![]() ![]() Although, it did take some time, it was much easier than adding dll markup to every source file. Real World Use CasesĪfter adding this feature to CMake, I tried it on two relatively large software projects VXL ( ( ) and ITK ( ). See the generated mylibary_export.h for more details. Note, if you use GenerateExportHeader and still want static builds to work, you will need to add a -Dmylibrary_STATIC during static builds. Static mylibrary_EXPORT int GlobalCounter The easiest way to handle the global data is to use the CMake GenerateExportHeader module like this: add_library(mylibrary $) If you run into undefined symbols, check for global data like static data members of classes. If there are no global data variables in the project, all libraries will be built as DLLs with no errors. This should turn all add_library calls that do not explicitly specify build type into shared builds. To try this out on an existing project, run cmake -DCMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=TRUE -DBUILD_SHARED_LIBS=TRUE This property is initialized by the value of the CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS variable when a target is created. ![]() This simplifies porting projects to Windows by reducing the need for explicit dllexport markup, even in C++ classes. All other function symbols will be automatically exported and imported by callers. ![]() The symbol is exported from the DLL correctly and automatically, but the compiler needs to know that it is being imported from a DLL at compile time. For global data symbols, _declspec(dllimport) must still be used when compiling against the code in the DLL. def file will be passed to the linker causing all symbols to be exported from the DLL. obj files for a SHARED library on Windows. def file with all symbols found in the input. When enabled, this property causes CMake to automatically create a. The feature is implemented in CMake via a new target property, WINDOWS_EXPORT_ALL_SYMBOLS. def file automatically, in most cases without needing to modify the original source code. obj files that will make up a DLL and create a. CMake now has a feature which allows it to query. However, with a large existing C++ code base, it can be difficult and time consuming to edit all of the source code. The standard workaround uses the preprocessor to conditionally insert _declspec(import) and _declspec(export) into the code. However, with C++ code, name mangling and the sheer number of functions make crafting a. def file by hand or automatically is not very difficult since you just have to list the names of all the functions in the library. On Windows, you must either use compiler directives _declspec(import) and _declspec(export) to declare which symbols are exported/imported from a shared library, or you must create a module definition text file (.def) with a list of all the symbols you want to export and pass that file to the linker. The compilers on Linux/UNIX have the ability to export all symbols in a shared library automatically. Linux/UNIX developers are often surprised to learn that creating a shared library on Windows known as a DLL (dynamic linked library) requires changes to the source code or an explicit listing of all the symbols that the dll will export. CMake 3.4 will have a new feature to simplify porting C and C++ software using shared libraries from Linux/UNIX to Windows. ![]()
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