[Rd] How to customize the list of exported functions in a shared library

[Vladimir Eremeev]

Andrew Piskorski wrote:
> 
> On Mon, Feb 05, 2007 at 01:28:24AM -0800, Vladimir Eremeev wrote:
>> I am writing binding from C library to R.
>> I use R 2.4.1, windows XP, and MinGW.
> 
>> R CMD SHLIB -d --output=Rsnns.dll  [ list of all C sources]
> 
>> R CMD SHLIB -d --output Rsnns.dll Rsnns.c
>> -Wl,-Lc:/mingw/lib,-lfl,-L../sources,-lkernel,-lfunc
> 
> You should probably also show us the actual compiler/linker commands
> that "R CMD SHLIB" is generating, so we can be sure of what's really
> going on.
> 

It calls gcc:
gcc  "-I../sources" "-I."  -IC:/PROGRA~1/R/include  -gdwarf-2 -Wall -O2
-std=gnu99   -c rsnns.c -o rsnns.o
gcc  -shared   -o Rsnns.dll Rsnns.def [ lots of *.o ]  -LC:/PROGRA~1/R/bin
"-Lc:/mingw/lib" -lfl -liberty   -lR

The file Rsnns.def is generated automatically and is deleted on success.
On error, it remains, and contains export of all symbols.
Probably GCC generates it, I haven't tracked its generation in the R's
scripts.


Andrew Piskorski wrote:
> 
> I'm not sure what you may have to do differently with MinGW on Windows
> (what linker does that use anyway?), but for comparison, here's how I
> do it for R 2.2.1, on Linux (Ubuntu Dapper 6.06), with gcc 4.0.3, and
> Gnu ld 2.16.91:
> 

gcc.EXE (GCC) 3.4.2 (mingw-special)
GNU ld version 2.15.91 20040904

Thank you, I'll study this linker option.


Andrew Piskorski wrote:
> 
> For my own custom R package's C code, my Makefile says:
>   OBJ = ../foo.o $(patsubst %.c,%.o,$(wildcard ../source/[a-z]*.c))
>   $(OBJ): %.o:  %.c $(HDRS)
>   R.so: $(OBJ) Makevars vis.map
>           R CMD SHLIB -o my_pkg_name_R.so $(OBJ)
> 
> My Makevars includes this:
> 
>   PKG_LIBS = -Wl,--version-script=vis.map
> 
> And when I build my R package, the R.so make target above generates
> this link command:
> 
>   gcc -shared -o my_pkg_name_R.so [lots of *.o filenames here]
> -Wl,--version-script=vis.map -L/usr/lib/R/lib -lR
> 
> My vis.map file, which uses Gnu ld syntax, looks like this:
> 
>   {
>      global: my_pkg_*;
>      local:*;
>   };
> 
> That works, my shared library exports ONLY the symbols starting with
> "my_pkg_", everything else remains private.
> 
> It's the "--version-script" linker option doing the magic.  Even with
> Gnu ld, there are definitely other ways to control symbol visibility,
> but that one seemed most convenient in my case.
> -- 
> Andrew Piskorski <atp at piskorski.com>
> http://www.piskorski.com/
> 
> 

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