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A shared library is a file containing object code that several a. out files may use simultaneously while executing. When a program is link edited with a shared library, the library code that defines the program’s external references is not copied into the program’s object file. Instead, a special section called .
What is the difference between a static and shared library?
Static libraries, while reusable in multiple programs, are locked into a program at compile time. Dynamic, or shared libraries on the other hand, exist as separate files outside of the executable file.
Why do we need shared libraries in addition to static ones?
The idea behind shared libraries is to have only one copy of commonly used routines and to maintain this common copy in a unique shared-library segment. These common routines can significantly reduce the size of executable programs, thereby saving disk space.
What is the difference between dynamic and static linking?
Static linking includes the files that the program needs in a single executable file. Dynamic linking is what you would consider the usual, it makes an executable that still requires DLLs and such to be in the same directory (or the DLLs could be in the system folder).
Why is it important to have shared libraries?
Shared libraries are useful in sharing code which is common across many applications. For example, it is more economic to pack all the code related to TCP/IP implementation in a shared library. However, data can’t be shared as every application needs its own set of data.
Conversely, when you create a shared library, you only create the library with a specific filename (with more detailed version information).
How to override functions in a shared library?
If you want to just override a few functions in a library, but keep the rest of the library, you can enter the names of overriding libraries (.o files) in /etc/ld.so.preload; these “preloading” libraries will take precedence over the standard set.
What does the soname of a shared library mean?
Every shared library has a special name called the “soname”. The soname has the prefix “lib”, the name of the library, the phrase “.so”, followed by a period and a version number that is incremented whenever the interface changes (as a special exception, the lowest-level C libraries don’t start with “lib”).
Every shared library also has a “real name”, which is the filename containing the actual library code. The real name adds to the soname a period, a minor number, another period, and the release number.