5.12.32 The WEAK Pragma

The WEAK pragma gives weak binding to a symbol.

The syntax of the pragma in C is:

The syntax of the pragma in C++ is:

The WEAK pragma makes symbol a weak reference if it is a reference, or a weak definition, if it is a definition. The symbol can be a data or function variable. In effect, unresolved weak references do not cause linker errors and do not have any effect at run time. The following apply for weak references:

• Libraries are not searched to resolve weak references. It is not an error for a weak reference to remain unresolved.
• During linking, the value of an undefined weak reference is:
  • Zero if the relocation type is absolute
  • The address of the place if the relocation type is PC-relative
  • The address of the nominal base address if the relocation type is base-relative.

A weak definition does not change the rules by which object files are selected from libraries. However, if a link set contains both a weak definition and a non-weak definition, the non-weak definition is always used.

The WEAK pragma has the same effect as using the weak function or variable attribute. See Section 5.17.2 and Section 5.17.3, respectively.