Question

Hi basicly i am trying to use the svm from here . It is written in C and gives instructions how to use it in c++:

• 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.

So i compiled the mentioned files and got the needed .o files.
Than i added:

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
  )

So now i just need to include the .h files mentioned. I added them to my other source files in:

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

Unfortunatly it doesnt work. Calling any function from these .h files leads to an linker error LNK2001, LNK1120.
I am guessing i have to tell cmake that these .h files are frontends for the .o files. But how?

Answer 1

The best way would be to add those C files to your project:

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)