$ cat cppfunction.C
#include <cmath>
#include <mylib/mylib.hpp>
extern "C" 
{
    void cppfunction_(float *a, float *b);
}
void cppfunction_(float *a, float *b)
{
    *a = 7.0;
    *b = 9.0;
}
$ cat fprogram.f
program fprogram
real a, b
a = 1.0
b = 2.0
print*, "Before fortran function is called"
print*, 'a=', a
print*, 'b=', b
call cppfunction(a, b)
print*, "After cpp function is called"
print*, 'a=', a
print*, 'b=', b
stop
end

$ gfortran -c fprogram.f
$ g++ -c cppfunction.C
$ gfortran -lc -o fprogram fprogram.o cppfunction.o

cppfunction.o: In function `__static_initialization_and_destruction_0(int, int)':
cppfunction.C:(.text+0xa1): undefined reference to `std::ios_base::Init::Init()'
cppfunction.C:(.text+0xb0): undefined reference to `std::ios_base::Init::~Init()'
collect2: error: ld returned 1 exit status

<details>
<summary>英文:</summary>
I am trying to link a header only library (which is in cpp) to a fortran code. I am using [this example][1] to test my library.
       $ cat cppfunction.C
       #include&lt;cmath&gt;
       #include&lt;mylib/mylib.hpp&gt;
       extern &quot;C&quot; 
       {
        	void cppfunction_(float *a, float *b);
       }
       void cppfunction_(float *a, float *b)
       {
        	*a=7.0;
        	*b=9.0;
       }
      $ cat fprogram.f
       program fprogram
       real a,b
       a=1.0
       b=2.0
       print*,&quot;Before fortran function is called&quot;
       print*,&#39;a=&#39;,a
       print*,&#39;b=&#39;,b
       call cppfunction(a,b)
       print*,&quot;After cpp function is called&quot;
       print*,&#39;a=&#39;,a
       print*,&#39;b=&#39;,b
       stop
       end
For compiling I am using:
        $ gfortran -c fprogram.f
        $ g++ -c cppfunction.C
        $ gfortran -lc -o fprogram fprogram.o cppfunction.o
This runs fine if I remove my library header. But have this error when included:
        cppfunction.o: In function `__static_initialization_and_destruction_0(int, int)&#39;:
        cppfunction.C:(.text+0xa1): undefined reference to `std::ios_base::Init::Init()&#39;
        cppfunction.C:(.text+0xb0): undefined reference to `std::ios_base::Init::~Init()&#39;
        collect2: error: ld returned 1 exit status
Anything I might be doing wrong?
  [1]: https://www.cae.tntech.edu/help/programming/mixed_languages
</details>
# 答案1
**得分**: 0
你没有链接C++标准库：
gfortran -lc -lstdc++ -o fprogram fprogram.o cppfunction.o
//           ^^^^^^^^
<details>
<summary>英文:</summary>
You&#39;re not linking the C++ standard library:
    gfortran -lc -lstdc++ -o fprogram fprogram.o cppfunction.o
    //           ^^^^^^^^
</details>