FORTRAN passes null values to C

In many C or C + + header file definitions, NULL is specified to be defined as 0, which is no longer specifically expanded

Gfortran's Manual for the section on ISO c binding, define null as follows

Moreover, the following and named constants are defined:

Name	Type
C_NULL_PTR	C_PTR
C_NULL_FUNPTR	C_FUNPTR

Both is equivalent to the value in NULL C.

Thus, it is necessary to pass a null pointer from Fortran to C or C + +, which requires that the incoming parameter be set to the pointer type C_ptr

Next is the code:

#include"stdio.h"intTestint*a,intnum) {    if(!a) {printf ("This is null pointer\n"); }    Else{         for(intI=0; i<num; i++) {printf ("array[%d]=%d\n", i+1, A[i]); }    }    return 0;}

Program Mainuse, intrinsic:: iso_c_bindingImplicitNoneInterfaceinteger (c_int) function func (array, n) bind (c, name="Test") ImportImplicitNone Integer (c_int), Intent (inch), Value:: N Integer (C_int), Intent (inch):: Array (n) End Function integer (c_int) function Func2 (PT, N) bind (c, name="Test") ImportImplicitNone Integer (c_int), Intent (inch), Value:: N Type (c_ptr), Value:: Pt end FunctionEndInterfacetype (c_ptr):: A1integer (C_int), Target:: ABC (5) Integer:: Iabc= [ A, A, *, the, One]A1= C_loc (ABC (1))!Pass Array Directlyi=func (ABC, size (ABC))!Pass Addressi= Func2 (C_loc (ABC (1)),5)! PassNULLPointeri= Func2 (C_null_ptr,5)! PassNULLfunction Pointeri= Func2 (C_null_funptr,5) End Program

Gfortran code_c.c code_for.f90-o Test

Operation Result:

array[1]=12array[2]=12array[3]=35array[4]=67array[5]=11
array[1]=12array[2]=12array[3]=35array[4]=67array[5]=11
This is null pointer
This is null pointer

　　

FORTRAN passes null values to C