I am using C++ Builder 5 to develop windows GUI interface for a R library package. I have to pass R objects to and from C functions and also evaluate them within C functions. But I always got linking error message of "unresolved external functions" with those internal functions or macros defined in Rinternals.h file. I can not find the reason.
There are many possible reasons - you didn't say anything about how you exactly access the DLL, create the R.lib etc. All I can do is to imagine what you did wrong, so I hope this will cover some of it.
There are following pitfalls I can think of (I omitted obvious ones like include paths and run-time issues like determining R_HOME etc.)
1) You should globally define Win32 in your project - depending on the BCC you use this may not be the default, and R relies on it
2) C vs C++:
I assume that you'll be using C++ (otherwise there's no need for C++ Builder ;)). R.dll exports are all in C language, most of them are also in the C calling convention. You must be aware of this when interfacing externals. Note that there are several includes that you need to wrap in export "C" { ... }!
If you see symbol "R_xxx" not defined then you have this C vs. C++ problem. If something else is wrong you should see symbol "_R_xxx" not defined - that's in fact an improvement!
3) R.DEF
BCC and gcc disagree about the notations in the DEF file. I assume that you won't use any STDCALL functions of R (it's just some bz2 func etc.), so I'll skip that issue.
BCC is looking for the exports of the form _function - so you need to modify the R.DEF supplied with R in order to be usable with BCC. You need to do two things:
- remove all hints (the @nnn at the end of all lines)
- mangle all function names, i.e. the line:
R_DefParams @215
should become:
_R_DefParams=R_DefParams
This can be easily done by a simple script.
4) generate a R.lib with implib -c R R.def
Now you're ready to use R.dll in your program. But before you plunge into writing some Win apps that interface to R, you should definitely look at other projects that use R.dll - there is a lot of issues you should be aware of, especially involving the initialization of R (Win32 version has no Rf_initEmbeddedR).
Cheers, Simon
--- Simon Urbanek Department of computer oriented statistics and data analysis Universit�tsstr. 14 86135 Augsburg Germany
Tel: +49-821-598-2236 Fax: +49-821-598-2280
[EMAIL PROTECTED] http://simon.urbanek.info
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