问题
I am building a shared library on Ubuntu 9.10. I want to export only a subset of my functions from the library. On the Windows platform, this would be done using a module definition (.def) file which would contain a list of the external and internal names of the functions exported from the library.
I have the following questions:
How can I restrict the exported functions of a shared library to those I want (i.e. a .def file equivalent)
Using .def files as an example, you can give a function an external name that is different from its internal name (useful for prevent name collisions and also redecorating mangled names etc)
On windows I can use the EXPORT command (IIRC) to check the list of exported functions and addresses, what is the equivalent way to do this on Linux?
回答1:
The most common way to only make certain symbols visible in a shared object on linux is to pass the -fvisibility=hidden to gcc and then decorate the symbols that you want to be visible with __attribute__((visibility("default"))).
If your looking for an export file like solution you might want to look at the linker option --retain-symbols-file=FILENAME which may do what you are looking for.
I don't know an easy way of exporting a function with a different name from its function name, but it is probably possible with an elf editor. Edit: I think you can use a linker script (have a look at the man page for ld) to assign values to symbols in the link step, hence giving an alternative name to a given function. Note, I haven't ever actually tried this.
To view the visible symbols in a shared object you can use the readelf command. readelf -Ds if I remember correctly.
回答2:
How can I restrict the exported functions of a shared library to those I want (i.e. a .def file equivalent)
Perhaps you're looking for GNU Export Maps or Symbol Versioning
g++ -shared spaceship.cpp -o libspaceship.so.1
-Wl,-soname=libspaceship.so.1 -Wl,
--version-script=spaceship.expmap
回答3:
gcc also supports the VC syntax of __declspec(dllexport). See this.
回答4:
Another option is to use the strip command with this way:
strip --keep-symbol=symbol_to_export1 --keep-symbol=symbol_to_export2 ... \
libtotrip.so -o libout.so
来源：https://stackoverflow.com/questions/2839504/is-there-a-def-file-equivalent-on-linux-for-controlling-exported-function-names