R help - Nov 2009 - Unnecesary code?

Dear R-ers,

While browsing the R sources, I found the following piece of code 
in src\main\memory.c:

static void reset_pp_stack(void *data)
{
    R_size_t *poldpps = data;
    R_PPStackSize =  *poldpps;
}

To me, it looks like the poldpps pointer is a nuissance; can't you 
just cast the data pointer and derefer it at once? Say,

static void reset_pp_stack(void *data)
{
    R_PPStackSize = * (R_size_t *) data;
}

-- Hun

hunsyntesat at hush.com wrote:
> Dear R-ers,
>
> While browsing the R sources, I found the following piece of code 
> in src\main\memory.c:
>
> static void reset_pp_stack(void *data)
> {
>     R_size_t *poldpps = data;
>     R_PPStackSize =  *poldpps;
> }
>
> To me, it looks like the poldpps pointer is a nuissance; can't you 
> just cast the data pointer and derefer it at once? Say,
>
> static void reset_pp_stack(void *data)
> {
>     R_PPStackSize = * (R_size_t *) data;
> }
>   
What would you gain by this change?

Duncan Murdoch

On Thu, 19 Nov 2009 00:13:27 +0100 Duncan Murdoch 
<murdoch at stats.uwo.ca> wrote:
>hunsyntesat at hush.com wrote:
>> Dear R-ers,
>>
>> While browsing the R sources, I found the following piece of 
>code 
>> in src\main\memory.c:
>>
>> static void reset_pp_stack(void *data)
>> {
>>     R_size_t *poldpps = data;
>>     R_PPStackSize =  *poldpps;
>> }
>>
>> To me, it looks like the poldpps pointer is a nuissance; can't 
>you 
>> just cast the data pointer and derefer it at once? Say,
>>
>> static void reset_pp_stack(void *data)
>> {
>>     R_PPStackSize = * (R_size_t *) data;
>> }
>>   
>What would you gain by this change?
>
>Duncan Murdoch
Seriously? What would you gain by rejecting the change?

I think the gain is obvious, even if not essential: the code is 
cleaner. If there is a choice between two different pieces of code 
that have the same effect, choosing the simpler makes it easier to 
maintain the code, and easier for a casual user to understand 
what's going on. Anyone looking at the original code for the first 
time will have to realise that poldpps is a nuissance variable with 
no practical importance and no gain whatsoever, the change cuts 
this need.  

There is also a negligible loss in performance when the inessential 
stack variable is allocated.

-- Hun