Calling the original function after tweaking arguments is an incorrect use of the R-API?

Hi,

I am trying to create a small extension for R here for embedding the
current time on the R prompt:https://github.com/musically-ut/extPrompt

Things seem to be working overall, but R CMD check . raised a warning:

File '[truncated]..Rcheck/extPrompt/libs/extPrompt.so?: Found non-API call

to R: ?ptr_R_ReadConsole?

Compiled code should not call non-API entry points in R.


The concerned file is this:
https://github.com/musically-ut/extPrompt/blob/master/src/extPrompt.c and
occurs on line 38, I think.

void extPrompt() {

    // Initialize the plugin by replacing the R_ReadConsole function
    old_R_ReadConsole = ptr_R_ReadConsole;
    ptr_R_ReadConsole = extPrompt_ReadConsole;
    // ...
}
int extPrompt_ReadConsole(const char *old_prompt, unsigned char *buf, int
len,
         int addtohistory) {
    // ...
    // Call the old function with the `new_prompt`
    return (*old_R_ReadConsole)(new_prompt, buf, len, addtohistory);
}

I am trying to make the R_ReadConsole API call. However, since a different
plugin (like mine) could have overridden it already, I do not want to
directly invoke R_ReadConsole but the function which previously was at
ptr_R_ReadConsole.

Is this an incorrect use of the API?

Also, any other feedback on the plugin is also welcome.

Thanks.

~
ut

PS: I had posted this question on StackOverflow a while back:
http://stackoverflow.com/questions/26335571/is-this-an-incorrect-use-of-the-r-api
If I receive a response, I will update the question with the appropriate
answer.