defect Report UK 005: Legitimacy of type synonyms
The C Standard does not clearly indicate when the spelling of a type name is or is not significant; in other words, when a type name may be replaced by another type name representing the same type.
Part 1
Subclause reads in part:
The special case of void as the only item in the list specifies that the function has no parameters.
Subclause 6.7.1 reads in part:
(except in the special case of a parameter list consisting of a single parameter of type void, in which there shall not be an identifier).
In both cases, the word void is set in the typeface used to indicate C code.
In the code:
typedef void Void;
extern int f (Void);
int f (Void) { return 0; }

is the declaration on line 2 strictly conforming, and is the external definition on line 3 strictly conforming?
Part 2
Subclause reads in part: It can be defined with no parameters:

int main (void) { /* ... */ }
Is the following definition of main strictly conforming?
typedef int word;
word main (void) { /*
... */ }

Part 3
Are there any circumstances in which a typedef name is not permitted instead of the type it is a synonym for? If so, what are they?
Proposed Response
A synonym is always acceptable, except that a function definition may not use a typedef for the function type.
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