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What occurs when the linker encounters duplicate symbol names?
Duplicate symbols When two or more functions in the linked object files have the same name, a warning message is issued.
Shared libraries (also called dynamic libraries) are linked into the program in two stages. First, during compile time, the linker verifies that all the symbols (again, functions, variables and the like) required by the program, are either linked into the program, or in one of its shared libraries.
Are multiple weak symbols with the same name allowed?
Uninitialized global variables get weak symbols. Rule 1: Multiple strong symbols (with same variable name) are not allowed.
What is meant by linker?
In computing, a linker or link editor is a computer system program that takes one or more object files (generated by a compiler or an assembler) and combines them into a single executable file, library file, or another “object” file.
What is a weak attribute?
The weak attribute causes the declaration to be emitted as a weak symbol rather than a global. This is primarily useful in defining library functions which can be overridden in user code, though it can also be used with non-function declarations.
What is linker and its types?
Linker is a program in a system which helps to link a object modules of program into a single object file. Linker are also called link editors. Linking is process of collecting and maintaining piece of code and data into a single file. Linker also link a particular module into system library.
What are the symbols of a shared library?
But: a shared library has two symbol tables: a static symbol table .symtab, like an object file, plus a dynamic symbol table, .dynsym, used by the loader for run-time symbol resolution.
Are there duplicate symbols in the dynamic symbol table?
So in reality, there are no duplicated symbols in the dynamic symbol table: the sneaky many-to-one nature of the name-demangling mapping just makes it look that way. But why? I’m afraid the answer to that is too long and complicated for here.
That library has a main () function or equivalent entry point, and was compiled in such a way that it is useful both as an executable and as a shared object. Here’s one suggestion about how to do this, although it does not work for me.
When you link object files into a shared library, the linker by default transcribes the GLOBAL symbols from their .symtab s into the .symtab and the .dynsym of the shared library, except for those symbols that have HIDDEN visibility in the object files (which they get from being defined with the attribute of hidden visibility at compilation).