M1芯片Mac用gfortran编译NetCDF代码出现arm64未定义符号错误

我是搭载M1芯片的Mac用户，尝试使用gfortran创建NetCDF文件时出现错误。以下是编写的Fortran代码：

PROGRAM net2
     use netcdf

     IMPLICIT NONE

     INTEGER :: status, ncid
     INTEGER :: nx, ny, ii, jj, x, y, xx, yy
     REAL, DIMENSION(239, 239) :: field
     REAL, DIMENSION(239, 239) :: eqa
     INTEGER :: dimid_lon, dimid_lat, dimid_time
     INTEGER :: varid_lat, varid_lon, varid_field, varid_eqa, varid_time
     REAL :: pi, lat_array(239), lon_array(239)
     PARAMETER (pi = 4.0 * atan(1.0))

     status = nf90_create('new.nc', NF90_NETCDF4, ncid)
     call check(status, 'open')

     nx = 239
     ny = 239

     status = nf90_def_dim(ncid, 'longitude', nx, dimid_lon)
     status = nf90_def_dim(ncid, 'latitude', ny, dimid_lat)
     status = nf90_def_dim(ncid, 'time', nf90_unlimited, dimid_time)

     status = nf90_def_var(ncid, 'longitude', NF90_FLOAT, [dimid_lon], varid_lon)
     status = nf90_def_var(ncid, 'latitude', NF90_FLOAT, [dimid_lat], varid_lat)
     status = nf90_def_var(ncid, 'time', NF90_FLOAT, [dimid_time], varid_time)
     status = nf90_def_var(ncid, 'field', NF90_FLOAT, [dimid_lat, dimid_lon], varid_field)
     status = nf90_def_var(ncid, 'eqa', NF90_FLOAT, [dimid_lat, dimid_lon], varid_eqa)

     status = nf90_put_att(ncid, NF90_GLOBAL, 'note', 'Test of Created NetCDF file')
     status = nf90_put_att(ncid, NF90_GLOBAL, 'ISIC', 15)
     status = nf90_put_att(ncid, varid_lon, 'units', 'degree_east')
     status = nf90_put_att(ncid, varid_lat, 'units', 'degree_north')
     status = nf90_put_att(ncid, varid_field, '_FillValue', -2e8)
     status = nf90_put_att(ncid, varid_eqa, '_FillValue', -2e8)

     lat_array = [(jj * (360./ny), jj=0, ny-1)]
     lon_array = [((ii * (180./(nx-1)) - 90.), ii=0, nx-1)]
     do jj = 1, ny
             do ii = 1, nx
             field(ii, jj) = sin(lon_array(ii) * pi/180.) * cos(lat_array(jj) * pi/180.)
             end do
     end do

     do yy = 1, ny
             do xx = 1, nx
                     eqa(xx, yy) = x**2 + y**2
             end do
     end do

     status = nf90_put_var(ncid, varid_lon, lon_array)
     status = nf90_put_var(ncid, varid_lat, lat_array)
     status = nf90_put_var(ncid, varid_field, field)
     status = nf90_put_var(ncid, varid_eqa, eqa)

     status = nf90_close(ncid)
     call check(status, 'close')

contains
     SUBROUTINE check(status, loc)
             INTEGER, INTENT(in) :: status
             CHARACTER, INTENT(in) :: loc
             if (status /= NF90_NOERR) then
             WRITE(*, *) "ERROR at", loc
             WRITE(*, *) NF90_STRERROR(status)

             end if
     END SUBROUTINE check
END PROGRAM net2

编译该代码后出现如下错误：

Undefined symbols for architecture arm64:
  "___netcdf_MOD_nf90_close", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_create", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_def_dim", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_def_var_manydims", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_put_att_one_fourbyteint", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_put_att_one_fourbytereal", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_put_att_text", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_put_var_1d_fourbytereal", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_put_var_2d_fourbytereal", referenced from:
      _MAIN__ in ccHtjGFn.o
  "___netcdf_MOD_nf90_strerror", referenced from:
      _check.0 in ccHtjGFn.o
ld: symbol(s) not found for architecture arm64
collect2: error: ld returned 1 exit status

我在Windows环境从未遇到过此类错误，不知该如何解决。

这类错误是链接器找不到NetCDF Fortran库的符号导致的，本质是编译时没有正确链接NetCDF相关库文件，M1 Mac的arm64架构下需要确保库和编译器的架构匹配，同时正确指定链接参数。

步骤1：确认NetCDF库的安装情况 #

如果是用Homebrew安装的NetCDF和NetCDF-Fortran，执行以下命令确认安装路径：

brew list netcdf
brew list netcdf-fortran

确保安装的是arm64架构的版本（Homebrew在M1 Mac默认安装arm64版本，若之前用Rosetta安装的x86版本，需要卸载后重新安装）。

步骤2：正确编译链接代码 #

编译时需要指定NetCDF-Fortran的库路径和链接库，使用nf-config工具获取正确的编译参数：

gfortran net2.f90 -o net2 $(nf-config --fflags --flibs)

如果nf-config不可用，可手动指定路径（以Homebrew默认安装路径为例）：

gfortran net2.f90 -o net2 -I/opt/homebrew/include -L/opt/homebrew/lib -lnetcdff -lnetcdf

根据实际安装路径调整-I和-L后的路径。

步骤3：修复代码中的未定义变量问题 #

代码中eqa(xx, yy) = x**2 + y**2一行的x和y未定义，运行时会触发错误，建议修改为：

eqa(xx, yy) = real(xx)**2 + real(yy)**2

内容的提问来源于stack exchange，提问作者이수현