OpenEuphoria

Re: Pass C double to Eu shared library

• Posted by mattlewis (admin) May 12, 2012
• 1545 views

Euphoria shared dynamically loading library can also be used by C programs as long as only 31-bit integer values are exchanged.  
If a 32-bit pointer or integer must be passed, and you have the source to the C program, you could pass the value in  
two separate 16-bit integer arguments (upper 16 bits and lower 16 bits), and then combine the values in the Euphoria  
routine into the desired 32-bit atom.  

-- Eu Code 
export function MyFunc(sequence x) 
  ? x 
end function 

// C Code 
extern MyFunc(double x[]) 
 
int main() { 
double x[4] = {1.1,2.2,3.3,4.4}; 
MyFunc(x); 
return 0; 
} 

I think the cleanest way is to use Use 32-bit Integers In Translated DLLs. It's kind of a hack, but I think it's the cleanest solution. It requires special wrappers that the external world should call, and it modifies your translated source.

It seems to almost work with 4.0.4. This required some updates to make_atom.exw for 4.0. And I modified test.exw to open the .so that I created on Linux, instead of a Windows dll.

$ euc -makefile -so test.ew 
Translating code, pass: 1 2 3  generating 
 
4.c files were created. 
To build your project, type make -f test.mak 
 
$ eui make_atom.exw 
~/eu/32bits$ make -f test.mak                                                                                                                                     
gcc -fomit-frame-pointer -fPIC -c -w -fsigned-char -O2 -m64 -I/usr/local/share/euphoria -ffast-math init-.c -o init-.o                                                         
gcc -fomit-frame-pointer -fPIC -c -w -fsigned-char -O2 -m64 -I/usr/local/share/euphoria -ffast-math test.c -o test.o                                                           
gcc -fomit-frame-pointer -fPIC -c -w -fsigned-char -O2 -m64 -I/usr/local/share/euphoria -ffast-math main-.c -o main-.o                                                         
gcc -fomit-frame-pointer -fPIC -c -w -fsigned-char -O2 -m64 -I/usr/local/share/euphoria -ffast-math make_atom.c -o make_atom.o                                                 
gcc -o test.so init-.o test.o main-.o make_atom.o  /usr/local/lib/euso.a -m64 -shared  -ldl -lm -lpthread                                                 
 
$ eui test 
Passing signed integer: -225 
Signed( -225 ) 
 
Passing unsigned integer: 4294967071 
Unsigned( 4294967071 ) 
 
Done.  Press any key to exit. 

Matt