On Mon, Oct 8, 2012 at 6:42 AM, Dirk Eddelbuettel <[email protected]> wrote:
>
> Hi Ben,
>
> On 8 October 2012 at 10:24, North, Ben wrote:
> | Hi,
> |
> | I've been using Rcpp for a while now, and finding it very useful ---
> | thanks!
> |
> | Recently, though, I came across strange behaviour when running under
> | gctorture(TRUE) and C++ exceptions were being forwarded to R. The error
> | message string at the R level was some essentially random pathname, and
> | the string in the C++ exception was nowhere to be seen. The classname
> | at the R level was the logical TRUE value.
> |
> | The patch below fixed the problem for me. I would not claim to fully
> | know what I'm doing, so perhaps somebody who does could review and then
> | make the proper fix :-)
>
> It's been a while since we had something like this, and Doug lead it the last
> time. From what I recall, Rf_install() is safe, and the reason we factor
> these out as below. The bad boy, as I call, is probably Rf_mkString so by
> just doing
>
> str_what = Rf_install(exception_what.c_str());
> str_class = Rf_install(exception_class.c_str());
> str_ns = Rf_install("Rcpp"));
> Rf_eval(Rf_lang3(cppExceptSym, str_what, str_class), str_ns);
>
> may be enough. Could you test that?
Just glancing quickly at this, I think it may or may not work.
Rf_install looks up a symbol in the symbol table, installing it if
needed, and returns the symbol SEXP. Rf_mkstring creates a string
SEXP (vector of R class "character" containing a single string). The
string probably needs protection. The symbol does not.
I imagine the R function cpp_exception expects strings. I'm not sure
what happens if it gets symbols.
> |
> | Thanks,
> |
> | Ben.
> |
> | --- src/exceptions.cpp 2012-10-01 01:29:53.000000000 +0100
> | +++ ../Rcpp/src/exceptions.cpp 2012-10-08 11:14:39.435644100 +0100
> | @@ -161,14 +161,23 @@
> | exception_class = name ; /* just using the mangled name */
> | }
> | }
> | - SEXP cppExceptSym = Rf_install("cpp_exception"); // cannot cause a
> gc() once in symbol table
> | - Rf_eval(
> | - Rf_lang3(
> | - cppExceptSym,
> | - Rf_mkString(exception_what.c_str()),
> | - Rf_mkString(exception_class.c_str())
> | - ), R_FindNamespace(Rf_mkString("Rcpp"))
> | - ) ;
> | +
> | + SEXP cppExceptSym;
> | + SEXP str_what, str_class, str_ns, ns, expr;
> | +
> | + PROTECT(cppExceptSym = Rf_install("cpp_exception"));
> | + PROTECT(str_what = Rf_mkString(exception_what.c_str()));
> | + PROTECT(str_class = Rf_mkString(exception_class.c_str()));
> | + PROTECT(str_ns = Rf_mkString("Rcpp"));
> | +
> | + PROTECT(ns = R_FindNamespace(str_ns));
> | + PROTECT(expr = Rf_lang3(cppExceptSym, str_what, str_class));
> | +
> | + Rf_eval(expr, ns); /* Should not return. */
> | +
> | + // Do this in case somehow someone replaces the definition of
> | + // "cpp_exception" such that it does return:
> | + UNPROTECT(6);
> | }
> | #else
> |
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> --
> Dirk Eddelbuettel | [email protected] | http://dirk.eddelbuettel.com
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