To create a shared object (.so) file from one or more object files on Unix-like operating systems (including Linux and macOS), you typically use the gcc or g++ compiler (for C or C++ projects, respectively) with the -shared option. This tells the compiler to produce a shared library rather than an executable. Here's how you do it:
This command will take object files file1.o, file2.o, and file3.o and combine them into a shared object file named libmyshared.so.
Additional Considerations:
Position Independent Code (PIC): When compiling the source files into object files that will be used in a shared library, it's often recommended (or required) to compile them with the -fPIC option, which generates position-independent code. This makes the resulting shared library more flexible in terms of where it can be loaded into memory, which is important for shared libraries. The compilation step for each source file would look something like this:
Library Naming Convention: It's a common convention to prefix the name of shared libraries with lib and use the .so extension. This helps tools like the dynamic linker (ld.so) and compilers (gcc, g++) recognize and handle them appropriately.
Linking with Other Libraries: If your shared library depends on other shared libraries, you can specify them using the -l (lowercase L) option followed by the library name (without the lib prefix and .so extension). You may also need to specify the path to these libraries with -L.
Visibility: Consider using visibility attributes or pragmas to control which symbols are exported from your shared library. By default, all symbols may be exported, but it's often a good practice to limit exports to only those symbols that should be publicly available.
Here is an example command that compiles source files directly into a shared object, assuming the source files do not depend on other shared libraries:
use ld instead of gcc?
To create a shared object (
.so) file from one or more object files on Unix-like operating systems (including Linux and macOS), you typically use thegccorg++compiler (for C or C++ projects, respectively) with the-sharedoption. This tells the compiler to produce a shared library rather than an executable. Here's how you do it:This command will take object files
file1.o,file2.o, andfile3.oand combine them into a shared object file namedlibmyshared.so.Additional Considerations:
Position Independent Code (PIC): When compiling the source files into object files that will be used in a shared library, it's often recommended (or required) to compile them with the
-fPICoption, which generates position-independent code. This makes the resulting shared library more flexible in terms of where it can be loaded into memory, which is important for shared libraries. The compilation step for each source file would look something like this:Library Naming Convention: It's a common convention to prefix the name of shared libraries with
liband use the.soextension. This helps tools like the dynamic linker (ld.so) and compilers (gcc,g++) recognize and handle them appropriately.Linking with Other Libraries: If your shared library depends on other shared libraries, you can specify them using the
-l(lowercase L) option followed by the library name (without thelibprefix and.soextension). You may also need to specify the path to these libraries with-L.Visibility: Consider using visibility attributes or pragmas to control which symbols are exported from your shared library. By default, all symbols may be exported, but it's often a good practice to limit exports to only those symbols that should be publicly available.
Here is an example command that compiles source files directly into a shared object, assuming the source files do not depend on other shared libraries:
Remember, the exact command and options might vary depending on your specific development environment and the languages you're using.