LS,
I'm trying to build a static and dynamic library that can be used to link with both dynamically and static. I would like the library to run on as many platforms as possible no matter the compiler used. In order to build the library and a few test programs I'm using CMake to build the library eeg on Linux and on windows using g++ and MSVC++ respectively.
On Linux both the dynamic and static libraries seem to work as I suspected, on windows the .dll seems to link perfectly and my test programs run. However, a program using the static library complains about linking errors. I really miss the point what I'm doing wrong, It could be something in my CMakeLists.txt, but also in the Setup of my library. Below I've made a minimal program that uses my library that demonstrates the issues I'm experiencing. The library consists of two C++ files, an C API that exports the code in the C++ files, a C++ program that uses the C API and finally a CMakeList.txt that can build all programs but the program that uses the static library. This all to yields a wonderfull "Hello, World!".
I know I show a lot of code, but at least it is a minimal project that demonstrates my problems with linking to the static library. I hope someone is kind enough to take a look at this project and explain me what I'm doing wrong.
Kind regards,
hetepeperfan
The C++ file PriCpp.cpp
#include "PriCpp.h"
using namespace std;
string PriMessageBuilder::message() const {
return "Hello, World!";
}
The header PriCpp.h
#ifndef PRICPP_H
#define PRICPP_H
#include <string>
class PriMessageBuilder{
public:
std::string message() const;
};
#endif
The C API is: mycapi.h
#ifndef MYCAPI_H
#define MYCAPI_H
#include "builder_export.h"
#ifdef __cplusplus
extern "C" {
#endif
typedef struct {} message_builder;
BUILDER_EXPORT message_builder* message_builder_new();
BUILDER_EXPORT void message_builder_destroy(
message_builder* builder
);
BUILDER_EXPORT char* message_builder_message(
message_builder* builder
);
#ifdef __cplusplus
}
#endif
#endif
mycapi.cpp is:
#include "mycapi.h"
#include "PriCpp.h"
#include <cstring>
#include <cstdlib>
message_builder* message_builder_new() {
PriMessageBuilder* ret = NULL;
try {
ret = new PriMessageBuilder();
} catch (...) {
}
return reinterpret_cast<message_builder*>(ret);
}
void message_builder_destroy(message_builder* builder)
{
PriMessageBuilder* b = reinterpret_cast<PriMessageBuilder*>(builder);
delete b;
}
char* message_builder_message(message_builder* builder)
{
PriMessageBuilder* b = reinterpret_cast<PriMessageBuilder*>(builder);
return strdup(b->message().c_str());
}
The program that I use in combination with the library above. program.cpp
#include <iostream>
#include <cstdlib>
#include <string>
#include "mycapi.h"
using namespace std;
class MessageBuilder {
public:
MessageBuilder() : m_builder(message_builder_new()) {
}
~MessageBuilder() {
message_builder_destroy(m_builder);
}
string MessageBuilder::message() {
char* msg = message_builder_message(m_builder);
string m(msg);
free (msg);
return m;
}
private:
message_builder* m_builder;
};
int main(int, char**) {
MessageBuilder m;
cout << m.message() << endl;
return 0;
}
and finally CMakeLists.txt to build a makefile or a visual studio solution
#setting up project
cmake_minimum_required(VERSION 2.6)
project(libbuilder CXX)
include (GenerateExportHeader)
include_directories("${PROJECT_BINARY_DIR}")
#creating library
add_library(builder SHARED PriCpp.cpp PriCpp.h mycapi.cpp mycapi.h)
add_library(builder-static STATIC PriCpp.cpp PriCpp.h mycapi.cpp mycapi.h)
generate_export_header(builder)
set_target_properties(builder PROPERTIES COMPILE_FLAGS -DBUILD_BUILDER_SHARED)
set_target_properties(builder-static PROPERTIES COMPILE_FLAGS -DBUILDER_STATIC_DEFINE)
#creating programs
add_executable(program program.cpp)
add_executable(program-static program.cpp)
target_link_libraries(program builder)
target_link_libraries(program-static builder-static)
If I build the solution I get these linker errors:
1>program.obj : error LNK2019: unresolved external symbol __imp__message_builder_new referenced in function "public: __thiscall MessageBuilder::MessageBuilder(void)" (??0MessageBuilder@@QAE@XZ)
1>program.obj : error LNK2019: unresolved external symbol __imp__message_builder_destroy referenced in function "public: __thiscall MessageBuilder::~MessageBuilder(void)" (??1MessageBuilder@@QAE@XZ)
1>program.obj : error LNK2019: unresolved external symbol __imp__message_builder_message referenced in function "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __thiscall MessageBuilder::message(void)" (?message@MessageBuilder@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ)
1>K:\duijn119\programming\cmake\staticsharedlib\build\Debug\program-static.exe : fatal error LNK1120: 3 unresolved externals
The CMake generated include header is:
#ifndef BUILDER_EXPORT_H
#define BUILDER_EXPORT_H
#ifdef BUILDER_STATIC_DEFINE
# define BUILDER_EXPORT
# define BUILDER_NO_EXPORT
#else
# ifndef BUILDER_EXPORT
# ifdef builder_EXPORTS
/* We are building this library */
# define BUILDER_EXPORT __declspec(dllexport)
# else
/* We are using this library */
# define BUILDER_EXPORT __declspec(dllimport)
# endif
# endif
# ifndef BUILDER_NO_EXPORT
# define BUILDER_NO_EXPORT
# endif
#endif
#ifndef BUILDER_DEPRECATED
# define BUILDER_DEPRECATED __declspec(deprecated)
#endif
#ifndef BUILDER_DEPRECATED_EXPORT
# define BUILDER_DEPRECATED_EXPORT BUILDER_EXPORT BUILDER_DEPRECATED
#endif
#ifndef BUILDER_DEPRECATED_NO_EXPORT
# define BUILDER_DEPRECATED_NO_EXPORT BUILDER_NO_EXPORT BUILDER_DEPRECATED
#endif
#define DEFINE_NO_DEPRECATED 0
#if DEFINE_NO_DEPRECATED
# define BUILDER_NO_DEPRECATED
#endif
#endif
