I have an example code:
#include <quadmath.h>
int main()
{
__float128 foo=123;
cosq(foo);
return 0;
}
I tried to compile it with the following commands:
g++ f128.cpp -lquadmath
g++ f128.cpp /usr/lib64/gcc/x86_64-suse-linux/4.6/libquadmath.a
g++ f128.cpp /usr/lib64/gcc/x86_64-suse-linux/4.6/libquadmath.a /usr/lib64/libquadmath.so.0
g++ f128.cpp /usr/lib64/gcc/x86_64-suse-linux/4.6/libquadmath.a /usr/lib64/libquadmath.so.0 /usr/lib64/gcc/x86_64-suse-linux/4.6/libquadmath.a
All these commands produce one and the same error:
f128.cpp:(.text+0x1b): undefined reference to `cosq(__float128)'
I also tried to declare cosq as follows, without inluding quadmath.h. Declarations of such style are used in C++ interface to fortran subroutines in other programs, and they work well.
extern "C" __float128 cosq_(__float128 *op);
extern "C" __float128 cosq_(__float128 op);
extern "C" __float128 cosq(__float128 *op);
...and so on...
Result was the same.
Then I tried to use cosq in Fortran:
PROGRAM test
REAL*16 foo
REAL*16 res
foo=1;
res=cos(foo)
PRINT *,res
END
This program compiles and executes well (prints the answer with lots of digits), so cosq works in it. This program was compiled with no options: gfortran f128.f90.
I tried OpenSUSE 12.1 with gcc 4.6.2 and OpenSUSE 12.2 with gcc 4.7.1. *.h, *.a and *.so files mentioned are provided by gcc46-fortran and libquadmath46 packages.
All needed include files and libraries exist, linker doesn’t print any nonexistance errors.
What is the proper way to use cosq and other quadmath functions in C++?
I wouldn’t like to write Fortran wrappers for them.