# WINDOWS_EXPORT_ALL_SYMBOLS

Added in version 3.4.

This property is implemented only for MS-compatible tools on Windows.

Enable this boolean property to automatically create a module definition (`.def`) file with all global symbols found in the input `.obj` files for a `SHARED` library (or executable with `ENABLE_EXPORTS`) on Windows. The module definition file will be passed to the linker causing all symbols to be exported from the `.dll`.

This simplifies porting projects to Windows by reducing the need for explicit `dllexport` markup, even in `C++` classes. Function symbols will be automatically exported and may be linked by callers. However, there are some cases when compiling code in a consumer may require explicit `dllimport` markup:

- Global data symbols must be explicitly marked with `__declspec(dllimport)` in order to link to data in the `.dll`.

- In cases that the compiler generates references to the virtual function table, such as in a delegating constructor of a class with virtual functions, the whole class must be marked with `__declspec(dllimport)` in order to link to the vftable in the `.dll`.

- See the MSVC Linker /EXPORT Option for more information on data symbols.

When this property is enabled, zero or more `.def` files may also be specified as source files of the target. The exports named by these files will be merged with those detected from the object files to generate a single module definition file to be passed to the linker. This can be used to export symbols from a `.dll` that are not in any of its object files but are added by the linker from dependencies (e.g. `msvcrt.lib`).

This property is initialized by the value of the `CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS` variable if it is set when a target is created.