🚀 go-pugleaf

alan@elroy.Jpl.Nasa.Gov (Alan S. Mazer) writes:

>In article <1993Jan23.042626.991@verdix.com> scotty@verdix.com (Scott R. Chilcote) writes:
>> 
>>We're programming a device that has a RAM cache at address 809800H.
>>Is it legal to address this memory in C as follows?
>>#define ON_CHIP 0x809800
>>...
>>   float *oc_ptr = (float *) ON_CHIP;

>Excuse me, but the replies to this are getting silly.  The poster doesn't
>have an int.  He has an integer constant.  ...
>There is simply an assignment.  What he's proposing is fine.

Sorry, no.

A literal hexadecimal integer constant has type int or long, signed or
unsigned, depending on its value and the ranges of those types.
Assuming the value 0x809800 can be represented as type XINT, where XINT
is one of the above types, the code has the same effect as
	XINT i = ON_CHIP;
	float *oc_ptr = (float *) i;

In all such cases, an integer *value* is being cast to a pointer type.
There are no literal pointer constants (except the null pointer) in C.
The results of casting an integer value to a pointer type are
implementation-defined and not portable.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com