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Re: on confusing procedure names with the address of procedures

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On 10/29/21 11:32 PM, Manfred wrote:
...
> In expressions where the function name is used (but not as a call to 
> that function, so not main()), the function is automatically converted 
> to a pointer to function (similar to arrays that decay to pointers in 
> many circumstances).

The rule you're referring to is "A function designator is an expression
that has function type. Except when it is the operand of the sizeof
operator, 69) or the unary & operator, a function designator with type
"function returning type" is converted to an expression that has type
"pointer to function returning type"." (6.3.2.1p4).
The "69)" refers to footnote 69, which points out that "Because this
conversion does not occur, the operand of the sizeof operator remains a
function designator and violates the constraints in 6.5.3.4."

Note that the only exceptions to that rule are for sizeof and &; there
is no exception to that rule for actual function calls. That's good,
because the standard imposes a constraint: "The expression that denotes
the called function 102) shall have type pointer to function returning
void or returning a complete object type other than an array type."
(6.5.5.2p1). If it weren't for that automatic conversion, a call to main
would require the following syntax: "(&main)()".

Note that this is a change that occurred in C90. K&R C had no such
conversion, and specified that "A function call is a primary expression
followed by parentheses ... The primary expression must be of type
"function returning ...""
The conversion and the constraint were both introduced when C was first
standardized, so that main() remained a valid function call, albeit for
different reasons, both in K&R C and in C90.

The purpose of the change was to simplify the use of function pointers.
Before the change, they had to be called using (*function_pointer)().
That remains a valid expression, since *function_pointer is an
expression of function type, which automatically gets converted back to
a pointer, but they can now also be called more directly by using
function_pointer().

...
>    void (*foo)() = bar;
> 
>    // You can execute the call in both of the following ways:
> 
>    foo(); // the pointer is implicitly dereferenced

That hasn't been true since C90.

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on confusing procedure names with the address of procedures Meredith Montgomery <mmontgomery@levado.to> - 2021-10-29 21:37 -0300
  Re: on confusing procedure names with the address of procedures Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-29 18:29 -0700
  Re: on confusing procedure names with the address of procedures Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-29 18:33 -0700
  Re: on confusing procedure names with the address of procedures Manfred <noname@add.invalid> - 2021-10-30 05:32 +0200
    Re: on confusing procedure names with the address of procedures James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-30 01:26 -0400
      Re: on confusing procedure names with the address of procedures Manfred <noname@add.invalid> - 2021-10-30 19:05 +0200
        Re: on confusing procedure names with the address of procedures James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-30 15:17 -0400
  Re: on confusing procedure names with the address of procedures Bart <bc@freeuk.com> - 2021-10-30 11:36 +0100
  Re: on confusing procedure names with the address of procedures Noob <root@127.0.0.1> - 2021-11-01 13:03 +0100

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