对同一模块中定义的过程的未定义引用 [英] Undefined reference to procedure defined in the same module

问题描述

我正在尝试熟悉 fortran 中的模块，为此我创建了一个带有模块的简单代码.附上源代码.

I am trying to get familiarize with modules in fortran and for that I have created a simple code with module. The source code is attached.

主程序

program main_prog
  use mod_f_g_h
  !
  implicit none
  ! f,g,h,s are defined in mod_f_g_h
  real :: x,y
  !
  ! read x,y
  print *, "enter x and y "
  read*, x, y
  !
  ! check
  if( y == 0 ) then
    print*, "y must be non-zero"
    stop
  end if
  !
  ! print on screen
  print*, '  x   = ', x
  print*, '  y   = ', y
  print*, 'x + y = ', f(x,y)
  print*, 'x * y = ', g(x,y)
  print*, 'x * x = ', s(x)
  print*, 'y * y = ', s(y)
  print*, 'x / y = ', h(x,y)

end program main_prog

模块

module mod_f_g_h
  !
  ! use other modules
  implicit none
  !
contains
  !
  real function s(x)
    implicit none
    real :: x,g
    s = g(x,x)
  end function s
  !
  real function f(x,y)
    implicit none
    real :: x,y
    f = x+y
  end function f
  !
  real function g(x,y)
    implicit none
    real :: x,y
    g = x*y
  end function g
  !
  real function h(x,y)
    implicit none
    real :: x,y
    h = x/y
  end function h
end module mod_f_g_h

但是当我尝试编译和链接代码时，使用

But when I try to compile and link the code, using

gfortran -c mod_f_g_h.f90
gfortran -c main.f90
gfortran *.o -o run.x

出现以下错误(在最后一步)

Got the following error (in last step)

mod_f_g_h.o: In function `__mod_f_g_h_MOD_s':
mod_f_g_h.f90:(.text+0xb6): undefined reference to `g_'
collect2: ld returned 1 exit status

我想，我已经定义了所有的变量，而且我没有链接任何外部库，所以我不知道为什么会出现这个错误?有什么意见/想法吗?

I think, I have defined all the variables, moreover I am not linking any external library, so I don't know why this error is appearing? Any comment/idea?

推荐答案

应该阅读

real function s(x)
implicit none
real :: x
s = g(x,x)
end function s

模块内部.

VladimirF 的进一步解释:

Further explanation by VladimirF:

通过real g，您将s 内的g 函数声明为一个external 真实函数，与此不同模块中的一个.

By real g you were declaring the function g inside s as an external real function distinct from that one in the module.

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