c++ - CMAKE 链接外部 c 库

Question

您好，基本上我正在尝试使用来自 here 的 svm .它是用 C 编写的，并给出了如何在 C++ 中使用它的说明:

• Compile "svm_learn.c", "svm_common.c", and "svm_hideo.c" as
  C code.

• The C++ program you want to call svm_learn/8 and classify_example/2 (or classify_example_linear/2) from needs to include the following headers:

  extern "C" { # include "svm_common.h" # include "svm_learn.h" }

• Link "svm_learn.o", "svm_common.o", and "svm_hideo.o" to your program.

所以我编译了上述文件并获得了所需的 .o 文件。比我补充的:

SET( svm_lib_light_obj
    E:\framework\svm_light\build\svm_learn.o
    E:\framework\svm_light\build\svm_common.o
    E:\framework\svm_light\build\svm_hideo.o
)

ADD_LIBRARY(
    svm_lib_light
    STATIC
    EXCLUDE_FROM_ALL
    ${svm_lib_light_obj}
)

SET_SOURCE_FILES_PROPERTIES(
  ${svm_lib_light_obj}
  PROPERTIES
  EXTERNAL_OBJECT true # to say that "this is actually an object file, so it should not be compiled, only linked"
  GENERATED true       # to say that "it is OK that the obj-files do not exist before build time"
  )

SET_TARGET_PROPERTIES(
  svm_lib_light
  PROPERTIES
  LINKER_LANGUAGE C # Or else we get an error message, because cmake can't figure out from the ".o"-suffix that it is a C-linker we need.
  ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/lib
  )

所以现在我只需要包含提到的 .h 文件。我将它们添加到我的其他源文件中:

ADD_EXECUTABLE ( MYProgramm
            ...
            #other source files
            ...
            src/svm_common.h
            src/svm_learn.h
)

不幸的是，它不起作用。从这些 .h 文件调用任何函数会导致链接器错误 LNK2001、LNK1120。我猜我必须告诉 cmake 这些 .h 文件是 .o 文件的前端。但是如何呢？

Answer 1

最好的方法是将这些 C 文件添加到您的项目中:

SET(SVM_LIGHT_SRC_DIR "E:/framework/svm_light")

INCLUDE_DIRECTORIES(${SVM_LIGHT_SRC_DIR})

ADD_LIBRARY(
    svm_lib_light
    ${SVM_LIGHT_SRC_DIR}/svm_learn.c
    ${SVM_LIGHT_SRC_DIR}/svm_common.c
    ${SVM_LIGHT_SRC_DIR}/svm_hideo.c
)

ADD_EXECUTABLE ( MYProgramm
            ...
            #other source files
            ...
)

TARGET_LINK_LIBRARIES(MYProgram svm_lib_light)