On 6 June 2009 at 17:03, Kynn Jones wrote:
| Consider the following simple C program:
|
| /*** hello_r.c ***/
| #include <Rinternals.h>
|
| SEXP hello() {
| return mkString("Hello, world!\n");
| }
|
| int main(void) {
| SEXP x = hello();
| return x == NULL; /* i.e. 0 on success */
| }
|
| This program segfaults:
|
| % myR/bin/R CMD LINK gcc -I./R-2.9.0/src/include -L./myR/lib64/R/lib -lR
| hello_r.c -o hello_r > /dev/null
| % hello_r
| zsh: segmentation fault hello_r
The error is in your assumption that because the code below works, the code
above should as well. That is wrong -- there is more to embedding R than you
do here.
| But if instead of compiling the program as a standalone I make it as a
| shared library, like this:
|
| % myR/bin/R CMD SHLIB --preclean hello_r.c > /dev/null
|
| ... then the hello() function works fine, when run from within an R session:
|
| > dyn.load(paste("hello_r", .Platform$dynlib.ext, sep = ""))
| > .Call("hello")
| [1] "Hello, world!\n"
|
|
| The fact that the same function succeeds when run from within an R session
| but segfaults when run from the standalone executable tells me that, in the
| standalone case, the main() function needs to do some initialization stuff
| on R before one can invoke functions like mkString(), but I have not been
| able to find what this initialization should be.
| If someone could point me in the right direction I'd appreciate it.
Try reading 'R Extensions' section 8.1 entitled 'Embedding R under
Unix-alikes'.
Or you use something like my 'RInside' classes (on r-forge and my website) to
more easily embed R into C++ programs.
| Also, where is the documentation for the call_R function? It is mentioned
| several times in the Writing R Extensions document, but I have not been able
| to find the documentation for it.
I think that's a C level function in the R sources, so you may have to look
there:
e...@ron:~> grep -rin call_R src/debian/R/R-2.9.0/src/
src/debian/R/R-2.9.0/src/library/base/man/Foreign.Rd:150: \R functions can be
invoked using \code{call_S} or \code{call_R} and
src/debian/R/R-2.9.0/src/library/base/man/Foreign.Rd:170:
\code{call_S}/\code{call_R}. New code using \R objects should be
src/debian/R/R-2.9.0/src/main/dotcode.c:2409:void call_R(char *func, long
nargs, void **arguments, char **modes,
src/debian/R/R-2.9.0/src/main/dotcode.c:2417: error(_("invalid function in
call_R"));
src/debian/R/R-2.9.0/src/main/dotcode.c:2419: error(_("invalid argument count
in call_R"));
src/debian/R/R-2.9.0/src/main/dotcode.c:2421: error(_("invalid return value
count in call_R"));
src/debian/R/R-2.9.0/src/main/dotcode.c:2464: error(_("mode '%s' is not
supported in call_R"), modes[i]);
src/debian/R/R-2.9.0/src/main/dotcode.c:2506: call_R(func, nargs, arguments,
modes, lengths, names, nres, results);
src/debian/R/R-2.9.0/src/main/coerce.c:1317: errorcall_return(call,
R_MSG_mode);
src/debian/R/R-2.9.0/src/main/coerce.c:1363: errorcall_return(call,
R_MSG_mode);
src/debian/R/R-2.9.0/src/main/coerce.c:1769: errorcall_return(call,
R_MSG_mode);
src/debian/R/R-2.9.0/src/main/coerce.c:1812: errorcall_return(call, "is.na "
R_MSG_list_vec);
src/debian/R/R-2.9.0/src/main/coerce.c:1924: errorcall_return(call, "is.nan
" R_MSG_list_vec);
src/debian/R/R-2.9.0/src/main/coerce.c:2019: errorcall_return(call,
"is.finite " R_MSG_list_vec);
src/debian/R/R-2.9.0/src/main/coerce.c:2071: errorcall_return(call,
"is.infinite " R_MSG_list_vec);
src/debian/R/R-2.9.0/src/main/coerce.c:2128: errorcall_return(call,
R_MSG_A1_char);
src/debian/R/R-2.9.0/src/main/complex.c:917: errorcall_return(call,
_("unimplemented complex function"));
src/debian/R/R-2.9.0/src/main/builtin.c:142: errorcall_return(call,
_("invalid number of arguments"));
src/debian/R/R-2.9.0/src/include/Rinternals.h:652:#define
errorcall_return(cl,msg){ Rf_errorcall(cl, msg); return R_NilValue; }
src/debian/R/R-2.9.0/src/include/S.h:73:/* void call_R(char*, long, void**,
char**, long*, char**, long, char**);*/
src/debian/R/R-2.9.0/src/include/S.h:74:#define call_S call_R
src/debian/R/R-2.9.0/src/include/R_ext/RS.h:86:void call_R(char*, long,
void**, char**, long*, char**, long, char**);
Hth, Dirk
--
Three out of two people have difficulties with fractions.
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