What is the benefit of declaring a symbol as weak?

This behavior allows an executable to override standard library functions, such as malloc(3). When linking a binary executable, a weakly declared symbol does not need a definition. In comparison, (by default) a declared strong symbol without a definition triggers an undefined symbol link error.

What does pragma weak mean?

#pragma weak symbol. This pragma declares symbol to be weak, as if the declaration had the attribute of the same name. The pragma may appear before or after the declaration of symbol , but must appear before either its first use or its definition. It is not an error for symbol to never be defined at all.

What is strong symbol in C?

c , we define a strong symbol gvar and it is initialized to 5. In main. c , we only define the variable gvar , and it is a weak symbol. When we compile the program using GCC, the gvar in main.

What is __ attribute __ in C?

The keyword __attribute__ allows you to specify special properties of variables, function parameters, or structure, union, and, in C++, class members. Some attributes are currently defined generically for variables. Other attributes are defined for variables on particular target systems.

What is weak attribute in C?

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 strong and weak symbols in C?

A weak symbol denotes a specially annotated symbol during linking of Executable and Linkable Format (ELF) object files. By default, without any annotation, a symbol in an object file is strong. During linking, a strong symbol can override a weak symbol of the same name.

What is __ weak?

__weak. This keyword instructs the compiler to export symbols weakly. The __weak keyword can be applied to function and variable declarations, and to function definitions.

What is __ weak Objective C?

__weak specifies a reference that does not keep the referenced object alive. A weak reference is set to nil when there are no strong references to the object.