Can someone suggest a book or online reference I could print out that gets
into the details of C99 (that's the version that microchip is based on =20
??) that this thread
and things like "ifndef" are covered. Microchip seems to leave out some=20
standard stuff, or I just haven't found where it's hiding.

On 8/11/2010 11:13 PM, Daniel Serpell wrote:
> Hi,
>
> On Wed, Aug 11, 2010 at 5:54 PM, peter green<plugwash@p10link.net>  wrote=
:
>   =20
>> Wouter van Ooijen wrote:
>>     =20
>>>   >  Afaict C varargs require the caller to do the removal
>>>
>>>       =20
>>>> because only the caller knows for sure how many parameters have been
>>>> passed and due to the retarted way C handles prototypes you can't have=
 a
>>>> different interface for varargs and non-varargs functions.
>>>>
>>>>         =20
>>> Maybe in super-ancient C, but with function prototypes...
>>>
>>>       =20
>> But when the compiler builds the function it doesn't know whether the
>> caller will be using function prototypes or not.
>>     =20
> The C99 standard explicitly requires that you have the prototype in the
> varargs case, see 6.5.2.2 paragraph 6:
>
>   If the expression that denotes the called function has a type that does
>   not include a prototype, the integer promotions are performed on each
>   argument, and arguments that have type float are promoted to double.
>   These are called the default argument promotions. If the number of
>   arguments does not agree with the number of parameters, the behavior is
>   undefined. If the function is defined with a type that includes a
>   prototype, and either the prototype ends with an ellipsis (, ...) or th=
e
>   types of the arguments after promotion are not compatible with the type=
s
>   of the parameters, the behavior is undefined.
>
> So, if you try to call a vararg function without providing the prototype,
> the result is undefined because you cannot define a vararg function
> without using a prototype, see 6.9.1 p8.
>
>      Daniel.
>
>   =20
--=20
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