Submitter: UK C Panel
Submission Date: 2005-03-04
Source: Joseph Myers
<joseph@codesourcery.com>
Reference Document: ISO/IEC
WG14 N1105
Version: 1.3
Date: 2006-04-04
Subject: Function definitions with empty
parentheses
Summary
I believe the intent of C is that old-style function definitions with empty parentheses do not give the function a type including a prototype for the rest of the translation unit. For example,
void f(){}
void g(){if(0)f(1);}
is valid.
6.9.1#7 specifies that if the declarator in the function definition includes a parameter type list, it also serves as a prototype for the rest of the translation unit. It does not specify that nothing else serves as a prototype. Some readers of the standard interpret 6.7.5.3#14, "An empty list in a function declarator that is part of a definition of that function specifies that the function has no parameters.", as specifying that it provides a prototype.
Question 1: Does such a function definition give the function a type including a prototype for the rest of the translation unit?
Question 2: Is the above translation unit valid?
Suggested Technical Corrigendum
Committee Response
The grammar states that an empty parens stands for an empty identifier list not an empty parameter-type-list.
The answer to question #1 is NO, and to question #2 is YES. There are no constraint violations, however, if the function call were executed it would have undefined behavior. See 6.5.2.2;p6.