In the odesolve routine lsoda(), I allow the function (named func) that calculates the
system of differential equations to be defined in a dll that has been dynamically
loaded from the file named in dllname. I use getNativeSymbolInfo(func,
dllname)$address to get the address of the function and pass it to a C function
called via the .Call interface. Inside that C function, I use
R_ExternalPtrAddr(deriv_func) to get the function pointer. This requires typcasting
the return value of R_ExternalPtrAddr from (void *) to (deriv_func *), defined in a
typedef in call_lsoda().
To be more explicit (I'm replacing irrelevant arguments with ellipses):
In lsoda(...,func,dllname,...), func contains a string giving the name of a function
which is defined in the dll whose name is contained in dllname.
inside lsoda() are lines like
func <- getNativeSymbolInfo(symbol.C(func),PACKAGE=dllname)
.Call("call_lsoda",...,func)
inside call_lsoda.c are the lines:
SEXP func;
typedef void deriv_func(long int *, double *,double *, double *);
derivs = (deriv_func *) R_ExternalPtrAddr(func);
This all worked up to now, but now, (as Kurt Hornik kindly informs me) gcc 3.4 gives
the warning:
warning: ISO C forbids conversion of object pointer to function pointer type
so I need to clean this up so odesolve will compile cleanly for version 2.0.0 of R.
I'm at a loss of what to do, though, since the return value of R_ExternalPtrAddr is
(void *), and I need a function pointer.
I'd guess there would need to be a special function (say declared as
( R_ExternalFnPtr(SEXP s) *)(),
or something like that), to make all this work, but I can't find such a function. My
C programming is pretty rusty, so I'm wondering if someone has an idea about how I can
get around this problem (or perhaps I've misunderstood the meaning of the error
message? )
Woody Setzer
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