R devel - Aug 2018 - longint

Hi

In my R package, imagine I have a C function defined:

 ?? void myfunc(int *x) {
 ????? // some code
 ?? }

but when I call it, I pass it a pointer to a longint instead of a 
pointer to an int. Could this practice potentially result in a segfault?

Regards
Ben

On 15/08/2018 7:08 AM, Benjamin Tyner wrote:
> Hi
> 
> In my R package, imagine I have a C function defined:
> 
>   ?? void myfunc(int *x) {
>   ????? // some code
>   ?? }
> 
> but when I call it, I pass it a pointer to a longint instead of a
> pointer to an int. Could this practice potentially result in a segfault?
I don't think the passing would cause a segfault, but "some code"
might
be expecting a positive number, and due to the type error you could pass 
in a positive longint and have it interpreted as a negative int.

Duncan Murdoch

> On 15 Aug 2018, at 12:48, Duncan Murdoch <murdoch.duncan at
gmail.com> wrote:
> 
>> On 15/08/2018 7:08 AM, Benjamin Tyner wrote:
>> Hi
>> In my R package, imagine I have a C function defined:
>>     void myfunc(int *x) {
>>        // some code
>>     }
>> but when I call it, I pass it a pointer to a longint instead of a
>> pointer to an int. Could this practice potentially result in a
segfault?
> 
> I don't think the passing would cause a segfault, but "some
code" might be expecting a positive number, and due to the type error you
could pass in a positive longint and have it interpreted as a negative int.
Are you thinking only of a little-endian system?  A 32-bit lookup of a pointer
to a 64-bit area could read the wrong half and get a completely different value.
> 
> Duncan Murdoch
> 
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