与GHC连接

Question

我在跟踪这个短教程

并尝试使用GHC (格拉斯哥Haskell编译器，Version 7.10.1)编译Webots应用程序(用C编写)，命令如下：

ghc --make -no-hs-main -optc-O 
-I"/Applications/Webots/include/controller/c/" 
-L"/Applications/Webots/lib/" 
-outputdir build/release/ 
advanced_genetic_algorithm_supervisor.c 
Safe 
-o advanced_genetic_algorithm_supervisor

并在链接阶段获得以下错误：

Linking advanced_genetic_algorithm_supervisor ...
Undefined symbols for architecture x86_64:
  "_wb_display_draw_text", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_display_get_height", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_display_get_width", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_emitter_send", referenced from:
      _evaluate_genotype in advanced_genetic_algorithm_supervisor.o
  "_wb_receiver_enable", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_receiver_get_data", referenced from:
      _check_for_slaves_data in advanced_genetic_algorithm_supervisor.o
  "_wb_receiver_get_queue_length", referenced from:
      _check_for_slaves_data in advanced_genetic_algorithm_supervisor.o
  "_wb_receiver_next_packet", referenced from:
      _check_for_slaves_data in advanced_genetic_algorithm_supervisor.o
  "_wb_robot_cleanup", referenced from:
      _run_optimization in advanced_genetic_algorithm_supervisor.o
  "_wb_robot_get_basic_time_step", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_robot_get_device", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_robot_init", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_robot_step", referenced from:
      _run_seconds in advanced_genetic_algorithm_supervisor.o
      _evaluate_genotype in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_field_get_sf_rotation", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_field_get_sf_vec3f", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_field_set_sf_rotation", referenced from:
      _evaluate_genotype in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_field_set_sf_vec3f", referenced from:
      _evaluate_genotype in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_node_get_field", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
  "_wb_supervisor_node_get_from_def", referenced from:
      _main in advanced_genetic_algorithm_supervisor.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我认为这意味着编译器无法找到函数(“符号”)，尽管它能够通过编译过程解析所有使用-I路径在程序中指定的内容。

Answer 1

这意味着链接器找不到那些函数/符号，因为您没有告诉它链接到Webots库。

您需要添加-lsomething，假设库文件名为/Applications/Webots/lib/libsomething.dylib (或libsomething.a)。